# Understanding Exposure - Peterson - metering



## mdsnyderjr (Apr 6, 2012)

I'm trying to convince myself to start shooting in manual so I'm re-reading Bryan Peterson's book Understanding Exposure.  The book mentions (almost every photo) that Bryan meters off of something, usually the sky.  Is he using spot metering?  It seems like it wouldn't matter where you point if you are using matrix metering.  With matrix metering, do I even need to "meter" off of anything or do I just pick my shutter speed and set the aperture to a correct exposure (or vice versa)?

I have a Nikon, D5100.


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## dxqcanada (Apr 6, 2012)

He is metering a specific area ... most likely with a spot meter (a centre weight meter could be used but not so accurate).

Matrix metering is the computerized version of a human spot metering multiple areas and figuring out an optimal exposure.


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## mdsnyderjr (Apr 6, 2012)

So is there any point to "metering" off of something if I put my camera in matrix mode?


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## dxqcanada (Apr 6, 2012)

Not if you want to figure out the exposure for yourself.

If you want to manually (use your brain) control exposure ... then use Spot Metering, on the areas.


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## SCraig (Apr 6, 2012)

Matrix metering is going to average all of the tones in its sampling area and come up with a value that matches neutral gray.  If there is a lot of sky in the shot the subject will probably be underexposed.  If there is a lot of shadow the subject will probably be overexposed.  Using spot metering, or center weighted, shows the proper exposure FOR ITS SAMPLING AREA (which is usually very small) and ignores anything outside the sampling area.  If, for example, you sample the white dress on a bride using spot metering then her face will probably be underexposed.  If you sample a shadowed area with spot metering, or a dark area on an animal, the rest of the image will probably be overexposed.  It is always a balancing act and you have to pick the proper area to meter from or trust your camera to meter the subject area properly.

I frequently meter on a small neutral gray card I keep in my camera bag.  If I don't have it handy I've found that metering on the palm of my hand will give a very close exposure value.


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## scorpion_tyr (Apr 6, 2012)

If you meter off a specific area you're either using spot metering or a handheld light meter.


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## ph0enix (Apr 6, 2012)

mdsnyderjr said:


> So is there any point to "metering" off of something if I put my camera in matrix mode?



if you point the camera at the sky, you'll get a different reading than when you point it at the ground regardless of the selected metering mode.  
Pick up the camera and experiment.  See how moving it changes the meter readings.


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## Crollo (Apr 6, 2012)

I really don't understand what you're trying to figure out here... With a scene that does not exceed the dynamic range of your medium, it doesn't matter. If your scene exceeds the dynamic range of your medium, then _you figure it out. We can't decide for you what should be exposed in YOUR image. _Is the terrain in your scene the dominant subject, or is the sky the dominant subject in the scene? Expose for what you want to be exposed and blow out or crush the other... Simple.


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## dxqcanada (Apr 6, 2012)

From Nikon:

[SIZE=+1]*Matrix Meter is called the 3D RGB Color Matrix Meter.* 
[/SIZE] This meter gathers information from 1005 red, green, and  blue sensors and factors in distance information provided by the lens as  it evaluates proper exposure calculation. This meter instantly analyzes  a scene&#8217;s overall brightness, contrast, and other lighting  characteristics, comparing what is sees against an onboard database of  over 30,000 images for unsurpassed exposure accuracy, even in the most  challenging photographic situations. By the time the 3D Matrix meter has  made its considerations of colors by hue and saturation, tonal ranges  by brightest and darkest, areas of similar tonality that are connected  or separated, distance to the subject, and compared that to its database  generated from photographic images, it&#8217;s got a very good idea of what  the exposure should be. 

If you are a beginner, Matrix is where you should start. As your skills  grow, and they will, you will acquire a better understand of when it  might be beneficial to use other light metering options. 

*What is the database of over 30,000 images?* 
Over the years Nikon has studied the color, area of coverage, focus  distance, contrast, size and shape of shadows and highlights and  exposure characteristics of over 30,000 actual photographic images and  incorporated this data as a reference source for the expert exposure  system that is the 3D Color Matrix Meter.


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## petto (Apr 7, 2012)

^^except that you know how your camera works and can make it do it what you want it to and are able understand how you got the picture you got.  

Other than that it is pretty meaningless...........


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## petto (Apr 7, 2012)

I disagree, using your camera in modes other than auto can teach you a lot (along with some research). You can adjust the ISO, aperture, and shutter speed and see the effects those make on the end result. Doing this in different lighting situations will give you look at how these different aspects of your camera's settings will effect the exposure of you pictures. 

I am in no way saying that simply by switching the dial to "M" you will automatically know more. I am merely suggesting that in order to better understand how ones camera works you have to eventually step out of auto mode to understand the "why" behind the outcome.


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## dxqcanada (Apr 7, 2012)

I learned exposure by shooting the same subject at different settings (shutter speed/aperture) and over/under exposing based on the camera's meter reading. I noted each setting so when I got the images back I could examine what occured with each change.
Doing this on different subjects and under different lighting conditions, I was able to understand how to expose/meter.

Using manual exposure requires some understanding of how the camera's light meter works, and also being able to adjust it to expose the image as you visualized.

< not sure if I said this as I intended >


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## impulsive1 (Apr 8, 2012)

Graystar said:


> Understanding Exposure is practically from another era, first published in 1990.  Pro cameras didn't have multi-segment metering (Matrix for Nikon, Evaluative for Canon) until 87/88, so he's likely referring to center-weighted/partial metering modes.  I personally don't think much of that book.
> 
> Matrix metering is the "auto-everything" of metering modes.  It sets your exposure for you.  If that's what you want then use it, but I'm perplexed at why you'd be reading a book like Understand Exposure.  Spot metering is the mode for people who want total control over exposure.  However, the problem with controlling exposure is that you have to actually do it...you have to be able to set the desired exposure if you want your images to come out right.  If you read the book you should get some idea of how to do this.
> 
> Just a note...there's no benefit to shooting in manual.  Manual is good for times when the meter doesn't work, as with astrophotography, long exposure photography, and certain types of flash photography.  But with modern auto mode functionality, if the meter works then manual mode is the wrong mode.  You'll get more from an auto mode.  Also, the shooting mode has nothing to with setting exposure or anything to do with the metering mode.  All techniques used to determine correct exposure are equally valid in Program mode as they are in manual mode.  It truly means nothing to be shooting in manual mode.



So, you're saying that while shooting a basketball game in a gym with less than desirable light, I would be better off in auto mode?  Mind you I need to freeze action.


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## minooo (Apr 8, 2012)

MATRIX has evolved very much. I believe soon it will be able to recognize faces and expose after them. I see that matrix mode guesses many conditions that in the past where wrong, like a small black subject on a bright background, or a white bride dress, etc. These were impossible images in auto, now it works almost every time. if the minilabs would use the same principle...


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## minooo (Apr 8, 2012)

Graystar said:


> Those shots were never impossible.  You simply had to do what you would do in manual mode...compensate your exposure.


I am talking about the camera on its own metering. The new cameras, since D90, I noticed that just do the job out of the box, no compensation.

As about face detection, I am not talking about live view, but viewfinder metering and exposure. Maybe you are right, I just detailed for better understanding.


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## Compaq (Apr 8, 2012)

> And what I'm saying is that there is no need to "step out of auto mode" to "understand the 'why'". Manual mode offers no more help in understanding exposure than A, S, or P.




By writing this, you've forced me out of the couch, where I was lying extremely comfortably and reading this thread on my phone. 


Saying that M has no advantage in understanding exposure over A is, imo, stupid. Of course, I, nor you, can speak for all people and how they learn. Let me try to explain how I would start all over again - and how I urge people to start.

The first thing I would suggest, would be to read about shutter speed, aperture and ISO. Having a lens where one could actually see the diaphragms move, having an old film SLR without lens to actually see through the body and see how the shutter speed works. As for understanding ISO, film would, imo, be a very, very good way to start. Film sens and sensor sens are two different things, yet the same. I think it's easier for a beginner to understand that chemical reactions happen at a quicker rate when bla bla bla. 

If this is done properly, then exposure would be pretty straight forward. Certain surfaces reflect more light than others, and thus require less light to be rendered "as the eye see it". In a scene with direct sunlight and open shade, you might expose for the sunlight. If the mentioned principles are understood, it does not take a lot of brainpower to understand that in order to expose for the shadows, you'd need "more light", because the shadow is darker.

Once you're able to analyse your surroundings like that, you will be able to, with some experience, to see where  you should meter from to correctly expose for your subject, whether your subject is the sky, person in open shade, the stars, the moon, the space right next to the setting sun in order to not get a sun with really dark space around. This is all ambient light exposures, flash is an element that takes more practice.

Exposure isn't a hard thing to understand, but it's easy to "let the camera do the work" and not even think about what's really going on in the scene. By shooting in manual mode and using spot meter mode, it's easy to expose for different parts of the image, each requiring different amounts of light. You may take a reading off of a tree in shade, adjust settings and look at them. Then, take a reading off of a person's face in direct sunlight. Before doing anything, you should try to estimate the new exposure. See if you were going in the right direction. Auto would do the same, but I, personally, would prefer to actually turn the dials to change the exposure. *Even better*, get an old SLR or an old rangefinder with an aperture ringson the lens. Shooting film in full manual mode, with a pretty simple meter (compared to today's), would be the ultimate learning experience with regard to exposure (as well as composition, for that matter), imo.

Taking a class or having formal education is not necessary to understand exposure. Exposure is the *EASY *part of photography. It's how to compose shots, using exposure and elements of visual design to convey your message that's the hard part. It's never been easier to get properly exposed shots, what, with today's cameras doing it for you. With film, there is more to the process than just clicking. Actually developing the film and printing the negative each require experience to bring the most out of your initial exposure. But understanding the principles is easier with film, IMO. In some extent, I've started learning exposure all over again when started using a film camera.

(not checked for typos)


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## table1349 (Apr 8, 2012)

What a Crock. 

Perhaps YOU should learn what an exposure value is derived from.  Exposure Values are numbers which refer to certain combinations of lens aperture and shutter speed.  The combination of the these can provide the same value with different combinations of shutter speed and aperture.  Using program mode lets the camera choose the EV whether it is the right one or not.  Once you learn and understand the Exposure Triangle you then understand Exposure Values.  

Below is an Exposure Value Chart:







      Trying to understand EV without the understanding of the Exposure Triangle is like trying to drive a car without learning the rules of the road and laws of operating a motor vehicle.   Using P mode is like having your mom drive you and your date to Prom.


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## Compaq (Apr 8, 2012)

Graystar said:


> Compaq said:
> 
> 
> > Exposure isn't a hard thing to understand, but it's easy to "let the camera do the work" and not even think about what's really going on in the scene. By shooting in manual mode and using spot meter mode, it's easy to expose for different parts of the image, each requiring different amounts of light.
> ...




I agree that ISO should be kept for last. When I said "different amounts of light", things went a little fast. "Less of an exposure" might be what I meant, though that's a poor term. I agree that, for example

f/8
1/200th of a second

will bring in the same amount of light as

f/22
2 seconds

IF, and only if, the scenes are both rendered exactly the same. However, that situation would greatly depend on the scene, and any little thing the camera does with the information would ruin the experiment. It takes a certain amount of light to "properly" expose the medium at a given ISO to render a certain part of the scene certain way.

Give one film camera to a man, and another to a woman. Let's assume both cameras are identical, and both loaded with exactly the same film. They venture out to take a picture. Let's assume their meters are identical and dead accurate.

Man: exposes perfectly for something in open shade.
Woman: exposes perfectly for something in direct sunlight.

These two persons have now captured the same amount of light. However, they have used completely different settings on their camera. Reflected light intensity would vary depending on their subjects, but in the end the "same amount of light" was needed for both exposures, even if the exposures themselves were different. I know little of what light is measured in, there are several ways of doing it. Someone might be able to answer that.

Anyway, THAT is my basic understanding of how light works in photography. I think it's easier understood with film, but that's just me. Also, please keep in mind that I, in no way, have a deep understanding of light and exposure in the way that film/sensor/lens designers have. But I believe the principles are correct. When I said that exposure was the simple part in photography, I meant exposing an image "properly", not necessarily the principles behind it.


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## Helen B (Apr 8, 2012)

I don't see a lot of difference between Graystar's overridden auto metering and manual metering (except that full manual is often easier, faster and more consistent than overridden auto, especially when the light stays the same) . If you spot meter in auto then use exposure lock, one could consider that to be more like manual metering than auto. In many cases doing that once in manual works for the series of pictures, while with some cameras you would need to do that little ritual for each picture. If you use exposure compensation you may as well have used manual metering. The difference seems to be more one of fine semantics rather than it is of practicality.

By the way, APEX is a logarithmic system, it doesn't 'replace logarithmic', and you don't need two suns in the sky to require an EV100 over 16-1/3.


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## table1349 (Apr 8, 2012)

> QUOTE=Graystar;2557422]
> EV is much more than that.



No Exposure value is just that.  Exposure Value.  The physics of Exposure Value did not magically change because of digital cameras or some engineer that wrote a paper describing a new system of determining exposure. From your own wiki source: "In photography, *exposure value* (*EV*) denotes all combinations of a camera's shutter speed and relative aperture that give the same exposure."  That is Exposure Value, plain and simple.  Here is the formula for EV if you would like it. 







> Exposure Value comes from APEX...the Additive system of Photographic EXposure.  APEX converted the logarithmic system of determining exposure into a simple additive system.  Exposure Value has two meanings.  First, it is a combination of Aperture and Shutter.  Call that EV-C for the camera's exposure value.  Second, it's a combination of luminance (or illuminance) and the sensitivity.  Call that EV-S for the scene's exposure value.  When the EV-C equals the EV-S, you have standard exposure.  This is what cameras do today.
> 
> When in manual mode, the center of the Exposure Display represents the current EV of the scene.  When you apply Exposure Compensation you're biasing the EV of the scene, which causes the camera to adjust the EV of the camera.  Everything in the camera runs on this relationship of EV-C to EV-S.
> 
> ...



NO. Exposure value has been around long before 2007 when Douglas Kerr wrote a paper on the APEX system.  I learned exposure value back in the 1970's. The physics of Exposure Value was the same before then and hasn't changed since.   APEX incorporates EV as part of the method of determining proper exposure in that system.  



> You're only saying that because you don't understand how auto modes operate.  You have just as much control over exposure in P mode as you do in M mode.  If you knew how auto modes worked, you'd agree.



No I am saying this because I am a photographer.  The auto mode does not know or understand what I the photographer consider the proper exposure for what I am trying to capture and convey.  



> It's nothing like that at all...obviously...since APEX was a system used to determine exposure and ISO is on the other side of the equal sign.  You need to complete your understanding of EV by reading the links above.



So make up your mind, are you talking about EV or APEX?  They are not the same and I understand EV.    



> Again, you say that because you don't understand how the auto modes work, or how to used them on a modern camera.



Tell you what, lets meet on the sideline at say OSU this year and I will shoot manual as I always do and you shoot in P mode or even better, I will let you use Sports mode if your camera has such, and lets see who freezes the action while capturing only the action in sharp focus with a correct exposure for the people involved in the action.  Haven't found a camera yet that you can stick in P mode and stand there and get a useable shot in such situations.  

But then I also understand how an automatic transmission works, but have yet to see Formula 1, Indy, Nascar, or NHRA sticking them in their machines.  Wonder why?


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## Helen B (Apr 8, 2012)

Graystar said:


> Manual mode tends to put a damper on experimentation because fluidity is broken by having to manage exposure.  So people just pick one aperture and one shutter for the light and shoot everything with that.



Well that's plain nonsense, and it ignores the history and practice of photography before auto metering. Your fluidity might be broken, but that's you, not the system. I suspect that we'll just have to disagree on this, because discussion seems pointless.




> To go from 14 2/3 EV to 15 2/3 EV requires doubling the light.  You'd need a second sun to have a standard exposure at 15 2/3 EV.



No you wouldn't. First, you are misusing the system you claim to know about. You can go way above a standard exposure of EV 15 in full sun - it simply needs a sensitivity higher than ISO 100. I suspect, however, that you really mean EV100 (EV at ISO 100, or BV +5).

In full sun with clear sky it isn't impossible to have a standard exposure of a standard subject (ie 14% reflectivity or thereabouts) of EV100 15. (1/125 at f/16 and ISO 100) For the sake of argument we'll lower that to the exact Sunny 16 rule of EV100 14-2/3. That means that a matrix meter segment could be measuring a bright white value that is around EV100 17, which it will not add into the exposure evaluation because it is considered by the guys who designed the system to be correctly represented as featureless highlight. In a backlit scene the meter can be trying to read values well over EV100 17 - even backlit blacktop has an EV100 of over 17. This cannot be assumed to be properly represented as detailless highlight, so the user would have to compensate because the scene is outside the range the matrix system was designed for (however good it is in other circumstances). You don't need two suns, you just need to go outside a rather limited range of reflectivity in full sun.


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## Helen B (Apr 9, 2012)

Graystar said:


> But you're missing the point that even if you are reading 17 EV off of snow, the correct exposure is still 14 2/3 EV. To have a correct exposure of 15 2/3 EV, you'd need two suns in the sky.



I didn't mention snow, but never mind, and I didn't miss that point - it is a rather basic one that I would expect most experienced photographers to take for granted.  You seem to have your blinkers on, and not thinking about this because you can't see how the correct exposure can be above EV100 14-2/3 without there being 'two suns in the sky' - you seem fixated on that notion (and you are still using EV incorrectly). I'm referring to situations in which the 'correct' exposure is above EV100 14-2/3, but the important thing is the way matrix metering works (or more correctly, doesn't work) for high values. I think that you are misunderstanding how matrix metering works. The limit on assumed maximum reflectivity is a simplification in the system that was made so that it works well for the vast majority of situations, but that causes it to fall down in a few situations.


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## Helen B (Apr 10, 2012)

I can't see much point to further discussion. We'll just have to disagree if you can't understand why an exposure in natural daylight can be over EV100 14-2/3. My experience tells me otherwise.


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## Jeff92 (Apr 20, 2012)

To put the OP's question back in the light, I am in the process of reading Understand Exposure as well.  I only have like 20 pages left but the whole book kept me thinking, what type of metering is he using?  It isn't until around page 120 or so, maybe higher, that he starts talking about what he is metering.  He says that spot metering is sometimes appropriate but often inaccurate.  I interpreted his metering section as he is using partial metering tbh.  My question is this I guess.  When he meters to the sky, does he take a spot meter to the part of the sky he wants, does he partial meter a small area of the sky, or does he evaluatively meter the entire sky which seems like it wouldn't work as he often states he uses a wide angle lens, that would of course be impossible to grab just part of the sky above the landscape in order to achieve correct exposure, so he must use spot metering...? 

Here is the exact quote, "My feelings about spot meters haven't changed that much since I first learned of them over twenty-five years ago: they have a limited but important use in my daily picture-taking efforts."


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## Jeff92 (Apr 20, 2012)

Also, it is never safe to assume which ISO he uses which is also troubling.  I guess using the skills he teaches in the book, that is for me to determine myself


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## MTVision (Apr 20, 2012)

Jeff92 said:
			
		

> Also, it is never safe to assume which ISO he uses which is also troubling.  I guess using the skills he teaches in the book, that is for me to determine myself



It's been a while since I read that book but...I'm betting he says to use the lowest ISO possible. And in some of the exercises I believe he does tell you to set your ISO to 200. 

For the metering off the sky - maybe I assumed a little but I took it that he spot metered of the sky.


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## DScience (Apr 20, 2012)

Crollo said:
			
		

> I really don't understand what you're trying to figure out here... With a scene that does not exceed the dynamic range of your medium, it doesn't matter. If your scene exceeds the dynamic range of your medium, then you figure it out. We can't decide for you what should be exposed in YOUR image. Is the terrain in your scene the dominant subject, or is the sky the dominant subject in the scene? Expose for what you want to be exposed and blow out or crush the other... Simple.



Bro, he didn't even know what it meant to meter off the sky, let alone meter of anything else! You're several steps ahead of him...


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## Bitter Jeweler (Apr 20, 2012)

Where did Graystar's posts go? I hate F'd up continuity!


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## Jeff92 (Apr 20, 2012)

MTVision said:


> Jeff92 said:
> 
> 
> 
> ...



Yeah I skipped around the last pages and noticed that he did mention once that 99% of the time he is shooting at 100-200 iso, so there is my answer, and for anyone else wondering.  That was the first book I have read in years it seems like.  It was really interesting.  I feel like I know my camera a lot better now.  Now I just have to put it to practice


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## table1349 (Apr 21, 2012)

Bitter Jeweler said:


> Where did Graystar's posts go? I hate F'd up continuity!


 I think he took his ball and went home after deleating his posts.


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