help with exposure indicator

[cool_al3e]

hi guys i m new to this forum and also to photography.However recently i started using manual photography after understanding bits of all.the problem i face is that the exposure indicator doesnt gives me the proper info.like sometimes in low light conditions i set proper ISO,F and shutter speed according to indicator,so it comes at 0 which means optimal exposure,however when i release the shutter the picture is either under exposed or over exposed.even when the indicator says 0 plz help me with this...i am using d5100 with 18-55mm lens

[autofocus]

It's probably a factor of your subject matter, and how your camera is metering the frame. An example might be 2 or 3 chaps in black tuxedos standing in front of a black limo. The camera's meter sees all that black/dark tones and tries to indicate what the exposure should be based on all that black. You will probably wind up with the black part of the image being properly exposed at the expense of blown out faces. The trick is to learn how to read situations like that and outsmart the meter by underexposing that shot just to be sure you will get the faces properly exposed..obviously, the exposure on the faces is what's most important. Bottom line, the meter is only just so smart in trying to average out all the light, and these are the times you have to outsmart the meter. That is the reason why you see photographers with meters take incident readings right up to the subjects face

[cool_al3e]

so i think i got it...lets get back to the example for that i will have to select spot metering and spot the faces of either and lock the exposure and than focus and release the shutter right?

[AHutch]

Originally Posted by cool_al3e

hi guys i m new to this forum and also to photography.However recently i started using manual photography after understanding bits of all.the problem i face is that the exposure indicator doesnt gives me the proper info.like sometimes in low light conditions i set proper ISO,F and shutter speed according to indicator,so it comes at 0 which means optimal exposure,however when i release the shutter the picture is either under exposed or over exposed.even when the indicator says 0 plz help me with this...i am using d5100 with 18-55mm lens

What metering mode are you using? Multi-Matrix, Spot?? Can you post an example of one of your under/overexposed photos?

[autofocus]

Originally Posted by cool_al3e

so i think i got it...lets get back to the example for that i will have to select spot metering and spot the faces of either and lock the exposure and than focus and release the shutter right?

Spot metering is just one of your tools, and will vary as to when it's needed. In mixed lighting situations, as in your typical room shots, matrix metering or averaged metering is still probably your best setting. Just remember, if you are shooting into an area with a bright ambient lit window, once again, the meter will reflect that, and you will need to compensate for it when you manually set your exposure. Also, when your subject is backlit your camera's meter will see all that light, and if you zero your meter you will most often end up with a dark, underexposed subject. Spot metering and/or overexposing that shot will yield in a better exposed subject, but at the expense of blowing out the details in the background...but, it's always the subject in the shot that you want exposed correctly, and not necessarily the background. Your best meter will always be your eyes and your brain...evaluate the lighting conditions, and learn to adjust your settings accordingly.

[inkista]

You are smarter than the camera.

The camera doesn't know what you're taking a picture of. It's relying on the image data and the metering system to crunch through the image data to come up with an exposure setting. But because the AE (autoexposure) system is mechanical and treats all scenes the same, it's bound to be wrong, sometimes.

Which metering mode you use can alter the outcome of how the AE system works, but no mode is ever going to be 100% accurate all the time. You have to understand how this system works.

In a very simplified scenario, the AE system is basically just taking all the values across the sensor, assigning a value that corresponds to how light/dark each pixel is, and then averages all those values. The assumption the AE system typically makes is that that average is going to be in the middle of the exposure range. So, the exposure settings are adjust to place it in the middle of the exposure range ("middle gray".)

This works great if your scene has as much light in it as dark. But it doesn't work so great if your scene is biased towards one end of the spectrum or the other.

If you're, say, shooting a night scene, with a lot of black in it, then your average value is actually going to be closer to black than to middle gray. And the AE system will overexpose (you typically get brown skies with night shooting this way). And you need to bias the exposure towards underexposure.

If you're, say, shooting a snow scene, with a lot of white in it, then your average value is going to be closer to white than to middle gray. And the AE system will underexpose. And you'll need to bias the exposure towards "overexposure". Ditto a beach scene with a ton of additional reflected light.

This is why we like having full Manual mode and exposure compensation. "0" doesn't mean "correct exposure". It means "what the camera thinks is correct exposure."

Average/Matrix, Center-Weighted, Spot, etc. changes which data is looked at and how the "average" value is determined, but overall, it all works pretty much the same. It's up to you to figure out what you want to expose for in a scene. What's more important to you in each case: highlights? shadows? midtones? What do you want to emphasize? What's the focus of the image? No metering system in the world can figure that out. It's up to you.

Learn to use your meter before you take the shot, and your histogram after.

[AHutch]

Cool_al3e, let me attempt to bring it back to your problem at hand. You say that in "low light" situations, you are experiencing either under or over exposure. One of the other questions I would ask other than the ones I posed above is, how "low" is the light? Is it indoors with no natural window light? Flash or no flash?

Given all the talk about how cameras have a hard time getting the metering right, I would beg to differ. Today's DSLRs have metering systems that are extremely sophisticated. Even with my "old" Canon 40D, it will get the exposure to within +/-1/2 stop, 95% of the time when set to Evaluative (Matrix) metering mode.

Having said that there could be a number of answers to your problem. It could be that you are using spot metering where matrix metering would give you a better result. It could be that the lighting is very low and you may need to adjust the ISO to give the camera a better opportunity to read the scene. Having said this, I'm very puzzled that you say these low light scenes come out either under OR over exposed! Although that would lead me to beleive that you are using spot metering whereby you are just taking a reading from the wrong spot.

If you could post an example it would go a long way to helping us diagnose the problem. otherwise if you could give us more details as to the metering mode you are using, whether it happens in ALL low light situations, what kind of low light you are referring too, what do you set the ISO at in these situations, etc. The more detail you can provide, the better.

[autofocus]

Given all the talk about how cameras have a hard time getting the metering right, I would beg to differ. Today's DSLRs have metering systems that are extremely sophisticated. Even with my "old" Canon 40D, it will get the exposure to within +/-1/2 stop, 95% of the time when set to Evaluative (Matrix) metering mode.

Sorry AHutch, but I have to beg to differ with your beg to differ. Regardless how sophisticated the metering system is there will be plenty of times that you have to out guess it. Just like inkista mentioned above shooting in very bright or very dark ambient, or backlit situations will always throw off the meter. I see from your website that much of your work is car and nature photography, and most of the time matrix metering may be fine for that. But a person shot against a very bright backlit scenario, or a snow or beach scene will almost always underexpose the subject. That is why we rely on a hand held incident light meter when we shoot people..especially when faced with tricky lighting situations.

[AHutch]

Originally Posted by autofocus

Sorry AHutch, but I have to beg to differ with your beg to differ. ....

I never heard that one before!

You are very correct. There are definitely times, like those situations that have been mentioned, when you cannot rely on the camera's meter to get the exposure "correct" and it is something I talk about on my website. But to try and clarify my point, I often hear some form of statement that implies that a digital camera's meter leaves a lot to be desired. What I am getting at (particularly as it applies to the problem presented that states under/overexposure in "low light" situations as opposed to "high dynamic range" situations) is that in "typical" situations your meter will get it "correct" 95% of the time. But this begs the question, how often does one shoot a "typical" scene!? In those non-typical scenes (e.g. high dynamic range), absolutely, you have to get creative with exposure and not rely on the camera's meter.

This leads into why I'm puzzled by Cool_al3e's problem, because it seems to imply that it is a constant problem in low light situations (typical) as opposed to being a problem in "high dynamic range" situations (non-typical), or maybe I am just reading his problem wrong. In fact, I suspect, as you have mentioned in your responses, that the problem occurs during those difficult metering situations (high dynamic range) rather than "low light" given the likelihood that the low light is causing a large difference between the "dark" areas and the "bright" areas of the scene. Further, the problem may be being exaggerated by the use of spot metering on the wrong areas of the scene.

Hoping all this makes sense to Cool_al3e, certainly don't want to confuse the issue!