# Digital Photography ISO



## VidThreeNorth

This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.

*"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler


----------



## jcdeboever

Digital ISO is similar to film. It is gain.

When you need to gain shutter speed to meet your requirement. If your subject is stationary and your ISO is 200, your lens focal length is 50mm, happy with aperture setting for depth of field, and your proper exposure calls for 1/125s shutter speed, then your good. Same scenario but your subject is moving and you want to freeze the movement and you know you need at least 1/500s to do so, you will need to increase your ISO 2 stops, 800 ISO in order to gain up to 1/500s for proper exposure.

That's how I look at it. I use it to gain shutter speed for double the focal length of lens when hand holding or when a subject is moving and I want to isolate the subject and movement.


----------



## Ysarex

VidThreeNorth said:


> This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.
> 
> *"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler



Richard Butler can be obtuse at times and hard to understand, but he tends to be accurate.

What camera are you shooting? That will help a lot.

Joe


----------



## snowbear

jcdeboever said:


> Digital ISO is similar to film. It is gain.


or an amplifier - basically the same thing.

Oh, and for the record, ISO refers to the "International Organization for Standards," the acronym actually derived from isos (Greek for "equal").


----------



## VidThreeNorth

jcdeboever said:


> Digital ISO is similar to film. It is gain.
> 
> . . .



Uh, actually, this is what the article is getting at.  No it is NOT necessarily "gain".  It _might_ be gain, but that is not specified.  The only thing specified is that the JPEG output corresponds to certain expectations regarding the camera settings used when taking the picture.  For example, if you look at a "RAW" file, it might simply be parameters set in a file header with no difference at all between the real recorded data from this group of settings and another.
_[2018-08-15 reformatted and clarified -- a bit.]_

. . .



jcdeboever said:


> That's how I look at it. I use it to gain shutter speed for double the focal length of lens when hand holding or when a subject is moving and I want to isolate the subject and movement.



Yup.  That's how I look at it too -- because that is all that I know about what is actually happening.



Ysarex said:


> . . .
> 
> Richard Butler can be obtuse at times and hard to understand, but he tends to be accurate.
> 
> What camera are you shooting? That will help a lot.
> 
> Joe



Hmm.  Good questions.  I guess for the last year I have mainly used the Yi-M1 for stills, though I used a Sony a5000 quite a bit as well, and my Panasonic GF-3, and occasionally, other stuff.  For the coming year, I think I will use the Yi-M1, Sony a5000 and the Olympus OM-D EM10.  Oddly, after suffering through all the early firmware versions of the Yi-M1, the last version 3.1 is actually quite good for my needs.  I think it is one of the best setup for use with adapted manual lenses around.  And they probably released that firmware after the last of the bodies was already sold to an end user.  I think I respect that much of their effort.


----------



## Designer

VidThreeNorth said:


> So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.


No.

Understandable.

Nope. 

ISO in film is related to the sensitivity of the film, however; ISO in digital is actually applied gain.  Sort of like turning up the volume control on a stereo.  Notice; it is applied to the data AFTER the data has already been captured. 

This implies that it has absolutely nothing to do with exposure, which it doesn't.  The purpose of ISO in your firmware is for the camera's display to enable it to produce a viewable image for you to evaluate composition, histogram, and focus. 

Therefore; ignore the "exposure triangle" meme, and consider your exposure to be regulated by your aperture and shutter speed.  You can let the camera select the ISO by setting it to "auto", which should give you a viewable image. 

Variables that affect exposure


----------



## Ysarex

Ysarex said:


> . . .
> 
> Richard Butler can be obtuse at times and hard to understand, but he tends to be accurate.
> 
> What camera are you shooting? That will help a lot.
> 
> Joe





VidThreeNorth said:


> Hmm.  Good questions.  I guess for the last year I have mainly used the Yi-M1 for stills, though I used a Sony a5000 quite a bit as well, and my Panasonic GF-3, and occasionally, other stuff.  For the coming year, I think I will use the Yi-M1, Sony a5000 and the Olympus OM-D EM10.  Oddly, after suffering through all the early firmware versions of the Yi-M1, the last version 3.1 is actually quite good for my needs.  I think it is one of the best setup for use with adapted manual lenses around.  And they probably released that firmware after the last of the bodies was already sold to an end user.  I think I respect that much of their effort.



Shadow Improvement versus ISO setting.

The Sony and Olympus you noted are included in Bill's data base -- no Y1-M1. I added the Canon for comparison so you could see a situation where there's a big difference. Apart from the Olympus jump from base to ISO 400 both the Olympus and Sony tend toward ISO invariance. I believe I read that the Y1-M1 was built on a Sony sensor and so it would likewise tend toward ISO invariance.

Raising ISO reduces dynamic range. Here's that chart: PDR versus ISO for the Sony and Olympus. The Olympus again show a bump between base ISO and ISO 400 that suggests the sensor may have dual impedance channels.

DR dropping with increasing ISO is the opposite of film behavior and so the film analogy is weak. Film DR drops when it is pushed and that's a better analogy to digital ISO. Contrary to popular misunderstanding ISO does not increase the light sensitivity of the sensor. When circumstances require, raising the ISO reduces exposure to the sensor and we're simply left with less recorded data due to less exposure. ISO takes that less data and by one or another or combination of methods brightens it to the level required for a normal brightness photo.

As Richard Butler explains the colloquial understanding of ISO's relationship with noise is fundamentally a misunderstanding. Noise in a photo can result from multiple sources some pretty esoteric like heat build up due to very long exposure. For most of us doing normal photography there are two noise sources in our photos; shot noise and read noise. The dominant noise source in modern cameras is shot noise and that is a function of exposure. Note for example the noise level in this photo taken at ISO 12,800: socks -- I exposed for minimal noise. The noise level is a function of the exposure and not the ISO 12,800 setting on the camera. Shot noise is in the light itself and the better the SNR (more exposure) the less noise and the worse the SNR (less exposure) the more noise.

Read noise comes from the electronics in the camera and in the case of ISO the electronics that boost, gain, amplify, brighten, the sensor signal to the ADC. With each generation of new cameras we reduce or remove read noise from our systems (better engineering). That's what ISO invariance is all about. With todays modern cameras read noise is rapidly becoming a non-issue. Note that in the graph above I referenced an old Canon 5dIII to get a result that wasn't basically pretty flat. With read noise eliminated from our systems ISO can be thought of as only useful to the process of generating a camera JPEG of the required brightness (can't live without chimping!).

Joe


----------



## VidThreeNorth

*@Ysarex:  *Thanks for those links!  I've had a lot of fun playing with the graphing functions.  The Yi-M1 has the same sensor as the Panasonic GH5, and it looks like the same sensor is in the GX9, so I am using them to represent the Yi-M1.

I get the distinct impression that Sony deliberately bypassed an upgrade to their Micro 4:3 sensor lineup.  There has not been a true "back illuminated" Micro 4:3 sensor.  That should have been the natural development step before the APS-C and Full Frame sensors.  Yet magically, Sony was able to come up with APC-C and Full Frame back illuminated sensors (a6500 and the a7iii).  Hmm...


----------



## Ysarex

VidThreeNorth said:


> *@Ysarex:  *Thanks for those links!  I've had a lot of fun playing with the graphing functions.  The Yi-M1 has the same sensor as the Panasonic GH5, and it looks like the same sensor is in the GX9, so I am using them to represent the Yi-M1.
> 
> I get the distinct impression that Sony deliberately bypassed an upgrade to their Micro 4:3 sensor lineup.  There has not been a true "back illuminated" Micro 4:3 sensor.  That should have been the natural development step before the APS-C and Full Frame sensors.  Yet magically, Sony was able to come up with APC-C and Full Frame back illuminated sensors (a6500 and the a7iii).  Hmm...



The cost differential for BSI is leveling out but has to date remained a factor of consequence in determining the camera model price point where it is introduced.

Joe


----------



## vin88

VidThreeNorth said:


> This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.
> 
> *"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler


   I know what ASA does for film.   never knew what ISO did.   now in the digital age,  its point and shoot,  dam the consequences.


----------



## Designer

vin88 said:


> I know what ASA does for film.   never knew what ISO did.   now in the digital age,  its point and shoot,  dam the consequences.


Actually, when some of us try to create a certain image, we will use some or all the tools that were used in film technology PLUS any digital tools we need. 

Digital is not "better" in terms of image quality, but it certainly opens up many more possibilities than with film alone. 

The "point and shoot" folks haven't tried to learn photography, and assume (erroneously) that among the many images they capture, they will get one or two "keepers".  This is like fishing with a net and hoping to catch a trophy.  I think you can safely ignore the "spray and pray" crowd and their limited view of art and the world.


----------



## Ysarex

vin88 said:


> VidThreeNorth said:
> 
> 
> 
> This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.
> 
> *"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler
> 
> 
> 
> I know what ASA does for film.   never knew what ISO did.   now in the digital age,  its point and shoot,  dam the consequences.
Click to expand...


ASA? ....dam the consequences? WTF?!

I started in photography when ASA was the film sensitivity standard here in the US. I've followed along and kept up through the transition to digital and continue to enjoy taking photographs as I did 40 years ago.

Whatever it is that you're trying to say or comment on I suspect is predominantly your problem.

Joe


----------



## Digital Matt

I think you guys are obfuscating the issue in an attempt to be overly technically correct. 

Is digital ISO the same as ASA/ISO for film? Simple, straightforward answer, YES! 

It's the sensitivity of the sensor. How that sensitivity is achieved from a technical standpoint and how it is the same or different from film does not matter. It makes your sensor more sensitive to light. It's part of the exposure triangle. That's all you need to know to get started understanding it and making images. That's how you "use" it. If you want to delve deeper into understanding it then you can do so at your leisure, but if you are having trouble understanding the concept, get that first.

f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100. It's that simple.


----------



## Ysarex

Digital Matt said:


> I think you guys are obfuscating the issue in an attempt to be overly technically correct.
> 
> Is digital ISO the same as ASA/ISO for film? Simple, straightforward answer, YES!
> 
> It's the sensitivity of the sensor. How that sensitivity is achieved from a technical standpoint and how it is the same or different from film does not matter. It makes your sensor more sensitive to light. It's part of the exposure triangle. That's all you need to know to get started understanding it and making images. That's how you "use" it. If you want to delve deeper into understanding it then you can do so at your leisure, but if you are having trouble understanding the concept, get that first.
> 
> f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100. It's that simple.



Everything above is so wrong. It is confusing to beginners and it fosters the adoption of bad practice.

Couple questions for you:
Do you know what the current ISO standard defines for digital photography?
What are the resulting characteristics of a photo taken using an APS-C camera at ISO 12,800?
Can you define exposure?
Based on the industry standard definition of exposure please explain how this works: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100."

Joe


----------



## Digital Matt

I'm not going to engage with you on this because you are clearly crazy.


----------



## Ysarex

Digital Matt said:


> I'm not going to engage with you on this because you are clearly crazy.



OK -- let's just leave it at everything you said is technically way wrong but you prefer a model of error and ignorance because it helps you understand stuff.

Joe


----------



## smoke665

Joe is correct and is highly knowledgeable about the technical aspects of photography. He is the unofficial walking, talking encyclopedia of knowledge here on TPF, who has been a valuable source of knowledge for many of us, myself included. ISO, as it relates to a digital camera, has nothing to do with the sensor. The gain is nothing more than an amplification of the signal obtained from the sensor which I believe has already been mentioned several times.


----------



## Digital Matt

Once again, your obfuscating the issue. ISO is one of three controls of exposure. The OP has been a film shooter for years and clearly understands how to use ISO with regard to film, but is hitting a stumbling block with digital, by reading overly complex, technical focused stuff. You did nothing to help him understand how to use ISO to make photos. It's clear that you are here to talk technology to the nth degree. I use technology to make images. I gave a simple straightforward answer that was not wrong, not in any way. ISO provides the same function on a digital camera that it does with a film camera. I fully understand that it does not do it in the same way. They are completely different technologies, obviously. Knowing when/where/how the camera amplifies the signal in no way helps you make better images.

I came back to this forum after a decade long hiatus and I see not much has changed. Maybe this will be short lived.


----------



## vin88

Ysarex said:


> vin88 said:
> 
> 
> 
> 
> 
> VidThreeNorth said:
> 
> 
> 
> This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.
> 
> *"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler
> 
> 
> 
> I know what ASA does for film.   never knew what ISO did.   now in the digital age,  its point and shoot,  dam the consequences.
> 
> Click to expand...
> 
> 
> ASA? ....dam the consequences? WTF?!
> 
> I started in photography when ASA was the film sensitivity standard here in the US. I've followed along and kept up through the transition to digital and continue to enjoy taking photographs as I did 40 years ago.
> 
> Whatever it is that you're trying to say or comment on I suspect is predominantly your problem.
> 
> Joe
Click to expand...

    just American English,  not a problem for me.  vin


----------



## Ysarex

Digital Matt said:


> Once again, your obfuscating the issue.



I'm clearing up the profound confusion that you're flailing around in and that led you to write down this nonsense: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100."



Digital Matt said:


> ISO is one of three controls of exposure. The OP has been a film shooter for years and clearly understands how to use ISO with regard to film, but is hitting a stumbling block with digital, by reading overly complex, technical focused stuff. You did nothing to help him understand how to use ISO to make photos. It's clear that you are here to talk technology to the nth degree.



I thought you weren't going to engage on this! Yet already it's amazing how much you know about me!! WOW!



Digital Matt said:


> I use technology to make images.



You don't say.



Digital Matt said:


> I gave a simple straightforward answer that was not wrong, not in any way.



This is wrong: "It's the sensitivity of the sensor."
This is wrong: "How that sensitivity is achieved from a technical standpoint and how it is the same or different from film does not matter."
This is wrong: "It makes your sensor more sensitive to light."
This is major wrong: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100."



Digital Matt said:


> ISO provides the same function on a digital camera that it does with a film camera. I fully understand that it does not do it in the same way. They are completely different technologies, obviously. Knowing when/where/how the camera amplifies the signal



Who said it amplifies the signal? That's one of the things the OP was confused about and I sent him to a website where he can get clear answers instead of nonsense.



Digital Matt said:


> in no way helps you make better images.



Understanding how and why things work may not always be necessary but it is not harmful and it can be both helpful and satisfying. The OP was asking about a technical article and I gave him references where he could get additional info.



Digital Matt said:


> I came back to this forum after a decade long hiatus and I see not much has changed. Maybe this will be short lived.



Where you came from and where you're going has nothing to do with ISO.

The current ISO standard was revised in 2006 to address digital cameras (ISO 12232:2006) and provides more than one option for establishing ISO values. Most camera manufacturers use the SOS (standard output sensitivity) measure which does not reference the sensor -- it is not the sensitivity of the sensor but is determined by the brightness values in the camera software processed JPEG. reference -- It can be useful to understand that.

Even during the good ol' days of film ISO was never an exposure determinant by the standard definition of photographic exposure: "When a photograph is taken, light from the various areas of the subject falls on corresponding areas of the film for a set time. The effect produced on the emulsion is, within limits, proportional to the product of the illuminance E and the exposure time t. We express this by the equation H = Et Before international standardization of symbols, the equation was E = It (E was exposure, I was illuminance) and this usage is sometimes still found. The SI unit for illuminance is the lux (lx). Hence the exposure is measured in lux seconds (lx s)." (from Ilford's The Manual of Photography, 9th edition p. 218)

This one's a little simpler and easier to understand: "In photography, *exposure* is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance."

Notice that ISO isn't identified in either definition as a factor that determines exposure which goes a long way to explaining why this: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100." is so very very wrong.

What the camera records is bottom line a function of exposure. Raising the ISO most certainly does not add more light which would be more exposure. That is, as my old Latin teacher would say, bass ackwards.

Joe


----------



## Fujidave

Just reading through the last couple of posts, and I am lost on what to believe or think.


----------



## snowbear

Fujidave said:


> Just reading through the last couple of posts, and I am lost on what to believe or think.


All I know is when I increase the ISO, the meter in the camera swings toward the “lighter” side and I can speed up the shutter and/or use a smaller aperture to center it.  When I decrease the ISO, the opposite happens.


----------



## Digital Matt

The essential elements of photography like exposure, have not changed in over 100 years. You can pick up a photography book from 70s, read up on shutter speed, aperture, and ISO, go pick up a digital camera, put it in manual, and start shooting successfully, employing that knowledge. You can believe that by trying it out yourself.


----------



## Fujidave

The one thing I do know is, to take a photo you need Light.  So for me I have to really learn the Exposure Triangle, if I am right that is Shutter speed, Aperture and ISO.  That`s if I read it all right that is.


----------



## Ysarex

Fujidave said:


> Just reading through the last couple of posts, and I am lost on what to believe or think.



It's not difficult to understand. First understand this: When the transition from film to digital began it was easiest to try and keep things feeling familiar. Lots of film photographers got their first digital cameras and rather than explain what was actually going on the simple answer was, "it's just like film." At the same time the industry was still figuring it out! I got my first digital camera in 2002. There was no ISO standard for digital cameras at that time. It didn't come along until 2006! (ISO 12232:2006). In the meantime a bazillion self-publishing experts got busy creating all those Youtube videos explaining it all. 

If you want to actually read the ISO standard you have to pony up some serious $$$ as selling the details is how ISO pays the bills. In this case however there's a free way around it. In 2006 what ISO did was simply adopt the standard from CIPA (Camera & Imaging Products Association) of which all our camera manufacturers are members. CIPA - Camera & Imaging Products Association: CIPA Standards Specifically you're looking for this document: http://www.cipa.jp/std/documents/e/DC-004_EN.pdf

I've read it and if you want to avoid slogging through it you can trust me to tell you that the ISO "sensitivity" values that you find on your camera are arrived at by measuring the brightness produced in a sRGB JPEG generated by your camera's processing software when exposed to a standard target. Who cares right? Well Fujidave might care eventually since he's shooting a Fuji camera. Since ISO is not a measure of the light sensitivity of the camera sensor is it possible that's actually different and could that matter to the photos you take? The answer is yes and yes especially if you're shooting a Fuji camera -- I shoot a Fuji too.

Next: Changing ISO on your camera does not change the sensitivity of anything. ISO on your camera does two things: a) It puts a spin on the metering systems and the camera meter calculates a new exposure. As you raise the ISO value the camera calculates an exposure reduction and as you lower the ISO the camera calculates an exposure increase. Many people confuse this ancillary function and make the spurious jump to thinking ISO therefore determines exposure at least in part. It does not. b) ISO boosts, brightens, gains (description of this process is tricky because old words like amplify have connotations that aren't quite right and multiple technologies are employed) the analog data coming from the sensor prior to and/or during ADC (analog to digital conversion) to normalize brightness in the raw file from which the JPEG is then created.

Joe


----------



## Ysarex

Digital Matt said:


> The essential elements of photography like exposure, have not changed in over 100 years. You can pick up a photography book from 70s, read up on shutter speed, aperture, and ISO, go pick up a digital camera, put it in manual, and start shooting successfully, employing that knowledge.



That's exactly why I used good old Ilford's _The Manual of Photography_ up above to prove you wrong. First published in 1890 and still the go to reference when you want to get your photography right!



Digital Matt said:


> You can believe that by trying it out yourself.


----------



## Fujidave

Ysarex said:


> Fujidave said:
> 
> 
> 
> Just reading through the last couple of posts, and I am lost on what to believe or think.
> 
> 
> 
> 
> It's not difficult to understand. First understand this: When the transition from film to digital began it was easiest to try and keep things feeling familiar. Lots of film photographers got their first digital cameras and rather than explain what was actually going on the simple answer was, "it's just like film." At the same time the industry was still figuring it out! I got my first digital camera in 2002. There was no ISO standard for digital cameras at that time. It didn't come along until 2006! (ISO 12232:2006). In the meantime a bazillion self-publishing experts got busy creating all those Youtube videos explaining it all.
> 
> If you want to actually read the ISO standard you have to pony up some serious $$$ as selling the details is how ISO pays the bills. In this case however there's a free way around it. In 2006 what ISO did was simply adopt the standard from CIPA (Camera & Imaging Products Association) of which all our camera manufacturers are members. CIPA - Camera & Imaging Products Association: CIPA Standards Specifically you're looking for this document: http://www.cipa.jp/std/documents/e/DC-004_EN.pdf
> 
> I've read it and if you want to avoid slogging through it you can trust me to tell you that the ISO "sensitivity" values that you find on your camera are arrived at by measuring the brightness produced in a sRGB JPEG generated by your camera's processing software when exposed to a standard target. Who cares right? Well Fujidave might care eventually since he's shooting a Fuji camera. Since ISO is not a measure of the light sensitivity of the camera sensor is it possible that's actually different and could that matter to the photos you take? The answer is yes and yes especially if you're shooting a Fuji camera -- I shoot a Fuji too.
> 
> Next: Changing ISO on your camera does not change the sensitivity of anything. ISO on your camera does two things: a) It puts a spin on the metering systems and the camera meter calculates a new exposure. As you raise the ISO value the camera calculates an exposure reduction and as you lower the ISO the camera calculates an exposure increase. Many people confuse this ancillary function and make the spurious jump to thinking ISO therefore determines exposure at least in part. It does not. b) ISO boosts, brightens, gains (description of this process is tricky because old words like amplify have connotations that aren't quite right and multiple technologies are employed) the analog data coming from the sensor prior to and/or during ADC (analog to digital conversion) to normalize brightness in the raw file from which the JPEG is then created.
> 
> Joe
Click to expand...



Thank you very much for this, as you have helped me in the past I will gladly listen and take it on board.


----------



## Ysarex

Fujidave said:


> The one thing I do know is, to take a photo you need Light.  So for me I have to really learn the Exposure Triangle, if I am right that is Shutter speed, Aperture and ISO.  That`s if I read it all right that is.



The Exposure Triangle can be initially helpful but it does lead to confusion. Typically it's presented like this:




 

Suggesting that each vertice of the triangle is an exposure control (shutter, aperture, ISO) and that each of those variables controls a secondary element of your photo;
shutter = motion blur
aperture = DOF
ISO = noise.

People who learn with that model tend to adopt some misconceptions. For one they assume ISO is an exposure determinant and it is not. More importantly they make the mistake of assuming that ISO causes noise -- that noise is the result of raising the ISO and that's wrong.

SET A
1/250th sec, f/5.6, ISO 200
1/500th sec, f/4, ISO 200
1/125th sec, f/8, ISO 400
~~~~~~~~~~~~~~~~~~~~~~

SET B
1/250th sec, f/5.6, ISO 200
1/500th sec, f/4, ISO 200
1/250th sec, f/8, ISO 400
~~~~~~~~~~~~~~~~~~~~~

Two sets above: all three in each set the same exposure yes, no?

There are weaknesses in the model and even though it may seem at first helpful for beginners it typically results in misunderstanding. I deal with it every semester with a new batch of students. They arrive already "exposure triangle" indoctrinated and they're taking worse photos than they should be because of the misconceptions I've noted above. Once I can get those misconceptions cleared up I can help them take better photos.

You're shooting a Fuji X camera with an APS-C sensor. What kind of results do you get at ISO 12,800? I have the same sensor in my camera. Have a look at this photo I shot at ISO 12,800 socks and tell me what you think about the noise level.

Joe


----------



## Fujidave

As you might know Joe, I am still learning with both my Fuji X cameras, the socks image is great as if I am right you have exposed it bang on with no noise at all ?


----------



## Fujidave

I will try and dig out a photo, but last week using the X-T2 + XF 35mm f2 in a pub.  Lighting was turned right down and it waas dark out side even though I was in side, had to put the iso up to 800 and deleted them all as they were terrible when I got them in LR6 and hit the exposure slider, then I went again but this time same sort of lighting turned down, iso 640 and the shots were not to bad.


----------



## Ysarex

Fujidave said:


> As you might know Joe, I am still learning with both my Fuji X cameras, the socks image is great as if I am right you have exposed it bang on with no noise at all ?



The socks image was taken indoors in low light and the camera ISO is set to 12,800. I did put the camera on a tripod and what I did to keep the noise down was to expose as much as possible.

There's the exposure triangle problem and the connection of noise to ISO. Noise in your photos, especially with your Fuji camera, is going to be a function of exposure. Exposure is how much physical light strikes the sensor and ISO is NOT part of that -- just shutter speed, f/stop and image brightness. I deliberately picked the socks scene because it had a low dynamic range (low contrast) and what I did was expose as much as the sensor would tolerate -- like a +2.3 EC. I knew something about ISO and Fuji. ISO is not a rating of the sensor sensitivity and Fuji hedges the sensor by a good solid stop. In other words when you get a good exposure JPEG from a Fuji camera odds are the sensor could have handled at least a stop more exposure. Given a low contrast scene even more exposure was possible without clipping the sensor and I pushed for all of it. The camera JPEG I got was overexposed badly but the raw file was not and because noise is a function of exposure the exposure increase I applied reduced the noise even at ISO 12K.

By the way in those two sets above all three exposures in SET A are the same whereas the last exposure in SET B is less.

Joe


----------



## Ysarex

Fujidave said:


> I will try and dig out a photo, but last week using the X-T2 + XF 35mm f2 in a pub.  Lighting was turned right down and it waas dark out side even though I was in side, had to put the iso up to 800 and deleted them all as they were terrible when I got them in LR6 and hit the exposure slider, then I went again but this time same sort of lighting turned down, iso 640 and the shots were not to bad.



Odds are you were making the exact same mistake my students make because the "exposure triangle" has taught them to be afraid of ISO. So what they'll typically do is resist raising the ISO and at the same time not expose enough thinking that's better than raising the ISO even more. If the circumstance requires it RAISE THE ISO so that if anything you seem to be exposing too much for that ISO -- doing the opposite is what clobbers you.

Joe


----------



## Fujidave

I have checked but deleted the shots, but what I remember was.  Full Manual mode iso 800 shutter speed think was 1/100 and aperture was f7.1 I think. Lens was the XF 18-55mm.


----------



## Fujidave

First shot is of Abi, 1/100 ss, iso 640 f4.5 lens was XF18-55mm and it was evening time out side so dark.




 


2nd shot is Marilyn du Sax. f2 1/100 ss and iso 640 lens was XF 35mm.  Camera used on both was the X-T2.


----------



## Ysarex

Fujidave said:


> First shot is of Abi, 1/100 ss, iso 640 f4.5 lens was XF18-55mm and it was evening time out side so dark.
> 
> View attachment 161917
> 
> 
> 2nd shot is Marilyn du Sax. f2 1/100 ss and iso 640 lens was XF 35mm.  Camera used on both was the X-T2.
> 
> View attachment 161918



So if these are JPEGs from the camera you have the potential to increase the quality and reduce the noise by 1. (best) increase the exposure (shutter/aperture) or 2. (not quite as good) increase the ISO and in either case process a raw file. The question remains by how much can you do either 1. or 2. and the answer is likely a stop or more but testing first is the best practice.

Joe


----------



## Fujidave

Ysarex said:


> Fujidave said:
> 
> 
> 
> First shot is of Abi, 1/100 ss, iso 640 f4.5 lens was XF18-55mm and it was evening time out side so dark.
> 
> View attachment 161917
> 
> 
> 2nd shot is Marilyn du Sax. f2 1/100 ss and iso 640 lens was XF 35mm.  Camera used on both was the X-T2.
> 
> View attachment 161918
> 
> 
> 
> 
> So if these are JPEGs from the camera you have the potential to increase the quality and reduce the noise by 1. (best) increase the exposure (shutter/aperture) or 2. (not quite as good) increase the ISO and in either case process a raw file. The question remains by how much can you do either 1. or 2. and the answer is likely a stop or more but testing first is the best practice.
> 
> Joe
Click to expand...


So I need to get as much practice as I possibly can then.


----------



## Fujidave

Hi Joe, if this is the book you were talking about.  Would it help me if I bought it ?


https://www.amazon.co.uk/Manual-Pho...862&sr=1-1&keywords=The+Manual+of+Photography


----------



## john.margetts

Ysarex said:


> Digital Matt said:
> 
> 
> 
> I'm not going to engage with you on this because you are clearly crazy.
> 
> 
> 
> 
> OK -- let's just leave it at everything you said is technically way wrong but you prefer a model of error and ignorance because it helps you understand stuff.
> 
> Joe
Click to expand...

The thing is, Joe, it does help. It can ease a snap-shooter into being a more considered photography. The down side is that eventually the photographer comes up against a brick wall and can proceed no further as the incorrect but useful stuff is now incorrect and a hinderance.

Learning the technicalities is best and for those of us with a technical background that is rather easy. For people who left school with nothing, the technicalities might as well be written in ancient Sanskrit as they will understand nothing. Your students - by virtue of being students - have already demonstrated both a willingness and an ability to learn new stuff so teach them correctly. Those that are going to progress a bit and no further need something and if that something is a dead-end, it will not matter to them.


----------



## Ysarex

Fujidave said:


> Hi Joe, if this is the book you were talking about.  Would it help me if I bought it ?
> 
> 
> https://www.amazon.co.uk/Manual-Pho...862&sr=1-1&keywords=The+Manual+of+Photography



Think of it as a technical reference when you want to look something up rather than an instructional read. So save some $$ and buy the previous edition: https://www.amazon.co.uk/Manual-Pho..._rd_t=40701&psc=1&refRID=P7R9WDN0ZPE9W8YMGRKD

Joe


----------



## smoke665

Ysarex said:


> deliberately picked the socks scene because it had a low dynamic range (low contrast) and what I did was expose as much as the sensor would tolerate -- like a +2.3 EC. I



I haven't really dived into the way it works, but could this be how the "High ISO Noise Reduction" setting on my Pentax works? Doing it automatically?


----------



## vin88

WOW !  ISO guys,  give it a rest.


----------



## Ysarex

john.margetts said:


> Ysarex said:
> 
> 
> 
> 
> 
> Digital Matt said:
> 
> 
> 
> I'm not going to engage with you on this because you are clearly crazy.
> 
> 
> 
> 
> OK -- let's just leave it at everything you said is technically way wrong but you prefer a model of error and ignorance because it helps you understand stuff.
> 
> Joe
> 
> Click to expand...
> 
> The thing is, Joe, it does help. It can ease a snap-shooter into being a more considered photography. The down side is that eventually the photographer comes up against a brick wall and can proceed no further as the incorrect but useful stuff is now incorrect and a hinderance.
> 
> Learning the technicalities is best and for those of us with a technical background that is rather easy. For people who left school with nothing, the technicalities might as well be written in ancient Sanskrit as they will understand nothing. Your students - by virtue of being students - have already demonstrated both a willingness and an ability to learn new stuff so teach them correctly. Those that are going to progress a bit and no further need something and if that something is a dead-end, it will not matter to them.
Click to expand...


When you say "it does help" I'm not entirely sure what "it" is. Are you talking about the "exposure triangle" or the misconception that ISO alters sensor light sensitivity or the misconception that ISO alters exposure or the misconception that ISO causes noise or the misconception that digital ISO is the same as film ISO or all of the above? I understand that the "exposure triangle" can be helpful and I acknowledged that:


Ysarex said:


> The Exposure Triangle can be initially helpful but it does lead to confusion.


In my class notes that I hand out to students I also acknowledge that: "_It's a simple illustration that can admittedly help beginners get a grasp of the concepts that 1. correct exposure of film or a digital sensor is in fact a fixed constant -- the same total quantity of light is always required for a specific ISO value, and 2. the controls on the camera for shutter and aperture can be (must be) reciprocally adjusted for exposure while independently altering the rendition of motion and depth of field. Those are two important concepts to grasp and beginners seem to catch on with this illustration so why am I complaining._" I acknowledge it again in the last paragraph of the same notes: "_Unfortunately it's too late to fix it, this genie isn't going back in the bottle. And that does mean that a lot of people derive value from learning with this model misunderstanding or not. It's popular for a reason. They can learn to use their cameras pretty effectively even though maintaining misconceptions about how they function. This isn't the worst popular misconception about photography. But this is a college class so when you get this wrong on the test _*I'm still getting out the red pen."
*
So what we have in this thread is precisely what you note; an OP hitting a brick wall as the useful stuff just got revealed as incorrect and is now a hindrance.  VidThreeNorth just encountered a technical article You probably don't know what ISO means – and that's a problem and is struggling to process that information. Do we tell him, "Don't look behind that curtain, just close the curtain and back away -- forget what you saw? If you lift the hood the hamsters will run away!" This is a thread where the OP specifically asked for some help understanding what's behind the curtain.

Joe


----------



## Ysarex

smoke665 said:


> Ysarex said:
> 
> 
> 
> deliberately picked the socks scene because it had a low dynamic range (low contrast) and what I did was expose as much as the sensor would tolerate -- like a +2.3 EC. I
> 
> 
> 
> 
> I haven't really dived into the way it works, but could this be how the "High ISO Noise Reduction" setting on my Pentax works? Doing it automatically?
Click to expand...


No, High ISO Noise Reduction in your camera is a noise filter that's applied to the camera's JPEG output. In camera noise filters tend to generate weaker results than the noise filtering we can apply during processing. The problem the camera manufacturers face is the requirement to generate JPEG results very quickly. Your K3 has to be able to output JPEGs at a multiple frames per second rate and that typically dictates some corner cutting in the processing software. A computer hosted noise filter like DX0's Prime or DeNoise can be pretty processor intensive.

Noise filtering helps a lot and I use it all the time, but the real bottom line is exposure. The noise we all see in our photos that we don't like is shot noise and shot noise is a function of exposure. We raise the ISO on our cameras when we don't have enough light to either achieve a hand-holdable shutter speed or the f/stop we want for DOF. Without enough light we start to reduce exposure and that's the cause of the noise. Unfortunately a lot of photographers and especially beginners reduce exposure more than necessary and they complicate the problem by resisting raising the ISO. Contrary to popular misunderstanding, the electronics behind ISO typically suppress the noise caused by the exposure reduction. In the case of the example I posted, I took advantage of the fact that the camera's tend to hedge the tuning of their metering systems toward reduced exposure -- given a choice between possibly blowing highlights versus a stop less exposure they opt for what they see as the lesser evil and adjust their camera's meters to generate a good JPEG from a sensor exposure that is less than the sensor can tolerate. By pushing to the sensor's real limit I can increase exposure by more than double what the camera meter suggests and I get a lot less noise for it.

I'm enjoying my new P&S compact camera (Canon G7xii) which has a 1 inch sensor. I use it at ISO 12,800 if needed but I expose to keep the noise as low as possible. I posted this image a couple weeks ago: Gruesome Assault and if you look at the exif data you'll see I have a +1 EC set. The camera meter would have applied only 1/2 the exposure that I did. Yes it's noise filtered and I use good tools but the real bottom line is I applied twice as much exposure as the camera would have. That gave me a blown out JPEG and the requirement that I process the raw file -- that's how this game works.

Joe


----------



## Fujidave

vin88 said:


> WOW !  ISO guys,  give it a rest.



For me and only me all this iso is big, I want to be able to up my iso and not worry at all when in the pubs and clubs shooting


----------



## Grandpa Ron

Nothing mysterious here, in the old days you controlled the shutter speed and aperture and loaded your camera with the film speed (ISO) you thought you would need. Maybe you could push it or pull it in the darkroom a bit.

With digital you still control the shutter speed, aperture and now you can also change the film speed between shots.

You still have the same issues however. the faster you push the ISO the "grainer", it called noise these days, the picture.

As always, good photography requires knowledge of all the effects of the camera's variables. With digital you have many more right at your fingertips.


----------



## Ysarex

Grandpa Ron said:


> Nothing mysterious here, in the old days you controlled the shutter speed and aperture and loaded your camera with the film speed (ISO) you thought you would need. Maybe you could push it or pull it in the darkroom a bit.
> 
> With digital you still control the shutter speed, aperture and now you can also change the film speed between shots.
> 
> You still have the same issues however. the faster you push the ISO the "grainer", it called noise these days, the picture.



Well Grandpa, some help here then as I seem to have a mystery on my hands. According to you faster (higher) ISO values are going to make my photo "grainier" -- noisy. But that doesn't seem to be happening. I just took these two photos:






One at ISO 125 and the other at ISO 1600 and the higher ISO photo doesn't look any noisier than the lower ISO photo. In fact if anything the higher ISO photo is maybe a smidge less noisy. What's the deal?

Here's both photos at full res so you can pixel peep them:

ISO 125
ISO 1600

They were both processed with luminous noise filtering turned off so as not to interfere. Why isn't the ISO 1600 photo noisier than the ISO 125 photo?

Joe



Grandpa Ron said:


> As always, good photography requires knowledge of all the effects of the camera's variables. With digital you have many more right at your fingertips.


----------



## Derrel

Yogi Bear might have something to say in this thread, should he appear. I miss seeing Yogi.  The last time I saw him was back in the ASA 64 Kodachrome era.


----------



## Ysarex

Derrel said:


> Yogi Bear might have something to say in this thread, should he appear. I miss seeing Yogi.  The last time I saw him was back in the ASA 64 Kodachrome era.


----------



## Overread

Ysarex in fairness for your test you've kind of got to mention the camera you are using now since its not just a case of exposure methods (eg expose to the right) helping to keep noise down; but also because some brands (eg Nikon and Sony) now have sensors which have tiny amounts of noise even if you recover from underexposure; whilst Canon and some other brands are still using sensors that require correct exposure otherwise any brightening can result in increased noise.


----------



## smoke665

Without getting technical, it's my understanding that my K1MII has several thousand tiny little maintenance workers with brooms that run all over the sensor sweeping up the excess noise whenever I go into the mega ISO stage.


----------



## Ysarex

Overread said:


> Ysarex in fairness for your test you've kind of got to mention the camera you are using now since its not just a case of exposure methods (eg expose to the right) helping to keep noise down; but also because some brands (eg Nikon and Sony) now have sensors which have tiny amounts of noise even if you recover from underexposure; whilst Canon and some other brands are still using sensors that require correct exposure otherwise any brightening can result in increased noise.



It's all in the EXIF data but sure; Canon G7xii.

Joe

P.S. The move toward ISO invariant sensors is well underway. That Canon G7 I'm using is functionally ISO invariant and you mentioned Canon specifically as a make that in years past was not. And so considering that, what you're acknowledging is what that illustration shows: the source of the noise isn't something that ISO is doing in the camera. In fact quite the opposite; what ISO does internally in the camera elctronics either suppresses noise or is noise neutral. Just trying to help Grandpa Ron get cause and effect straight in this case.


----------



## Overread

Yeah I'm not surprised Canon is moving in the same direction with the technology - they could hardly not otherwise Nikon and the others would leave them in the dust. The ISO invariant tech is probably going to be one of the biggest (if also oddly quite quietly released) events in the camera world since almost removing the pressure of proper exposure vastly increases creative possibilities for many photographers. 


I will be interested in seeing what comes next year from Canon - they've a few lines that are ripe for an update with newer age sensors!


----------



## Ysarex

Overread said:


> Yeah I'm not surprised Canon is moving in the same direction with the technology - they could hardly not otherwise Nikon and the others would leave them in the dust. The ISO invariant tech is probably going to be one of the biggest (if also oddly quite quietly released) events in the camera world since almost removing the pressure of proper exposure vastly increases creative possibilities for many photographers.



It's oddly quiet because all of the camera manufacturers are focused on their camera's JPEG output in which case ISO invariance is irrelevant.

You can think about it as removing pressure for proper exposure but that makes me cringe so I'm going to prefer to think about it as expanding the possibilities for creativity. That's why a correct understanding of what's happening under the hood can matter. I regularly take photos that people who are stuck thinking digital ISO is just like film can't take at all.

Consider this difference between film/ISO and digital/ISO: As you raise film ISO you also typically increase DR capacity -- faster films have an increased ability to record a larger dynamic range. Digital/ISO is the exact opposite. As you increase ISO on a digital camera you're chopping off DR. Nobody seems to learn that. It's not on the exposure triangle -- just ISO = noise (and it doesn't). Now let's put that fact and ISO invariance together and see what happens with a high DR scene. I grabbed a couple baskets and stuck them in front of the window. Again the Canon G7:



 

I didn't bother to match the color because what's of concern here is the highlights. I set the camera to expose for the baskets at ISO 3200 and got an exposure of 1/30th sec at f/8. The highlights in the curtain and out the window are nuked in the raw file -- unrecoverable. So I kept the same exposure but dropped the ISO to 125. At ISO 3200 the G7 has a DR capacity of 4.5 stops. At ISO 125 it's DR capacity is 9 stops. That's double! In the photo on the left I used the 9 stops and kept the detail in the curtain but in the photo on the right I didn't have 9 stops. In the ISO 125 camera JPEG there is no bookcase and decorative chair -- just solid black. But at the same exposure it's recorded just as well as it is in the ISO 3200 photo. To keep the highlights in the ISO 3200 photo I'd have to reduce the exposure which is the last thing I want to do for the basket and the room interior -- basically not possible with only 4.5 stops of DR.

Knowing how the machine works lets you use it to full advantage.

Joe



Overread said:


> I will be interested in seeing what comes next year from Canon - they've a few lines that are ripe for an update with newer age sensors!


----------



## Original katomi

VidThreeNorth said:


> This is something I have been struggling with, and after reading this article, I'm still struggling.  I "grew up" in film and I understand film ISO.  I also understand the basics of electronic sensors.  So I should see a digital ISO and know what it is telling me, right?  Well, I really don't.  I just use it like I was using a film camera as best as I can.
> 
> *"You probably don't know what ISO means – and that's a problem*" Published Aug 6, 2018 | Richard Butler


Hi you grew up with iso I grew up with ASA lol and yes I do the same as you  and  I tend to play with the camera and the ISO /appature/shutter speed settings to see what changes


----------

