# Bonsia ~ Testing Depth of Field



## PJcam (Jan 16, 2018)

The weather is abysmal, heavy rain and hail, strong winds and going to get much stronger. So as a 'beginner' I thought it was time to experiment with the camera and learn a little more, having done so, now it's time to ask for your comments.

The aim of this lesson I gave myself was to try get the best image I could, in bad light, without flash and with a narrow depth of field, from just before the bonsia to just past the blinds and glass which has rain running down.  I included the vertical blinds at a slight angle, my thoughts were to include reflection from the blinds and also to fade the image behind the set field.




 

The image was in Raw format, converted to Jpg using instant Jpg from raw software, (Good Free software), but as it was to large to upload, just over 2mb, I resized it in Adobe Photoshop which crashed the image down to just over 800kb, I hope this doesn't spoil the image quality to mush. I am not sure what is the largest Jpg file we can upload on here?

I welcome comments good and bad. I realise I could have taken the image portrait instead of landscape, but this way showed a little more rain on the glass behind the blinds.

Camera - Canon EOS Rebel T6 1300D, 
Lens - Canon EF-S 75-300 mm f/3.5-5.6
Settings - Shutter 1/200 sec,  Aperture f/4.5,  ISO 1600, Lens set at 130.00mm


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## jcdeboever (Jan 16, 2018)

Good lesson. Your on the right track. Looks like it is pretty thin DOF. Keep track at what point the subject is all in focus with good separation. Know and understand where that threshold is, especially since a lot of lenses don't have the markings. Show us good, better, best. I'd post this in beginners forum moving forward. Some really smart people pay close attention to that thread to help you expedite the learning curve.

I have done this by placing white craft paper on a table, and with a sharpie, map out the distance points on the paper, and place objects in a row. There are DOF calculators online to help guide you as well, some lenses have the marks already on them. 

P.S. @terri , I'd move this to the beginners forum.


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## jcdeboever (Jan 16, 2018)

@PJcam, I have a real good lesson on DOF in a John Hedgecoe book. If I can remember, I will try and copy it for you and post in this thread when I get home tonight.


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## PJcam (Jan 16, 2018)

jcdeboever said:


> Good lesson. Your on the right track. Looks like it is pretty thin DOF. Keep track at what point the subject is all in focus with good separation. Know and understand where that threshold is, especially since a lot of lenses don't have the markings. Show us good, better, best. I'd post this in beginners forum moving forward. Some really smart people pay close attention to that thread to help you expedite the learning curve.
> 
> P.S. @terri , I'd move this to the beginners forum.



Thanks jcdeboever, I did take a number of shots and recorded in my note book the settings of each, the first trial ran images with changed shutter speeds, aperture and ISO, the second set was taking a fixed aperture f/4.5 and changing the other two setting to see the field change. I soon picked up that the lower the F-Stop the tighter the depth of field, this is all new to me but very fascinating, and quite rewarding.

I will see if I can add some images as you have mentioned.

Being a 'beginner' there is so much to learn, and once I learn I realise comes practice, practice, practice, then experience with time and practice. To help me from what I read so far and seen on video I created this... I think I got right. I stuck it in the front of my note book for reference till it is all in my head.


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## jcdeboever (Jan 16, 2018)

Awesome @PJcam. This really will expedite things along.


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## PJcam (Jan 16, 2018)

jcdeboever said:


> Awesome @PJcam. This really will expedite things along.



I must admit the more I tried to learn Shutter Speed, Aperture and ISO, I kept confusing myself with the High and Lows of the F-Stops, compared to aperture openings, whilst also trying to get ,my head round which way the DoF worked, but I them found I had all tables the same way and ISO works opposite to the other two. I am getting there. The only way (for me) was sit down write it down and then make an image with notes for my note book. We all learn different ways.


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## jcdeboever (Jan 16, 2018)

PJcam said:


> jcdeboever said:
> 
> 
> > Awesome @PJcam. This really will expedite things along.
> ...



For ISO, I simply think of it as a way to gain shutter speed. I use it for low light, like to double the focal length so bumping the ISO will get me there (i'm pretty shaky at times). Or for sports when I want to freeze fast movement. Some lenses have stabilization that helps keep that double focal length thing less drastic. Of course you should really find out the threshold of what you deem acceptable as far as noise level. For example, I find my Fujifilm cameras acceptable up to ISO 6400.


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## Ysarex (Jan 16, 2018)

PJcam said:


> The weather is abysmal, heavy rain and hail, strong winds and going to get much stronger. So as a 'beginner' I thought it was time to experiment with the camera and learn a little more, having done so, now it's time to ask for your comments.
> 
> The aim of this lesson I gave myself was to try get the best image I could, in bad light, without flash and with a narrow depth of field, from just before the bonsia to just past the blinds and glass which has rain running down.  I included the vertical blinds at a slight angle, my thoughts were to include reflection from the blinds and also to fade the image behind the set field.
> 
> ...



Practice practice -- very good for you.

A couple comments: The software you used to extract the JPEG did not convert the raw file. It simply extracted the embedded JPEG which was in fact created by the camera. All digital cameras create a JPEG whether you want one or not and whether you set the camera to save one or not. A copy of that JPEG is embedded into the raw file and used to preview the raw file.

Good job with the DOF exercise. As a DOF exercise the photo is fine. 

If you want to consider the photo otherwise then I would suggest your background choice for the bonsai tree is poor and that the tree needs to be lit differently. Thinking in very basic terms we (humans) are drawn to light -- makes sense. We preferentially see light and bright objects and concentrate our interest on those over dark objects. That natural trait makes photographing dark objects against light backgrounds typically unsuccessful. You took a photo of the tree, but when I first look at the photo it takes me too long to make the subject recognition. Not only is the background light compared to the tree it's also very graphic which further demands attention. Re-photograph the tree, get some light on it and find a less graphic and darker background.

Joe


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## Ysarex (Jan 16, 2018)

PJcam said:


> jcdeboever said:
> 
> 
> > Good lesson. Your on the right track. Looks like it is pretty thin DOF. Keep track at what point the subject is all in focus with good separation. Know and understand where that threshold is, especially since a lot of lenses don't have the markings. Show us good, better, best. I'd post this in beginners forum moving forward. Some really smart people pay close attention to that thread to help you expedite the learning curve.
> ...



Your chart raises a few red flags. You watched the toothpaste video and you're showing possible influences from the Triangle Cult. Triangle Cult first: ISO does not control noise in a photograph and increasing ISO does not increase noise. Increasing ISO (especially since you're using a Canon camera) reduces noise. The triangulars are confused about cause and effect. They've attached themselves to a spurious correlation and converted that over to a cause - effect. Noise in a photograph is primarily a function of exposure. Less exposure = more noise and more exposure = less noise. ISO is related: When we don't have enough light to, as JC noted, achieve a fast enough shutter speed then we have to reduce exposure. If we don't have enough light to achieve the aperture we require for DOF then we have to reduce exposure. The noise is a result of reduced exposure. ISO does two things. It biases our camera meter to allow the reduced exposure calculation and then it post processes the sensor capture and brightens the image to compensate for the reduced exposure. In this post processing function ISO typically reduces the noise caused by the underexposure. It may sound like a subtle distinction but it's important to keep cause and effect straight. You can't control noise in a photo with the ISO setting; you have to do that with exposure. Noise is a function of exposure.

Toothpaste: The toothpaste video isn't too bad but it doesn't simplify DOF; if anything it complicates it and confuses some important aspects. It fails to simplify because it doesn't consolidate the different variables into a final simply form that clarifies what's happening. DOF is a function of f/stop and magnification. That's arguably too simple but it's immensely helpful to get to that point for an overall understanding. Subject distance and lens focal length reduce to the variable magnification. From the camera position then f/stop is the only other control available. A critical aspect of DOF that the toothpaste video failed to note was the unequal distribution of DOF. There's more DOF behind the focus plane than in front of the focus plane (can also be expressed as magnification). Here's a graphic that helps:



 

Toothpaste didn't manage to work in the role of Coc (circle of confusion) in the graphics.

With a smaller aperture the DOF increases:



 

With the subject closer to the camera (increase magnification) the DOF decreases.



 

Joe


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## ac12 (Jan 16, 2018)

Bonsai


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## PJcam (Jan 16, 2018)

jcdeboever said:


> For ISO, I simply think of it as a way to gain shutter speed.


Good thinking.



jcdeboever said:


> I use it for low light, like to double the focal length so bumping the ISO will get me there (i'm pretty shaky at times).


Although my hands are alright, I cannot stand for long and find I rock due to pain in my hips and back, I therefore use, tripod or monopod and a plug in lens button.



jcdeboever said:


> Some lenses have stabilization that helps keep that double focal length thing less drastic.


I just ordered this lens, Canon EF-S 10-18mm f/4.5-5.6 IS ST M due for delivery tomorrow, it has image stabilisation. Something else to learn and play with.



jcdeboever said:


> Of course you should really find out the threshold of what you deem acceptable as far as noise level. For example, I find my Fujifilm cameras acceptable up to ISO 6400.


All this will come with practice I think, to be honest I am new to all this, learning from scratch, this image was only the second one I have taken. I realise somethings are not what I would do in a proper photograph, it was just grab the camera on a dark, wet, horrible day, pick something up (the bonsai tree) take it into the conservatory, lightest room in the property, even though the black clouds were getting thicker by the minute and just aim to test what I learned regarding DoF.

Thank you for your help, suggestions and comments they are always appreciated.


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## PJcam (Jan 16, 2018)

Ysarex said:


> Practice practice -- very good for you.
> 
> A couple comments: The software you used to extract the JPEG did not convert the raw file. It simply extracted the embedded JPEG which was in fact created by the camera. All digital cameras create a JPEG whether you want one or not and whether you set the camera to save one or not. A copy of that JPEG is embedded into the raw file and used to preview the raw file.



Thank you for confirming this for me.



Ysarex said:


> Good job with the DOF exercise. As a DOF exercise the photo is fine.



Thank you Joe, that is really all the exercise was, to make sure I understood how to control DoF. I think controlling DoF is just as important as all the other settings, it cn contribute to make or break a final image.



Ysarex said:


> If you want to consider the photo otherwise then I would suggest your background choice for the bonsai tree is poor and that the tree needs to be lit differently. Thinking in very basic terms we (humans) are drawn to light -- makes sense. We preferentially see light and bright objects and concentrate our interest on those over dark objects. That natural trait makes photographing dark objects against light backgrounds typically unsuccessful. You took a photo of the tree, but when I first look at the photo it takes me too long to make the subject recognition. Not only is the background light compared to the tree it's also very graphic which further demands attention. Re-photograph the tree, get some light on it and find a less graphic and darker background.
> 
> Joe



A lot of what you say here I did expect to be honest, my only aim with this experiment was the testing DoF, first I shot 7 images, changing each of the triangle settings, the lowest number F-Stop was the best, this was compared when comparing the images, so my next trial was to use Av, set the F-Stop and change shutter speed and ISO, the image included was the best one. I realise the background could have been better, I wished the light was better but the storm was overhead so I though just try it and include these things to compare DoF, in front of the bonsai and between the blinds and through the glass. To many things and to lighter colours behind, all point to note, but DoF worked enough to confirm what was in my mind was right and I can look to create another image.

Being a 'total beginner' you may find I will share images that are not up to standard, you will LOL, but at this stage of learning I will be testing myself with little projects, possibly shooting anything to try out some of the settings and compare them against each other. I do not take any replies as criticism as they are all supplied to help beginners learn better and hopefully faster.

Many thanks for your comments Joe.


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## PJcam (Jan 16, 2018)

Ysarex said:


> Your chart raises a few red flags. You watched the toothpaste video and you're showing possible influences from the Triangle Cult.
> 
> Toothpaste: The toothpaste video isn't too bad but it doesn't simplify DOF; if anything it complicates it and confuses some important aspects.
> 
> ...



Well Joe, what can I say, we go from red flags, to Triangle Cults, to Circles of confusion and then include noise. I am glad you didn't put those in capitals. (Just joking).

I can see a little in what you say, but being a total beginner I need to hang on to what I learnt so far and put that into practice, practice, practice, before going deeper. That said I am always open to comments, that was why I posted the image, and even if I am maybe not ready for the extra depth of understanding yet, other readers may be. 

For me at this stage, I have proved to myself and had it confirmed on here that as far as DoF is concerned in the image, which is all the test was for from my prospective, I have grasped the basics of controlling DoF. I now need to find other items and do things differently, probably testing other things, the more I learn by using the shutter speeds, aperture and ISO, one against the other the sooner I will get it to gel in the brain and then will become second nature, allowing the mind to concentrate on the items and light in the image, which way they come from, etc, etc.  Sadly until the better weather I cannot get out, I cannot even hobble to the car when the wind is 20mph or more and at present gusts in the mid 60's are forecast. There is a nature reserve within 10 miles, I know my lens are not powerful enough for many of the birds at distance but it will be worth a visit when the weather gets better, there is plenty more items to shoot at not just the wildlife.


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## Designer (Jan 16, 2018)

PJcam said:


> I can see a little in what you say, but being a total beginner I need to hang on to what I learnt so far and put that into practice, practice, practice, before going deeper. That said I am always open to comments, that was why I posted the image, and even if I am maybe not ready for the extra depth of understanding yet, other readers may be.


As a simple observation, it seems to me that you're making this way too complicated.  I know you wrote that we each need to learn how we do it best, but learning DOF by experimentation seems the long hard way as compared with consulting a chart or website.  

You learn your way, and I'll learn my way, but learning DOF wasn't exactly difficult for me, so I just accept it for what it is and move on.


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## TCampbell (Jan 16, 2018)

Ysarex said:


> Your chart raises a few red flags. You watched the toothpaste video and you're showing possible influences from the Triangle Cult. Triangle Cult first: ISO does not control noise in a photograph and increasing ISO does not increase noise. Increasing ISO (especially since you're using a Canon camera) reduces noise. The triangulars are confused about cause and effect. They've attached themselves to a spurious correlation and converted that over to a cause - effect. Noise in a photograph is primarily a function of exposure. Less exposure = more noise and more exposure = less noise. ISO is related: When we don't have enough light to, as JC noted, achieve a fast enough shutter speed then we have to reduce exposure. If we don't have enough light to achieve the aperture we require for DOF then we have to reduce exposure. The noise is a result of reduced exposure. ISO does two things. It biases our camera meter to allow the reduced exposure calculation and then it post processes the sensor capture and brightens the image to compensate for the reduced exposure. In this post processing function ISO typically reduces the noise caused by the underexposure. It may sound like a subtle distinction but it's important to keep cause and effect straight. You can't control noise in a photo with the ISO setting; you have to do that with exposure. Noise is a function of exposure.
> 
> Joe



Joe,

I'm wondering if I've misunderstood what you meant to write.

Noise is a tricky subject to tackle and I honestly don't know anyone who feels completely comfortable tackling all aspects of it.  One of the reasons is that noise is caused by lots of contributing factors... not just one thing.  

Noise is more noticeable as a result of amplification ... which is the gain applied as a result of dialing up the ISO setting.  (Changing ISO does not alter the sensitivity of the sensor.)   This gain (amplification) is either applied via analog means prior to analog to digital conversion (ADC) and is sometimes called "upstream gain", or it could be applied via digital multiplication after ADC and is sometimes called "downstream gain", or a combination of both.  How it's performed varies by camera manufacturer and model.

But noise is caused by lots of other factors... heat build up (which does tend to increase in long exposure images), even quantum effects (that we can't control).  One type of noise is "read noise" and this is an amount of noise inherent in a sensor (due to electronics) and that amount of noise is considered to be fixed. 

We regard an image as "not noisy" not because there is no noise... but because we don't notice it.  This is a result of the "signal to noise ratio" (SNR).  So if "read noise" is fixed... but I can get more "signal" by taking a longer image, then it stands to reason that I will have a better SNR by taking a longer exposure image than a shorter exposure image.  This supports the hypothesis that a longer exposure duration should result in less noise (which is what I believe you are saying).  But this is primarily a function of read noise.  But there are other types of noise.  

This is why I started with "I don't know anyone who feels completely comfortable tackling all aspects" of noise.

I can say that as an astrophotographer (where shooting really long exposures at high ISO is pretty common)... it doesn't matter that I can take a really long exposure.  We still get more noise at higher ISO levels (regardless of exposure duration).  (Astrophotographers deal with this by taking loads of images of the same object and then using "stacking" software to integrate the images ... especially using statistical integration algorithms which do a pretty impressive job of knocking down the noise.)

If the hypothesis that noise is primarily just a function of exposure duration, then we should be able to predict that if, in addition to increasing ISO, we also increase the exposure time, then we should not see an increase in noise because we've maintained the exposure duration.

So for example:

ISO 100 at f/2.8 for 30 seconds   ... compared to ...   ISO 12,800 at f/32 for 30 seconds 
(trading 7 stops of aperture for 7 stops of ISO so we can maintain the same 30 second exposure duration).

But if I do this test... I get no _noticeable_ noise in the ISO 100 image, but loads of noise in the ISO 12,800 image.  

The data does not support the hypothesis that noise follows exposure time (instead of ISO).  

I could also shoot at ISO 12,800 but trade 7 stops of aperture for exposure duration (so f/2.8 at 1/4 seconds instead of f/32 at 30 seconds).  This also results in a noisy image.  There may technically be less total noise in the longer exposure due to the improved SNR ratio w.r.t. the "read noise" component of the total noise, but because this is being overwhelmed by other contributors to noise, I don't notice an obvious improvement to the image.  The only way I do notice a dramatic and obvious difference, is to lower the ISO value.

In testing that I've done... noise primarily follows ISO setting (at least with my cameras).  I have specifically tested the scenario where I set a low ISO with a long image duration (30 seconds) to get a representative sample of how much noise I get.  Then used a very high ISO but still use the same 30 second exposure time (compensating by stopping down aperture) and can confirm that the long exposure does not help smooth out the noise problem in any meaningful way.  The only way to get a meaningful reduction in noise from a single image is to use a lower ISO value.

There are loads of contributing factors to noise.  And one major wrench-in-the-works is that accurately assessing a sensor relies on having information available which manufacturers do not share.  We do (now) know that many manufacturers "cook" their RAW images (in other words the true read noise & shot noise is higher than they let on... but they de-noise the images ... and still tell us these "cooked" images are "RAW") and this makes it difficult to accurately assess the camera at a technical level.

In science, if we observe a behavior and try to ascribe a cause, we might be able to do that if there is _only_ one cause.  If there are multiple causes, it is difficult to understand how much of the observed behavior should be ascribed to one factor vs. another factor.  If we can gain confidence that we thoroughly understand one of those factors, then we can more accurately understand the _other_ factor (because it's responsible for whatever is left over).  But if you have multiple factors (more than two) ... especially when you don't know how many factors you're dealing with (and some of it's trade-secret) it gets really hard to be able to say we understand or can accurately explain the observed behavior.

So I wont attempt to say "why" noise follows ISO (more than exposure duration).  I can only state that testing the camera shows that it does.

Tim


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## Ysarex (Jan 16, 2018)

TCampbell said:


> Ysarex said:
> 
> 
> > Your chart raises a few red flags. You watched the toothpaste video and you're showing possible influences from the Triangle Cult. Triangle Cult first: ISO does not control noise in a photograph and increasing ISO does not increase noise. Increasing ISO (especially since you're using a Canon camera) reduces noise. The triangulars are confused about cause and effect. They've attached themselves to a spurious correlation and converted that over to a cause - effect. Noise in a photograph is primarily a function of exposure. Less exposure = more noise and more exposure = less noise. ISO is related: When we don't have enough light to, as JC noted, achieve a fast enough shutter speed then we have to reduce exposure. If we don't have enough light to achieve the aperture we require for DOF then we have to reduce exposure. The noise is a result of reduced exposure. ISO does two things. It biases our camera meter to allow the reduced exposure calculation and then it post processes the sensor capture and brightens the image to compensate for the reduced exposure. In this post processing function ISO typically reduces the noise caused by the underexposure. It may sound like a subtle distinction but it's important to keep cause and effect straight. You can't control noise in a photo with the ISO setting; you have to do that with exposure. Noise is a function of exposure.
> ...



I never suggested noise follows exposure time. Noise follows exposure. In your example the second shot taken at f/32 is exposed massively less than the first shot taken at f/2.8. And that's the cause of the noise. Exposure = quantity of light per unit area reaching the sensor: function of ambient light level + time + attenuation through the lens (f/stop).



TCampbell said:


> I could also shoot at ISO 12,800 but trade 7 stops of aperture for exposure duration (so f/2.8 at 1/4 seconds instead of f/32 at 30 seconds).  This also results in a noisy image.  There may technically be less total noise in the longer exposure due to the improved SNR ratio w.r.t. the "read noise" component of the total noise, but because this is being overwhelmed by other contributors to noise, I don't notice an obvious improvement to the image.  The only way I do notice a dramatic and obvious difference, is to lower the ISO value.
> 
> In testing that I've done... noise primarily follows ISO setting (at least with my cameras).  I have specifically tested the scenario where I set a low ISO with a long image duration (30 seconds) to get a representative sample of how much noise I get.  Then used a very high ISO but still use the same 30 second exposure time (compensating by stopping down aperture) and can confirm that the long exposure does not help smooth out the noise problem in any meaningful way.  The only way to get a meaningful reduction in noise from a single image is to use a lower ISO value.
> 
> ...



Most of us are not astrophotographers and the noise due to heat from long exposures isn't an issue for the overwhelming majority of photos taken - like +99% of them. We can set that aside as special case.

That leaves us with the two primary sources of noise: shot noise and read noise. Given today's modern sensors, read noise is reaching the point of negligibility compared with shot noise (think ISO invariance). When people today notice noise in their photos they're basically seeing shot noise. And the cause of that noise is reduced exposure -- failing to fully expose the sensor.

I simplified based on what people in fact are really experiencing.

The ISO brightening applied as either analog gain or digital scaling or both amplifies the noise along with the rest of the signal but, the critical point: *it is not the cause of the noise. The cause is failing to adequately exposure the sensor.*

Given the colloquial presentation of exposure controls and ISO there's a tendency to attribute causation for noise to ISO. Yes, they're linked via exposure. When folks raise the ISO value on a camera they're typically doing that to calculate an exposure reduction. Then they get a noisy photo and say ISO caused the noise. *No, the exposure reduction caused the noise.*

In cameras (most cameras) where analog gain is used as the method of ISO brightening the applied gain improves the result due to read noise and so applied ISO brightening in most cameras helps suppress noise.

Joe


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## TCampbell (Jan 16, 2018)

Ysarex said:


> I never suggested noise follows exposure time. Noise follows exposure. In your example the second shot taken at f/32 is exposed massively less than the first shot taken at f/2.8. And that's the cause of the noise. Exposure = quantity of light per unit area reaching the sensor: function of ambient light level + time + attenuation through the lens (f/stop).
> 
> Joe



Ahhh... that makes MUCH more sense.  And yes, I agree.

I had previously thought you were linking it to exposure duration.  

Another way of thinking about this:  It's somewhat common to read that "ISO changes the camera's sensitivity to light".  ISO doesn't actually change the sensitivity ... the chip is as sensitive as it is.  However much light was captured during the exposure (based strictly on aperture and shutter time and ignoring ISO) is whatever it is.  Boosting ISO is simply applying amplification to whatever came in... after the fact.

It's a bit like radio.  If the radio station is close and the signal is strong, you get a nice clear signal.  If the radio station is distant and the signal is weak, you might hear a lot of static.  You could "amplify" the weak signal to make it louder, but that amplifies _everything_ (both the signal you want to hear... and the noise & static you don't want to hear ... it all gets louder).  

If you can use an exposure that adequately captures the shot _without_ boosting ISO, then that would be a much cleaner image.


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## Ysarex (Jan 16, 2018)

PJcam said:


> Ysarex said:
> 
> 
> > Your chart raises a few red flags. You watched the toothpaste video and you're showing possible influences from the Triangle Cult.
> ...



Apologies --  I tend to over do it at times.

In terms of DOF this may be still helpful and new info: The change in DOF when you change from one f/stop to the next is approx. 50%. The change in DOF when you change magnification by a factor of 2 is a factor of 4. In other words move a camera closer from 6 meters to 3 meters (factor 2) and the magnification will double while the DOF zone will shrink to 25% of its previous depth. Same thing works with focal length. Take a photo from 6 meters with a 50mm lens. Switch to a 100mm lens and the magnification will double while the DOF zone will shrink to 25% of its previous depth. Works in reverse the same way. What you then discover is that magnification has a greater effect on DOF than does f/stop.

Joe


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## jcdeboever (Jan 16, 2018)

As promised


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## Ysarex (Jan 16, 2018)

TCampbell said:


> Ysarex said:
> 
> 
> > I never suggested noise follows exposure time. Noise follows exposure. In your example the second shot taken at f/32 is exposed massively less than the first shot taken at f/2.8. And that's the cause of the noise. Exposure = quantity of light per unit area reaching the sensor: function of ambient light level + time + attenuation through the lens (f/stop).
> ...



Yeah, Don Quixote here. When I fully retire I can ignore the windmills but for now this continues to plague me. I'm starting a new semester now and here I go again. Every semester I get students in class I have to deprogram from the Triangle Cult. They get sucked in on Youtube before I get them. You're immune but, take an impressionable beginner and before you know it they believe ISO is an exposure determinant. Youtube tells them that each of the three vertices of the triangle balance against the other two. Therefore:
1/500 sec, f/8 and ISO 200
1/125 sec, f/16 and ISO 200
1/500 sec, f/11 and ISO 400
all balance as equivalent exposures. And ISO causes noise. PITA, so when I see a beginner here at TPF I sometimes try and save them before they get sucked in.

Joe



TCampbell said:


> It's a bit like radio.  If the radio station is close and the signal is strong, you get a nice clear signal.  If the radio station is distant and the signal is weak, you might hear a lot of static.  You could "amplify" the weak signal to make it louder, but that amplifies _everything_ (both the signal you want to hear... and the noise & static you don't want to hear ... it all gets louder).
> 
> If you can use an exposure that adequately captures the shot _without_ boosting ISO, then that would be a much cleaner image.


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## PJcam (Jan 17, 2018)

Designer said:


> PJcam said:
> 
> 
> > I can see a little in what you say, but being a total beginner I need to hang on to what I learnt so far and put that into practice, practice, practice, before going deeper. That said I am always open to comments, that was why I posted the image, and even if I am maybe not ready for the extra depth of understanding yet, other readers may be.
> ...



No problem Designer, we are also all at different stages. For me, I have a camera and a couple of lens, purchased as a bundle, I know where the shutter button is and the lenses go on the front, I still haven't found out where to put the film!  That puts where I am in prospective, I have had the camera 2 weeks, I have one foot on the learning ladder it is only on the first step.

Instead of getting to know how Shutter speed, Aperture and ISO work or how they need to be set to work together, I stepped ahead, I wanted to understand DoF, for me it just seems an important part of some or many finished pictures. So I did what made sense at the time, try in and see, practice and learn, I also did what the forum suggests, go on share your image, don't be shy. The forum encourages us all, no matter how much or how little we know, or don't now, to share and ask questions.

I honestly cannot wait for the better weather to be able to get out and experiment outdoors. Now where does that damn film go.


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## PJcam (Jan 17, 2018)

Interesting discussion guys, but in some ways I cannot help but think, over 90% of people would not be concerned to the level of thought here, but are more concerned with reducing noise (or using) noise to get the best from their shot.

My next thought, as a total beginner, is although there are several (more than two) items influencing noise in the image, probably one of them is a bigger influence than the others. @TCampbell uses the word, 'amplified' this one seems to me, at this stage of understanding, to be a better description of the issue relating to noise.

I watched this YouTube video the other day regarding ISO and noise...





The explanation in the video made sense and shows clearly that amplification is a big part of the issue. (We have accepted there is more than one reason).

'Amplification' as shown in the video is relating to and causes noise, or increase noise, amplifies the noise. I am thinking maybe it is a little bit like taking a medium resolution image and altering it's size to make the image larger, doubling it's size, as a result we amplifying any noise already in the image so the quality of the image deteriorates. 

I this wrong thinking?


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## jcdeboever (Jan 17, 2018)

Keep it simple. ISO is a tool to gain shutter speed. 

The above lesson and guide makes it real simple to understand DOF, that's what I love about John Hedgecoe books, simple with lots of pics. @Derrel recommended them to me about 2 years ago when I was first starting out. They're old but still apply. I paid like a $1 for almost everyone I own. I have literally done over 100 projects contained within them. It got me out shooting and associating with the text to expedite learning.


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## Designer (Jan 17, 2018)

PJcam said:


> [/MEDIA]
> 
> The explanation in the video made sense and shows clearly that amplification is a big part of the issue. (We have accepted there is more than one reason).
> 
> ...


Wrong?  I say more like mislead.  

There are probably several videos available that purport to teach the technology of digital photography, and the problem is to figure out which ones are correct.  

I started the video you referenced, and noticed that he made a fundamental mistake at only 18 seconds into the video.  The sensitivity of your sensor doesn't actually change.  It is what it is from the day of manufacture until it is finally scrapped and sent to the Great Recycling Bin in the sky.  Stays the same.  Does not change.

As @TCampbell wrote; ISO is applied gain.  That kind of makes it a requirement that the data has already been collected.  (exposure made, file saved)  Then what part does the ISO setting play?  Deep within the electronic components of your image processor (the camera) the electrons get to work and produce a viewable (to human eyes) image and display that image on the LCD.  

The short version:

1. Some cameras handle applied gain better than others.  

2. Some exposures test the hardware and firmware to a practical limit (underexposures or exposures in low light conditions).  

If those factors are put to their limits, then you see artifacts of electronic noise.


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## Ysarex (Jan 17, 2018)

PJcam said:


> Interesting discussion guys, but in some ways I cannot help but think, over 90% of people would not be concerned to the level of thought here, but are more concerned with reducing noise (or using) noise to get the best from their shot.



Absolutely and I think it's fine if most people just black box it and learn to use it to get repeatable results. I can even just stand there and smile when I hear someone say ISO adjusts the light sensitivity of your camera. Bleepin bleep Nikon even says that on their web page (don't read that!)-- talk about misinformation!

But I can't let a room full of photography students keep functioning that way. And I do see that the misunderstanding has real ramifications that show in their photos -- their confusion causes them to reach wrong conclusions and do the wrong thing. So OK I'm letting my other life spill over in The Photo Forum -- sorry there.

As a related aside to this I recently had to create an test example of my Fuji X-T2 used at ISO 25K -- that's an APS class sensor used with the ISO set to 25,600. I went down in the basement (very dark) and took a photo of my canning shelf. Must be gosh awful noisy: green beans



PJcam said:


> My next thought, as a total beginner, is although there are several (more than two) items influencing noise in the image, probably one of them is a bigger influence than the others. @TCampbell uses the word, 'amplified' this one seems to me, at this stage of understanding, to be a better description of the issue relating to noise.
> 
> I watched this YouTube video the other day regarding ISO and noise...
> 
> ...



Your analogy of enlarging a lower res image isn't bad but that video is very bad and very wrong. The Internet has effectively reduced the cost to publish to $0. The old method of publishing on paper wasn't fool proof but at least someone at some level who had to open their wallet and pay to run the press was entitled to ask the question, "what is it were publishing and is it worthwhile and has someone checked it over for mistakes?"

Amplification? yes and no. We have a case here of finding the right words to fit what's going on -- I like boost. As usual it tends to be a bit more complicated. One method employed in our cameras is analog signal amplification -- the electrical signal (photons to electrons) is boosted through an amplifier. The word amplification has connotations that don't entirely match up and more and more in our modern cameras, because the *only source of noise that the video identifies is no longer a factor*, we're foregoing the analog amp stage and replacing it with the much less expensive digital scaling (strictly numbers) stage and/or combining the two methods. There's no analog amp in the Nikon D7000 so it's tricky to say that the signal is amplified. My old X-E2 combined both methods.

The noise we see in our images today isn't coming from the camera circuitry (heads up Youtube). We've effectively beaten that down. Those were the good old days. The noise we see now in our photos is the noise contained in the signal itself. A weak signal is noisy and that's what is causing noise in our photos. That's why I said noise is exposure (and ISO does not determine exposure). Here's another fun fact: Digital camera sensors don't have assigned ISO values. The ISO values on your camera do not refer to the sensor in your camera -- not even the base ISO value. They reference the output from the camera's JPEG processor.

Joe


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## Braineack (Jan 17, 2018)

Ysarex said:


> The noise we see in our images today isn't coming from the camera circuitry ... The noise we see now in our photos is the noise contained in the signal itself.



how is the signal generated if not from an electrical circuit?


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## Ysarex (Jan 17, 2018)

Braineack said:


> Ysarex said:
> 
> 
> > The noise we see in our images today isn't coming from the camera circuitry ... The noise we see now in our photos is the noise contained in the signal itself.
> ...



Thanks -- precise language is always hard. Shot noise is in the incoming signal (photons) that reach the sensor -- the light. It's not added to signal leaving the sensor (electrons) by the circuitry. Read noise is noise from the circuitry and has been a real problem in earlier cameras. It's still there but it's suppressed now to a level where it's nominal and not the noise that we see in our low-light photos with modern cameras.

Joe

Here's a reference: What's that noise? Part one: Shedding some light on the sources of noise


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## Braineack (Jan 17, 2018)

that's pretty much what the video suggests...


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## Ysarex (Jan 17, 2018)

Braineack said:


> that's pretty much what the video suggests...



The video doesn't mention or suggest shot noise at all. And so viewers are likely to draw the wrong conclusion as to the noise source. What's that noise? Part one: Shedding some light on the sources of noise

Joe

P.S. Went back and looked at the video more carefully and in fact he's confused. He talks about the noise be amped up along with the signal when ISO gain is applied. That's what happens to shot noise and upstream read noise, but the noise he describes as caused by the electronic circuitry is in fact downstream read noise which is not amped up along with the signal but applied after ISO gain.


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## PJcam (Jan 17, 2018)

Ermmmm. I think, if I keep ISO as low as possible, get best shot I can, learn from it and constantly look to improve, I am probably on the right track. The key being I cannot get a good image from a bad one (as the example previously discussed) so get the best shot(sssss) I can. 

Got to go I have a lot to learn.


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## Ysarex (Jan 17, 2018)

PJcam said:


> Ermmmm. I think, if I keep ISO as low as possible, get best shot I can, learn from it and constantly look to improve, I am probably on the right track.



Errrrrrrr no. That's one of the faulty ideas my students show up with. They think raising ISO is the source of noise. They don't like noise and so they say to themselves "keep ISO as low as possible." They've also been screwed up by this idea that they can't be real photographers unless they use their camera's in full manual. The scenario: They want to take a photo in low light. Camera ISO is set to 200. They check the meter and discover they need a shutter speed of 1/8 sec. They know they have to raise ISO but that causes noise and so they resist. They figure they need to get the shutter up to 1/125 sec. but that forces the ISO to 3200. That's too high so they settle on a shutter speed of 1/100 sec and set the ISO to 1600 thinking they're close enough and they're holding the noise down. Using the camera in manual they can do that. They get a noisier photo having made matters worse. What they should have done was try the 1/100 sec. if they thought they could manage that but then set the ISO to 3200 or even higher at say 5000. In this case raising the ISO will reduce noise. Bottom line: the noise is coming from the exposure. The correct thinking is keep the exposure as high as possible but then raise the ISO as needed. Take a hard look at that photo I posted above of canning shelves. ISO is 25,600.

Joe



PJcam said:


> The key being I cannot get a good image from a bad one (as the example previously discussed) so get the best shot(sssss) I can.
> 
> Got to go I have a lot to learn.


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## Designer (Jan 17, 2018)

PJcam said:


> Ermmmm. I think, if I keep ISO as low as possible, get best shot I can, learn from it and constantly look to improve, I am probably on the right track.


Now you're not just misinformed, you're also wrong because of it. 

The people who tell you to keep the ISO as low as possible are wrong.  Yes, I know that is about 90% of what you see on the internet, so you're going to have to start ignoring that information.  

If you haven't already, have a look at Joe's low-light high-ISO photograph.  

So now, you are probably wondering what to do with all that ISO stuff.  Fair question.  

I say for most photography, set your ISO to "auto" without any limit high or low.  No need to fiddle with the ISO setting.


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## TCampbell (Jan 17, 2018)

Designer said:


> PJcam said:
> 
> 
> > Ermmmm. I think, if I keep ISO as low as possible, get best shot I can, learn from it and constantly look to improve, I am probably on the right track.
> ...



As a broad generalization... you DO want to keep ISO low.  But things get subjective at some point because what does "as low as possible" really mean?

"As low as possible" could be interpreted to just mean use ISO 100 all the time.   But that's probably not realistic.  I mean there's nothing stopping you from doing that... but you probably wont be happy with many of your pictures.

Camera lenses each have a finite number of aperture stops possible.  

Suppose I meter a shot and determine that at ISO 100, that f/2.8 and 1/60th second would be a good exposure.

If the lowest aperture possible with the lens is f/4 then you can't shoot at f/2.8 -- the camera wont offer you that choice.  To compensate, I could just keep the shutter open for twice as long.  But suppose I'm hand-holding the camera (and we'll ignore image-stabilization features of lenses) and the slowest shutter speed I think I can safely manage given my lens focal length might be 1/60th sec.   

If we keep the ISO at 100 then my f/4 lens limits my choices and the only thing left is to change the shutter speed to 1/30th sec.  But the problem is... I can't hold the camera steady enough to get a clean shot at 1/30th sec.   I could take it at 1/30th anyway and risk having motion blur (and that's pretty much a lost shot because there isn't much you can do to clean up motion blur).

OR... I could cave on the ISO and raise it to 200... now I can use f/4 and 1/60th and get a clean shot.  Honestly... ISO 200 is probably going to look just as good as ISO 100 to most people and with most cameras.  But there are limits to how far you can go before you start to notice the noise.

The thing is... we can't do much about the blur in post processing... but we can actually do something about the noise.  Modern de-noising software is pretty good about cleaning it up.  So given a choice between a blurry shot and a noisy shot, I'll take the noisy shot.

That's an example where refusing to raise the ISO would be detrimental.  But what about using high ISOs?

Lets take a radically different approach... I should be able to crank that shutter speed up to 1/2000th sec (so now I definitely don't have motion blur from camera movement).  From 1/30th sec... that's 7 stops up.    So I crank the shutter up AND I crank the ISO up 7 stops to "compensate" and now I've got ISO 12800.  

The problem with this is... you ARE going to see some noise at ISO 12800 (with any camera).  

Before you say "But look at Joe's image"... I give you this:  Elevating X-Trans? Fujifilm X-T2 Review
Flip the setting to RAW mode, crank it to 25600 (Joe's camera... Joe's ISO setting) and... you have noise (loads of noise).  Of course you can flip it back to JPEG mode and much of the noise goes away... at the expense of some loss of detail.

If you value dynamic range, then there are technical reasons to avoid high ISOs.  Increases to ISO result in decreases to dynamic range.

I do not (and I hope neither does anyone else on TPF) advocate that you just go out and crank up the ISO because you can and it's an equally valid exposure.  Your shots wont look as good if you do that and I certainly hope it wasn't the intention of anyone here at TPF to mislead someone into that way of thinking.

Middle ground

All cameras look great at ISO 100.  Most probably look great at ISO 800.  Better cameras look great at ISO 1600.  Some of the best cameras still look great at ISO 3200.  But there is some point with every camera where you finally decide that you're no longer happy with the amount of noise.  

I'll flip between low-ish ISO values without giving it too much thought.  I wouldn't say you must use the lowest _possible_ ISO.  But I would use the lowest _reasonable_ ISO.   Even with ISO values that result in noise... there are ways to clean up noise.  

You don't need to live in fear of raising the ISO above 100... but you should give consideration to your exposure and keep the ISO low when practical.


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## Ysarex (Jan 17, 2018)

TCampbell said:


> Designer said:
> 
> 
> > PJcam said:
> ...



No one was suggesting any such thing. The goal (at least mine) is to help break the thinking that raising ISO causes noise. It doesn't. What ISO does in a camera does not directly cause noise. Raising ISO biases the camera meter to reduce exposure and it's related to noise in that reducing exposure causes noise. The critical point is that the noise is coming from the reduced exposure. What ISO does as the image is processed in fact helps suppress noise and so the user shouldn't fear raising the ISO if indeed the circumstances warrant it. Sometimes the circumstances warrant it.

As for the methodology of setting a camera to auto ISO and letting the camera select it -- that can be a really effective way to work. The camera's programming works to keep the ISO as low as possible and if you want to remove the option from the camera of possibly selecting a compromise just put the shutter & f/stop to full manual -- the camera software won't have a choice then over the ISO.

If you're concerned about noise and loss of DR in a photo then you should think about maximizing exposure. Thinking directly about the cause and effect factors has an advantage over thinking about it circuitously through ISO -- especially for beginners who are more likely to get confused.

NEXT topic: My photo and DPR's testing. I never shoot camera JPEGs and that photo was processed from a raw file. Yes of course it was noise filtered. So six - seven stops of underexposure -- I can do that with my camera now photographing "normal" scenes and processing a raw file to a usable result without appreciable noise. Add a touch of simulated grain which looks good and it masks the noise and you'd be hard pressed to see it. Here's seven stops -- camera ISO set to 12K processed from raw: CDs and film Compare that to the test file at DPR for an X-T2 and I make their result look pitiful. You can download their raw file. I did and I examined it in RawDigger. *It's nearly a full stop underexposed for ISO 12K!! No wonder it looks like bleep. *I didn't do that with my photo and I have a much less noisy photo than they do -- noise is caused by underexposure. Stops are exponential. Think about how much more exposure I got than they got. If you're trying to avoid noise in your photos the biggest mistake you can make is to further underexpose after you've already underexposed for the ISO increase. That's like getting down on your knees and begging for it.

Joe



TCampbell said:


> Middle ground
> 
> All cameras look great at ISO 100.  Most probably look great at ISO 800.  Better cameras look great at ISO 1600.  Some of the best cameras still look great at ISO 3200.  But there is some point with every camera where you finally decide that you're no longer happy with the amount of noise.
> 
> ...


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## PJcam (Jan 18, 2018)

How easy it is to try describe something then realise one word, or a couple, can cause the message to read differently to that initially intended.

When I stated to keep ISO as low as possible, it didn't mean to set at it's lowest value, 100, when I said as low as possible what I really meant, or should have said, was as low as possible based on the metered values the camera provides. Therefore is the metered values for ISO are say 1600, then I should also consider using ISO 800, and it would be worth also trying ISO 1600. But the priority would be keeping ISO as low as possible (based on the metered values). Thanks for the comment and details you have provided Tim.



TCampbell said:


> As a broad generalization... you DO want to keep ISO low. But things get subjective at some point because what does "as low as possible" really mean?
> 
> "As low as possible" could be interpreted to just mean use ISO 100 all the time. But that's probably not realistic. I mean there's nothing stopping you from doing that... but you probably wont be happy with many of your pictures.



Please accept my comments as a new student, what I know, (which is not a lot) I have learned in two weeks, which is not enough time to absorb much at all, so any replies or comments I post, with best intentions, can only be based on considering what I know and what has been stated in reply.



Ysarex said:


> As for the methodology of setting a camera to auto ISO and letting the camera select it -- that can be a really effective way to work. The camera's programming works to keep the ISO as low as possible and if you want to remove the option from the camera of possibly selecting a compromise just put the shutter & f/stop to full manual -- the camera software won't have a choice then over the ISO.



The position I am at at present says to me that, there does appear to be more than one reason for Noise in a shot. I understand what you say Joe about trying to get people to break free from the Triangle Rule and ISO/Noise, but not as an alternative way of thinking but an additional way of thinking, after all there is more than one reason noise is evident in an image.

I say to myself, my camera is a mini computer, a very clever mini computer, but in the end that is what is is, a mini computer for capturing images and processing them. I then read your comment Joe, '_The camera's programming works to keep the ISO as low as possible ',_ the software in the chip or chips in the camera are... programming to keep ISO as low as possible. So this is saying to me, the manufacturers of cameras, more than one, are programming the cameras the same way, to keep ISO as low as possible. 

So listening to the comments mentioned so far, I am thinking, as stated yesterday, I should keep ISO as low as possible, but at the same time, as stated in this message above, as low as possible based on the cameras metering for my shot. Therefore with keeping metering in my mine when taking shots, I should also consider the camera is 'programmed to do this' so I should also consider maybe one stop more than the camera suggested when it metered the shot, e.g. camera suggests ISO 1600, although I may consider ISO 800, or lower, there is nothing wrong with also considering ISO 3200.

I appreciate this post started as a test for DoF, and has changed considerably to ISO and Noise, but I do not see it as a problem as it was only a general test of DoF and the conversation has been mainly ISO and Noise. Maybe the title should be changed to A Test for DoF -  ISO and Noise.I don't know how to or if I can change a title to a post.


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## vintagesnaps (Jan 18, 2018)

These threads do tend to go a bit off track! lol It might be worth coming back and rereading it later on, then it might all make more sense. I think it can be a good way to learn by setting up your own shots and experimenting; sometimes what doesn't work can help you figure out what else will work.

I did get a laugh out of Joe's triangulators, or was it triangulars? I don't quite think the triangle is the best way to understand how aperture, shutter speed, and ISO work together. But it's all over the internet... I think there are a lot of places (blogs, Youtube, etc.) where people can put info. out there without necessarily having much expertise, and people learning photography might do better if they could unlearn some of what they learned online. I think what you're talking about is using the lowest ISO needed, rather than setting it higher than necessary. I'm a longtime film photographer and on occasion used higher speed film like 800 or 1000 ISO but never really liked them; the color and quality wasn't as good. Maybe that's along the same lines, I use 100 outdoors and 400 low light or indoors, etc. I don't get the best result using a higher light sensitivity than necessary, shooting film or digitally.

In the photo you posted, I think facing toward a window the meter could have been reading the light behind the subject. Sometimes I aim the camera downward to meter, then reframe. I'd consider backgrounds too, since even if it's out of focus there can be bright colors that can still be visually distracting. Also with your photo, you mentioned the tilt. I think that can work, but with this I wasn't sure if it was framed at a tilt or was just not quite straight. You might be interested in looking at a technique called 'canted' or 'Dutch' angle. (I think it being called Dutch was an inaccurate variation of Deutsch, because it was seen in German expressionist films.) It was used in movies like 'The Third Man', and I like the clip from the film 'The Conformist'; I like the way the car keeps following the guy, and the tilt just throws you more off balance about what is going on.
Columbia Film Language Glossary: Canted Angle (Dutch Angle)
The Third Man | Gene Siskel Film Center





Someone, I think maybe it was JC, mentioned Hedgecoe; I either have/have read the same book or something else by him. Or 'The Photographer's Eye' by john Szarkowski was good (not the book of the same name by Freeman, I wonder if people get them mixed up).


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