Correct Exposure

Hello all,

New to the site; first time posting.

I have a canon 30d. I am also in the process I learning photography. In reading some books talking about exposure, there is a statement that I come across that is a bit confusing.

"correct exposure"

Example:

- Set mode to manual
- set lens opening to f/5.6
- adjust the shutter speed until the camera's light meter indicates a correct exposure.

The part that is confusing me is the last step. What in the camera is going to tell me that I have the correct exposure?

Umm, I'm no expert either, infact far from it, but theres a meter on your camera, it usually runs -2 to 2 and when you're at 0, you got the correct exposure.

I also think theres different ways to measure the exposure.

Hi, Joe, and welcome to the forum.

I'd guess the book you are reading is "Understanding Exposure", as that style of writing seems all too familiar. I'm afraid the correct answer is not simple. A camera's meter has no idea what sort of subject/scene you are pointing it at and it has no idea whether it should be dark or light or somewhere in the middle. All that the camera can do is to indicate an exposure that will average out the metered part of the scene to a "middle tone", often referred to as "middle grey". The skill of the photographer is in knowing how much darker or brighter than "middle grey" the thing being metered should actually be. e.g. a dark suit might be a couple of stops darker than middle grey. A white wedding dress or snow might be a couple of stops above middle grey. Untanned caucasian skin might be about 1 stop above middle grey. Green grass might be between -1 stop below middle grey or even about equal to middle grey.

So while it is true that the meter can indicate when you have a correct exposure, it is far from correct to assume that a centred meter reading is the correct value. You, the photographer, need to understand where on the scale the meter should be in order to indicate a correct exposure. This is one area in which I think "Understanding Exposure" fails significantly. Bryan keeps going on about the "correct exposure" without telling you how to interpret it correctly. I don't know whether this will help but imagine a car speedometer. It will tell you how fast you are going, but not whether your speed is suitable for the road and weather conditions. You have to figure out the "correct" speed. The camera meter is much the same. It indicates how bright your exposure is, relative to middle grey, but not whether that is the correct exposure for the scene.

When you meter a whole scene, with a broad range of tones, can you tell whether the scene as a whole is about "average", or brighter or darker than "average", and if so, by how much? Well even with some experience I still find that requires a bit too much guesswork, so I like to narrow down the variables. I will normally use spot metering, so that I can concentrate the metered area to a small, distinct part of the scene and I will meter off something I think I can get a reliable reading from. A favourite is to meter off the palm of my hand and set the exposure to +1 1/3 stops. Another is to meter off grass, but I vary the meter setting for grass from between -1 stops to +0 stops depending on the content of the scene. If there are no bright areas within the scene then I will meter at +0 stops. However, if there is something bright and important to me, such as a white bird or dog, or person dressed in white, then I will meter off the grass at -1 stop. That approach will protect my highlights in a scene with bright parts, while capturing good shadow detail in a scene with no important highlight detail. Another option is to spot meter the brightest part of the scene (white cloud, wedding dress, snow) for which I want to retain visible detail and set my exposure so that the meter is at +2 stops (+3 stops if I'm shooting raw) for that part of the scene.

That's a short precis about interpreting the camera's meter. Another tool that is really valuable in digital photography, yet which gets no mention at all in "Understanding Exposure" is the camera's histogram and also the blinking highlight warnings you may see on the preview image on the back of the camera. You would do well to learn how to interpret the histogram as this is a crucial guide to showing the actual exposure you ended up with, after you've taken the shot. If you spot an exposure error you will hopefully have time to adjust the camera and take another shot. For more on understanding histograms, take a look here....

http://ronbigelow.com …gram/camera-histogram.htm

and

http://www.luminous-landscape.com …standing-histograms.shtml

aprofetto wrote in post #7865897
Umm, I'm no expert either, infact far from it, but theres a meter on your camera, it usually runs -2 to 2 and when you're at 0, you got the correct exposure.

I also think theres different ways to measure the exposure.

If you're shooting a snow bank and the meter is at O, you'll have an underexposed shot. If you're shooting a black cat that fills the frame and the meter is at 0, you'll have an overexposed shot. The O is a reference point and the photographer must know how to interpret when the exposure is right or not.

tdodd wrote in post #7866523
Hi, Joe, and welcome to the forum.

I'd guess the book you are reading is "Understanding Exposure", as that style of writing seems all too familiar. I'm afraid the correct answer is not simple. A camera's meter has no idea what sort of subject/scene you are pointing it at and it has no idea whether it should be dark or light or somewhere in the middle. All that the camera can do is to indicate an exposure that will average out the metered part of the scene to a "middle tone", often referred to as "middle grey". The skill of the photographer is in knowing how much darker or brighter than "middle grey" the thing being metered should actually be. e.g. a dark suit might be a couple of stops darker than middle grey. A white wedding dress or snow might be a couple of stops above middle grey. Untanned caucasian skin might be about 1 stop above middle grey. Green grass might be between -1 stop below middle grey or even about equal to middle grey.

So while it is true that the meter can indicate when you have a correct exposure, it is far from correct to assume that a centred meter reading is the correct value. You, the photographer, need to understand where on the scale the meter should be in order to indicate a correct exposure. This is one area in which I think "Understanding Exposure" fails significantly. Bryan keeps going on about the "correct exposure" without telling you how to interpret it correctly. I don't know whether this will help but imagine a car speedometer. It will tell you how fast you are going, but not whether your speed is suitable for the road and weather conditions. You have to figure out the "correct" speed. The camera meter is much the same. It indicates how bright your exposure is, relative to middle grey, but not whether that is the correct exposure for the scene.

When you meter a whole scene, with a broad range of tones, can you tell whether the scene as a whole is about "average", or brighter or darker than "average", and if so, by how much? Well even with some experience I still find that requires a bit too much guesswork, so I like to narrow down the variables. I will normally use spot metering, so that I can concentrate the metered area to a small, distinct part of the scene and I will meter off something I think I can get a reliable reading from. A favourite is to meter off the palm of my hand and set the exposure to +1 1/3 stops. Another is to meter off grass, but I vary the meter setting for grass from between -1 stops to +0 stops depending on the content of the scene. If there are no bright areas within the scene then I will meter at +0 stops. However, if there is something bright and important to me, such as a white bird or dog, or person dressed in white, then I will meter off the grass at -1 stop. That approach will protect my highlights in a scene with bright parts, while capturing good shadow detail in a scene with no important highlight detail. Another option is to spot meter the brightest part of the scene (white cloud, wedding dress, snow) for which I want to retain visible detail and set my exposure so that the meter is at +2 stops (+3 stops if I'm shooting raw) for that part of the scene.

That's a short precis about interpreting the camera's meter. Another tool that is really valuable in digital photography, yet which gets no mention at all in "Understanding Exposure" is the camera's histogram and also the blinking highlight warnings you may see on the preview image on the back of the camera. You would do well to learn how to interpret the histogram as this is a crucial guide to showing the actual exposure you ended up with, after you've taken the shot. If you spot an exposure error you will hopefully have time to adjust the camera and take another shot. For more on understanding histograms, take a look here....

http://ronbigelow.com …gram/camera-histogram.htm

and

http://www.luminous-landscape.com …standing-histograms.shtml

Hey Tim - Thanks for the detailed info. That is too funny that you knew the book I was reading. I like Bryans approach. From my perspective it has helped me with many things but as you mentioned there are some things either left out or not explained.

Also I would have to think that in conjunction with correct exposure would be setting the correct white balance. in playing with the settings the AWB doesn't seem to be the most accurate at times.

I try to view the histogram but don't have a clear understanding of what is telling me. I do know that too far left is basically dark and too far right is lighter.

I will be sure to read the links attached.

Thanks again!

Joe

gooble wrote in post #7866747
If you're shooting a snow bank and the meter is at O, you'll have an underexposed shot. If you're shooting a black cat that fills the frame and the meter is at 0, you'll have an overexposed shot. The O is a reference point and the photographer must know how to interpret when the exposure is right or not.

Like I said, I'm no expert... I still have lots to learn myself, thanks for the tip!

More on that:
Need an exposure crutch?

More on that in Post #47

Welcome to POTN! What do you like to shoot?

Very interesting/useful. I so often take a landscape to find I either have an interesing sky but dark scene, or blown out sky and correctly exposed scene - I then always have to put it right in PP. So should I just be metering off my hand, then recompose and snap.?

Minty wrote in post #7875621
Very interesting/useful. I so often take a landscape to find I either have an interesing sky but dark scene, or blown out sky and correctly exposed scene - I then always have to put it right in PP. So should I just be metering off my hand, then recompose and snap.?

The hand technique works well if the light source is somewhere behind you, or if you have a backlit subject and care more about the exposure for the subject than what happens to the background (will probably get blown).

However, if the sun is vaguely in front of you or beside you then your hand will be in its own shade if you're not careful. You would need to hold your palm flat/horizontal and take a reading from it by pointing the camera down at your palm. That should get you pretty close. Using manual exposure will then allow you the freedom to adjust your composition as you like with no further worries about the exposure getting thrown off. You could use autoexposure and AE lock, but that's only good for a few seconds and for one shot or a quick burst at a time (I think). Manual exposure keeps things simpler because it stays put.

Assuming you go for manual exposure and spot metering, you could also meter off grass and set an exposure from that to between -1 and 0 on the meter, depending exactly on how bright/light the grass is (deep rich green grass is at about -1) and depending on what sort of highlight content your scene has. If there isn't anything in the way of important highlight detail then you could probably meter off the grass at 0 quite comfortably and thus gain a little more shadow detail. However, if you have important highlights in your scene it's best to keep rich green grass back at -1.

Another option, if you have a sunlit scene, is simply to set a manual exposure based on the Sunny 16 Rule. The rule is that in bright (overheadish) sunshine, if you set an aperture of f/16 your shutter speed will be the reciprocal of your ISO. e.g. you can use 1/100 at 100 ISO or 1/200 at 200 ISO and so on. Of course, if you open up the aperture then your other values will need to alter in order to maintain a correct exposure. On a 1.6X crop body you might chose f/8, 100 ISO, 1/400 for a landsacpe, or maybe f/11, 100 ISO, 1/200 at a pinch.

The sunny 16 rule (guideline) can be modified to suit conditions other than brilliant sunshine. See here - http://medfmt.8k.com/m​f/sunny.html.

Whatever method you use, chimp your histogram just to double check you got it right. If not then manual exposure lets you fine tune things easily without faffing about changing your EC, re-metering and re-locking your exposure.

EDIT : p.s. of course, for the palm trick to work you do need to have your palm in the same light as the subject/scene you are shooting. If you're sheltered within the shade of a tree you will not get very good results from a sunlit scene

Many thanks, some new things to try out

Yes a thanks from me as well. This is some really good information and greatly appriciate it being shared.

For people with their faces in the shade, you want your hand in the shade, too.

Adjust the meter according to your hand exposure. Then meter the grass & see where the needle falls.

Using my hand method, skip this step. You've already compensated UNLESS you're using the "Expose to the Right" tut, which is a whole 'nother thing.
It's all in the link I gave you.

A simplified 'meter the hand' calibration, which is less labor intensive than Frank's exposure crutch to get started...

The palm seldom tans, it is rather consistent in brightness regardless of racial group...it is about +1EV brighter than an 18% gray card. So even without following Frank's calibration technique, you can rely upon the simplistic "Read the palm, add +1EV" whether you are a Swede or Finn in the north visitng Laplanders at the end of winter or an African close to the equator in the dead of summer.

I like this discussion. I learned a lot regarding setting for correct exposure. I will try to apply this especially the palm method.