What is metering?

HAPPYGUY_45 · May 17, 2023

be nice Hello im over the iso/F#/SS hump and learning my way around my camera. My new question is metering. Does this have to do with exposure? I have it on multi all the time. I watched a you tube and the person went into spot metering where he would take a picture than take a picture of what he wanted to. What does this do?

IS MULTI METERING GOOD?

so what i do is get my my ss right aperture and iso as low as posible then my dial on exposure is at 0 then i take picture.

THis this correct or is underexp or over ex good i cant see howit would be but im new

thanks

JustUs7 · May 17, 2023

Metering is just the camera measuring light coming off the scene. Evaluative or multi measures the whole sensor. Spot measure just a small area. For some cameras it meters the focus point. For others it’s just a spot in the middle. Good for properly exposing a subject in tricky light. Like a bird against a bright sky. Maybe you’ll lose the sky (overexposed), but you’ll see the bird. There’s also center weighted and other methods.

So in short, metering is the camera measuring the light to recommend exposure.

Metering to 0 shouldn’t necessarily be the goal. Because the camera wants to meter to a neutral brightness. Usually 18% grey. Both of the images below were taken at f/2 and 1/125th shutter speed using auto iso.

This is a white piece of paper metered to 0 using auto iso.

This is a black piece of paper metered to 0 using auto iso.

In the case of a light scene that you want to appear light, you may have to bias the meter. So +1 or +2 on the meter might actually be more accurate. Consider a snowy scene where you want white snow.

This is +1 2/3rds because the snow would have all been dull grey and everything gloomier if I had targeted 0.

Or in dark rides. This is -1 1/3rd. Had I targeted 0 it would be too bright. Noise would be more evident. It wouldn’t have accurately represented the scene as I saw it.

You’re better served watching your histogram than you are targeting 0 on your meter.

Oh. The pieces of paper from above metered to +2 and -2 respectively.

Tom_N · May 17, 2023

HAPPYGUY_45 said:
be nice Hello im over the iso/F#/SS hump and learning my way around my camera. My new question is metering. Does this have to do with exposure? I have it on multi all the time. I watched a you tube and the person went into spot metering where he would take a picture than take a picture of what he wanted to. What does this do?

Metering is the process of estimating how much light is falling on a scene, so that you can set a "correct" combination of

exposure parameters (aperture, shutter speed)
lightness parameters (ISO)

to get a good photo.

All modern DSLR and mirrorless cameras have built-in light meters, but these meters are reflective (that is, they measure how much light bounces off a subject, as opposed to how much light falls on a subject). A subject such as a white wedding dress or a black cat that reflects much more, or much less, light than a "neutral gray" card may fool the meter.

This is part of the reason why there are multiple metering modes and why there is even a manual override (exposure compensation dial).

HAPPYGUY_45 said:
IS MULTI METERING GOOD?

Multi-metering tries to estimate lighting based on many samples. The camera compares these samples to a database built in by the camera manufacturer, in hopes of improved accuracy.

HAPPYGUY_45 said:
so what i do is get my my ss right aperture and iso as low as posible then my dial on exposure is at 0 then i take picture.

The exposure compensation dial lets you bias the meter reading. Most of the time, you would leave it set to 0, but this in and of itself does not guarantee that you have picked a "correct" (shutter speed, aperture, ISO) combination.

In many metering modes, the camera "works to the meter" and it will try to automatically pick one or two of the parameters to make the picture come out right (if possible).

E.g., in Aperture priority (A/Av) mode,

You set the aperture
The camera sets the shutter speed
The camera may also set the ISO (if Auto-ISO is enabled)

If you are in a dark room and you set a very small aperture (like f/11), the camera might not be able to set a shutter speed high enough to control motion blur and hand shake. The various metering modes are a convenience; they let you focus on the thing that you want to control, but there's still going to be a tradeoff of parameters that depends upon the available light.

HAPPYGUY_45 said:
THis this correct or is underexp or over ex good i cant see howit would be but im new

thanks

HAPPYGUY_45 · May 17, 2023

JustUs7 said:
Metering is just the camera measuring light coming off the scene. Evaluative or multi measures the whole sensor. Spot measure just a small area. For some cameras it meters the focus point. For others it’s just a spot in the middle. Good for properly exposing a subject in tricky light. Like a bird against a bright sky. Maybe you’ll lose the sky (overexposed), but you’ll see the bird. There’s also center weighted and other methods.

So in short, metering is the camera measuring the light to recommend exposure.

Metering to 0 shouldn’t necessarily be the goal. Because the camera wants to meter to a neutral brightness. Usually 18% grey. Both of the images below were taken at f/2 and 1/125th shutter speed using auto iso.

This is a white piece of paper metered to 0 using auto iso.

This is a black piece of paper metered to 0 using auto iso.

In the case of a light scene that you want to appear light, you may have to bias the meter. So +1 or +2 on the meter might actually be more accurate. Consider a snowy scene where you want white snow.

This is +1 2/3rds because the snow would have all been dull grey and everything gloomier if I had targeted 0.

Or in dark rides. This is -1 1/3rd. Had I targeted 0 it would be too bright. Noise would be more evident. It wouldn’t have accurately represented the scene as I saw it.

You’re better served watching your histogram than you are targeting 0 on your meter.

Oh. The pieces of paper from above metered to +2 and -2 respectively.

thanks for the example. I don't really get metering 100% i get what the cameras is doing. There is times like now i don't wanna take pictures of birds in sky cause its a nightmare to edit. Water also another nightmare. Glare etc. So metering helps with that? interesting.

Exposure i get right away. Ill keep that in mind and go out tomorrow and use the histogram. I used to use it a lot. Then forgot about it i guess.

ty

JustUs7 · May 17, 2023

Glare off water is helped by a circular polarizing filter (a CPL).

alcelc · May 17, 2023

Might I bookmark it, or even copy the entire writing plus samples (if allowed) for future uses?

NicholasD · May 18, 2023

HAPPYGUY_45 said:
JustUs7 said:

Metering is just the camera measuring light coming off the scene. Evaluative or multi measures the whole sensor. Spot measure just a small area. For some cameras it meters the focus point. For others it’s just a spot in the middle. Good for properly exposing a subject in tricky light. Like a bird against a bright sky. Maybe you’ll lose the sky (overexposed), but you’ll see the bird. There’s also center weighted and other methods.

So in short, metering is the camera measuring the light to recommend exposure.

Metering to 0 shouldn’t necessarily be the goal. Because the camera wants to meter to a neutral brightness. Usually 18% grey. Both of the images below were taken at f/2 and 1/125th shutter speed using auto iso.

This is a white piece of paper metered to 0 using auto iso.

This is a black piece of paper metered to 0 using auto iso.

In the case of a light scene that you want to appear light, you may have to bias the meter. So +1 or +2 on the meter might actually be more accurate. Consider a snowy scene where you want white snow.

This is +1 2/3rds because the snow would have all been dull grey and everything gloomier if I had targeted 0.

Or in dark rides. This is -1 1/3rd. Had I targeted 0 it would be too bright. Noise would be more evident. It wouldn’t have accurately represented the scene as I saw it.

You’re better served watching your histogram than you are targeting 0 on your meter.

Oh. The pieces of paper from above metered to +2 and -2 respectively.

Click to expand...

thanks for the example. I don't really get metering 100% i get what the cameras is doing. There is times like now i don't wanna take pictures of birds in sky cause its a nightmare to edit. Water also another nightmare. Glare etc. So metering helps with that? interesting.

Exposure i get right away. Ill keep that in mind and go out tomorrow and use the histogram. I used to use it a lot. Then forgot about it i guess.

ty

One important thing to note is that while the camera mfg's metering algorithms are very sophisticated and precise, they are not perfect and can't nail every situation "perfectly". Add to that, the subjective nature of each person's artistic intent. That's why there is exposure compensation. I would take the time to understand metering systems and why multi/matrix/evaluative is preferred over spot in certain situations (and vice versa) as per the above, but I would I give yourself plenty of latitude to use the EC dial whenever and as much as needed. Doing that will help make you a better photographer.

As far as glare on water and birds in flight, that's a whole different problem (glare - shoot RAW and tone down the highlights. BIF - bright days - use positive EC to expose for the bird at the expense of the sky. Take a few practice shots at +0.7 or +1.0 EC and see what that does. Yeah, the sky might have some blinks, but big deal. If the sky is properly exposed, that small bird is going to be fairly dark and when you go to increase shadows or darks, you'll end up with a noisy mess)

In my view, the best answer to all of the above is to practice, practice, practice. Results will come.

JustUs7 · May 18, 2023

alcelc said:
Might I bookmark it, or even copy the entire writing plus samples (if allowed) for future uses?

HAPPYGUY_45 · May 18, 2023

JustUs7 said:
Glare off water is helped by a circular polarizing filter (a CPL).

thank you. So its not just me lol

HAPPYGUY_45 · May 18, 2023

NicholasD said:
HAPPYGUY_45 said:

JustUs7 said:

Metering is just the camera measuring light coming off the scene. Evaluative or multi measures the whole sensor. Spot measure just a small area. For some cameras it meters the focus point. For others it’s just a spot in the middle. Good for properly exposing a subject in tricky light. Like a bird against a bright sky. Maybe you’ll lose the sky (overexposed), but you’ll see the bird. There’s also center weighted and other methods.

So in short, metering is the camera measuring the light to recommend exposure.

Metering to 0 shouldn’t necessarily be the goal. Because the camera wants to meter to a neutral brightness. Usually 18% grey. Both of the images below were taken at f/2 and 1/125th shutter speed using auto iso.

This is a white piece of paper metered to 0 using auto iso.

This is a black piece of paper metered to 0 using auto iso.

In the case of a light scene that you want to appear light, you may have to bias the meter. So +1 or +2 on the meter might actually be more accurate. Consider a snowy scene where you want white snow.

This is +1 2/3rds because the snow would have all been dull grey and everything gloomier if I had targeted 0.

Or in dark rides. This is -1 1/3rd. Had I targeted 0 it would be too bright. Noise would be more evident. It wouldn’t have accurately represented the scene as I saw it.

You’re better served watching your histogram than you are targeting 0 on your meter.

Oh. The pieces of paper from above metered to +2 and -2 respectively.

Click to expand...

thanks for the example. I don't really get metering 100% i get what the cameras is doing. There is times like now i don't wanna take pictures of birds in sky cause its a nightmare to edit. Water also another nightmare. Glare etc. So metering helps with that? interesting.

Exposure i get right away. Ill keep that in mind and go out tomorrow and use the histogram. I used to use it a lot. Then forgot about it i guess.

ty

Click to expand...

One important thing to note is that while the camera mfg's metering algorithms are very sophisticated and precise, they are not perfect and can't nail every situation "perfectly". Add to that, the subjective nature of each person's artistic intent. That's why there is exposure compensation. I would take the time to understand metering systems and why multi/matrix/evaluative is preferred over spot in certain situations (and vice versa) as per the above, but I would I give yourself plenty of latitude to use the EC dial whenever and as much as needed. Doing that will help make you a better photographer.

As far as glare on water and birds in flight, that's a whole different problem (glare - shoot RAW and tone down the highlights. BIF - bright days - use positive EC to expose for the bird at the expense of the sky. Take a few practice shots at +0.7 or +1.0 EC and see what that does. Yeah, the sky might have some blinks, but big deal. If the sky is properly exposed, that small bird is going to be fairly dark and when you go to increase shadows or darks, you'll end up with a noisy mess)

In my view, the best answer to all of the above is to practice, practice, practice. Results will come.

you read my mind on the noisy mess. Im in no hurry i can see myself taking pictures forever. Just wanna be the best that i can be

Bill Ferris · May 19, 2023

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Why is this important? Suppose you compose a photo of a scene, select f/8, 1/100, ISO 200 for settings, and the meter reading is 0. If you change the shutter speed to 1/3200 and increase ISO to 6400, you'll get the same meter reading of 0. Exposure will have been reduced by 5 stops but the meter reading will be unchanged. The in-camear meter is not an exposure (brightness) meter; it's a lightness meter.

So, what does a meter reading of 0 mean? It's the camera telling you that the photo about to be made will have the same tonality - the same tonal lightness - as middle gray or 18% gray. A meter reading of +2 stops indicates the JPEG will have the same lightness as a snow-covered field. A meter reading of -2 stops forecasts a photo having the same tonality as a black tuxedo.

The in-camera meter is a scale ranging from -3 or -2 stops to +2 or +3 stops. The reading is the camera's prediction of the lightness a JPEG will have in that light at the chosen f-stop, shutter speed, and ISO. With 0 being at the middle of the scale, it's the reference and a reading of 0 represents a photo having an overall lightness matching that of middle gray.

If you do photography with a mirrorless camera, I'd recommend giving more weight to the appearance of the composition in the electronic viewfinder (EVF) than to the meter reading displayed. If the scene has a pleasing lightness to your eye, that's a good start. If you've selected the widest aperture delivering a sufficient depth of field and the slowest shutter speed that adequately freezes any movement in the frame, you're working with an optimal exposure.

If you do photography with a DSLR, the appearance of the scene in the optical viewfinder doesn't necessarily match or even indicate the lightness the resulting photo will have. This is where the in-camera meter is a useful reference. Does the reading match the natural lightness of the scene? If not, what options do you have to alter settings to produce a photo that looks more natural?

When shooting in manual exposure, you have control over f-stop and shutter speed. If also manually controlling ISO, you have total control over the settings that, along with scene brightness, dictate the in-camera meter reading.

If you use one of the camera's automated exposure modes, the exposure compensation tool comes into play. By design, a camera in an auto exposure mode will choose one or more settings to produce a meter reading of 0...to give the world a middle gray tonality. This is not necessarily bad. In many situations, the scene being photographed will incorporate a range of brightnesses from deep shadows to bright highlights. An overall middle gray lightness strikes a balance between those extremes.

However, there are times when the scene is not naturally middle of the road in overall lightness. A wintry scene with snow-covered fields is about 2 stops brighter. A landscape at twilight is much darker. Consider a white wedding dress, black tuxedo, white bird, or black bear...these are subjects that do not naturally look middle gray in lightness to the eye.

When using an auto exposure mode and photographing a scene or subject that does not appear middle gray in tonal lightness, exposure compensation (EC) is a tool the photographer can use to force the camera to choose settings that will produce a photo giving the composition a natural-looking tonality. If you set EC to +2, a photo of a snowy field will have a natural lightness. An EC of -2 will capture a black tuxedo with a natural lightness.

Any of the metering modes (multi/matrix, center-weighted, spot) can be used. The key is understanding what the resulting meter reading is telling you, That's a subject deserving of its own thread.

But the place to start, is to understand that the in-camera meter predicts the lightness a JPEG will have in the available light at the chosen settings. A meter reading of 0 is no more or less correct than any other meter reading. A reading of 0 merely indicates that the resulting photo's overall lightness will match that of middle gray. Whether or not that's the reading you want depends on the natural tonality of the scene and, of course, on your personal aesthetic. Are you trying to make a photo that captures the scene as it appears to the eye?

Alfn2 · May 19, 2023

Bill Ferris said:
In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Tom_N · May 19, 2023

Alfn2 said:
Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

There may be several exposures that result in reproducing a mid-grey object as mid-grey.

Given constant illumination, (f/8, 1/240th second) results in only 1/16th the exposure of (f/4, 1/60th second). If you use ISO 1600 for the photo with the small exposure, and ISO 100 for the photo with the large exposure, mid-greys should come out about the same. (The photo taken with the small exposure may be much noisier.)

Thus what the metering system is doing is generally not determining optimal exposure, but determining (exposure + lightness adjustment).

JustUs7 · May 19, 2023

Alfn2 said:
Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Bill is quite correct. My two grey images above were identical in exposure. Same scene luminosity, same aperture, same shutter speed. They only both appear grey because the ISO changed the lightness of the image. But that’s if you accept the traditional definition of exposure, which iso is not a part of, but rather a mitigating lightness control.

But if we go down that road, this thread will hit 150 real quick and be boring as any of the other million times it’s been discussed here.

Bill Ferris · May 19, 2023

Alfn2 said:
Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

This outta be fun.

Alfn2 said:
[Irrelevant trip down memory lane about the days of film photography deleted.]

The topic is in-camera metering.

Alfn2 said:
Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

That's an interesting fairy tale. Here's how in-camera metering really works. The first photo shows the in-camera meter reading (0.0) and histogram for the ambient light and settings chosen. Those settings are f/4.0, 1/2.5, and ISO 200.

The second photo shows the in-camera meter reading and histogram for the exact same composition in the exact same light at very different settings: The new settings are f/4.0, 1/80, and ISO 6400.

The second photo uses an exposure reduced by 5 stops in comparison with the first. Yet the in-camera meter and histogram are identical.

As explained in my earlier post, the in-camera meter is a lightness meter. If predicts the lightness of the JPEG about to be made at the chosen exposure and ISO settings. It does not indicate exposure, a fact that is irrefutably demonstrated by the identical readings produced by wildly different exposures.

While we're on the subject, the histogram also is not an indicator of exposure. It also takes ISO into account, which makes its function that of mapping the distribution of pixels across a range of lightnesses from black to white.

--
Bill Ferris Photography
Flagstaff, AZ

http://www.billferris.photoshelter.com

Bill Ferris · May 19, 2023

Tom_N said:
Alfn2 said:

Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Click to expand...

There may be several exposures that result in reproducing a mid-grey object as mid-grey.

Given constant illumination, (f/8, 1/240th second) results in only 1/16th the exposure of (f/4, 1/60th second). If you use ISO 1600 for the photo with the small exposure, and ISO 100 for the photo with the large exposure, mid-greys should come out about the same. (The photo taken with the small exposure may be much noisier.)

Thus what the metering system is doing is generally not determining optimal exposure, but determining (exposure + lightness adjustment).

As already explained, it's a lightness meter.

HAPPYGUY_45 · May 19, 2023

Bill Ferris said:
Alfn2 said:

Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Click to expand...

This outta be fun.

Bill Ferris said:

[Irrelevant trip down memory lane about the days of film photography deleted.]

Click to expand...

The topic is in-camera metering.

Bill Ferris said:

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Click to expand...

That's an interesting fairy tale. Here's how in-camera metering really works. The first photo shows the in-camera meter reading (0.0) and histogram for the ambient light and settings chosen. Those settings are f/4.0, 1/2.5, and ISO 200.

The second photo shows the in-camera meter reading and histogram for the exact same composition in the exact same light at very different settings: The new settings are f/4.0, 1/80, and ISO 6400.

The second photo uses an exposure reduced by 5 stops in comparison with the first. Yet the in-camera meter and histogram are identical.

As explained in my earlier post, the in-camera meter is a lightness meter. If predicts the lightness of the JPEG about to be made at the chosen exposure and ISO settings. It does not indicate exposure, a fact that is irrefutably demonstrated by the identical readings produced by wildly different exposures.

While we're on the subject, the histogram also is not an indicator of exposure. It also takes ISO into account, which makes its function that of mapping the distribution of pixels across a range of lightnesses from black to white.

Wow I'm confused which is ok. All apart of the learning. Bill hot damn you got some impressive photos.

Alfn2 · May 20, 2023

Tom_N said:
Alfn2 said:

Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Click to expand...

There may be several exposures that result in reproducing a mid-grey object as mid-grey.

Given constant illumination, (f/8, 1/240th second) results in only 1/16th the exposure of (f/4, 1/60th second). If you use ISO 1600 for the photo with the small exposure, and ISO 100 for the photo with the large exposure, mid-greys should come out about the same. (The photo taken with the small exposure may be much noisier.)

Thus what the metering system is doing is generally not determining optimal exposure, but determining (exposure + lightness adjustment).

I should have said; the optimal exposure for any given ISO sensitivity setting or, if you prefer, the optimal exposure and auto-ISO sensitivity setting.

Incidentally, ISO12232:2019 describes the ISO setting as setting the effective sensitivity of the digital stills camera (DSC) in a similar manner to the ISO setting on film cameras or hand-held exposure meters. Nowhere does it refer to it as a lightness control. In fact, they go to some pains to emphasis that it is intended to mimic the ISO speed setting on a film camera.

That is why hand-held exposure meters, old or new, can be used with both film and digital cameras.

Alfn2 · May 20, 2023

JustUs7 said:
Alfn2 said:

Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Click to expand...

Bill is quite correct. My two grey images above were identical in exposure. Same scene luminosity, same aperture, same shutter speed. They only both appear grey because the ISO changed the lightness of the image. But that’s if you accept the traditional definition of exposure, which iso is not a part of, but rather a mitigating lightness control.

But if we go down that road, this thread will hit 150 real quick and be boring as any of the other million times it’s been discussed here.

I disagree. Bill is quite wrong to say In-camera metering forecasts the lightness of the photo about to be made. That defies all logic.

I would otherwise refer you to my answer to Tom_N.

Alfn2 · May 20, 2023

Bill Ferris said:
Tom_N said:

Alfn2 said:

Bill Ferris said:

In-camera metering forecasts the lightness of the photo about to be made. I say, lightness, because metering takes scene brightness, f-stop, shutter speed, and ISO into account. With ISO as a factor, the meter isn't strictly an exposure indicator. If it were, we would be talking about metering being an indicator of brightness; the light used to make a photo. However, ISO brings post-exposure processing into play and that makes the in-camera meter an indicator of the lightness of the JPEG about to be made.

Click to expand...

I don't know where you got this explanation from but it is totally wrong.

Metering is how your camera evaluates the light of a scene to determine the correct shutter speed, aperture, or ISO. Back in the old days of photography, cameras were not equipped with a light “meter”, which is a sensor that measures the amount and intensity of light. Photographers had to use hand-held light meters to determine the optimal exposure. Obviously, because the work was shot on film, they could not preview or see the results immediately, which is why they religiously relied on those light meters.

Today, every digital camera has an integrated light meter that automatically measures the reflected light and determines the optimal exposure. The optimal exposure being one that ensures that a mid-grey object is reproduced as mid-grey.

You will find further details in any good book on photography.

Click to expand...

There may be several exposures that result in reproducing a mid-grey object as mid-grey.

Given constant illumination, (f/8, 1/240th second) results in only 1/16th the exposure of (f/4, 1/60th second). If you use ISO 1600 for the photo with the small exposure, and ISO 100 for the photo with the large exposure, mid-greys should come out about the same. (The photo taken with the small exposure may be much noisier.)

Thus what the metering system is doing is generally not determining optimal exposure, but determining (exposure + lightness adjustment).

Click to expand...

As already explained, it's a lightness meter.

Not according to ISO12232:2019. And the ISO should know.

What is metering?

Forum Enthusiast

Veteran Member

Forum Pro

Forum Enthusiast

Veteran Member

Forum Pro

Senior Member

Veteran Member

Forum Enthusiast

Forum Enthusiast

Community Leader

Well-known member

Forum Pro

Veteran Member

Community Leader

Community Leader

Forum Enthusiast

Well-known member

Well-known member

Well-known member

Similar threads

Keyboard shortcuts