Exposure compensation question

I was just trying to form a thought and, as usual, I came dangerously close to cerebral melt down! Anyway, this is a 2 part question. 1st, if you use exposure compensation to the brightest setting, will it cause more noise to the image? and 2nd, as far as I know I can't use EC when in manual. And if I use it in Av, it will adjust the shutter speed accordingly, which is a wash. But, I can trick the camera by locking the exposure to a higher shutter speed by pointing to a lighter source, with EC all the way up. Would this be worth doing, in trying to keep the noise level down?

As for part one, I'd say no. EC shouldn't affect noise as long as you aren't changing ISO. (My Canon never adjusts ISO as part of EC. I'm not sure about other brands.)

For the second part, I'm not sure what you mean by EC changing the shutter speed being "a wash". Changing the shutter speed is what I would expect EC to do when in Av mode. Remember that EC is a way to compensate for your meter giving you the "wrong" readings due to the scene being brighter or darker than an 18% gray card.

Welcome to my melt down, Matt! Perhaps I left out that I would be trying to keep the shutter speed as high as possible. If, let's say, I was shooting a moving subject in low light and I didn't want to increase my ISO all the to 6400 (from 3200), so to minimize noise, and assuming I'm in Av, the meter tells my camera that at f4, I need to be at 30th of a second. My thinking is that I could lock my shutter speed at a 60th, and crank the EC a full stop to make up for the loss of exposure time. Does that sound right?

Do you have reason to think your meter is wrong? If not, EC isn't really what you want. If the correct exposure is 1/30, f/4, iso1600, changing the EC won't change that. If you need 1/60 or faster and f/4 is as wide as your lens opens, then your choices are upping the iso or underexposing your images. You are better off with higher iso, in my opinion.

Or maybe you could put the camera on a tripod with a pan head? Or maybe flash? If either is feasible, that may help.

Gotchya... I was thinking that, by doing this, it would essentially add another stop "of light" to my image in a light challenged environment.
Thanks, Matt!

Hmmmmm...unless I am missing something, the only two ways to 'lock' in your shutter speed is by using manual, or switching to Tv. If your switch to shutter priority, and your lens only opens to f-4, EC will be moot...you will be underexposed. You might try slow sync ( or another setting ) flash?

More fun related to exposure compensation -

www.photographytalk.com/photography-arti...basics-of-exposure-4

shutterfinger.typepad.com/shutterfinger/...ion-of-exposure.html

laurencekim.com/2009/12/20/your-camera-lies/

neilvn.com/tangents/exposure-metering/exposure-compensation/

Kelly Cook

The fact that I'm losing everyone with this tells me I'm the one that's lost!!!

So here's what I picture in my head. I'm at a concert, the lighting is dim, and I'm using Av mode with no flash. My shutter has to stay at 60, for the sake of argument. But when I point my camera at my subject it says 30. So I adjust my EC to one full stop of over-exposure. I point my camera at something brighter to make it think it needs to be a 60th of a second. Then, I lock that exposure in and take the shot. As my ambient exposure is now 1 stop low, wouldn't the EC being 1 stop up compensate for that? Is that techincally right?
I've got to be missing something obvious... as usual.

Thanks for the links, Kelly. I'll have a look at those.

So I just gave this a try on my 50D. And yes, -1 stop EV compensation in Av mode did move the shutter speed from 1/30 sec to 1/60 sec. This was with a fixed ISO. But my technique would have been to have the camera in Tv mode at 1/60 sec and ISO on AutoISO. Then EV compensation should not be needed (unless the subject rips his shirt off).

Kelly

John37 wrote: The fact that I'm losing everyone with this tells me I'm the one that's lost!!!

So here's what I picture in my head. I'm at a concert, the lighting is dim, and I'm using Av mode with no flash. My shutter has to stay at 60, for the sake of argument. But when I point my camera at my subject it says 30. So I adjust my EC to one full stop of over-exposure. I point my camera at something brighter to make it think it needs to be a 60th of a second. Then, I lock that exposure in and take the shot. As my ambient exposure is now 1 stop low, wouldn't the EC being 1 stop up compensate for that? Is that techincally right?
I've got to be missing something obvious... as usual.

Thanks for the links, Kelly. I'll have a look at those.

If you did as you described you would be underexposing your picture by one stop.

John37 wrote: The fact that I'm losing everyone with this tells me I'm the one that's lost!!!

So here's what I picture in my head. I'm at a concert, the lighting is dim, and I'm using Av mode with no flash. My shutter has to stay at 60, for the sake of argument. But when I point my camera at my subject it says 30. So I adjust my EC to one full stop of over-exposure. I point my camera at something brighter to make it think it needs to be a 60th of a second. Then, I lock that exposure in and take the shot. As my ambient exposure is now 1 stop low, wouldn't the EC being 1 stop up compensate for that? Is that techincally right?
I've got to be missing something obvious... as usual.

Thanks for the links, Kelly. I'll have a look at those.

I've read this 10 times...closed my eyes, and tried to place myself at the concert. I wish I was more experienced, and certain of myself...I can see why you are boggled about it! However... No matter how I calculate, the answer is no...you will still have your subject underexposed.

If I am wrong, I appologize ahead of time!

John37 wrote: 1st, if you use exposure compensation to the brightest setting, will it cause more noise to the image?

EC adjusts what tone the meter is going for. It should tend to over expose, but it depends entirely on what you are metering. If EC is set to +3, and you meter middle gray, it's going to give you the settings to make middle gray 3 stops brighter. If EC is set to +3, and you meter something 3 stops brighter than middle gray it's going to give you the settings to make middle gray middle gray. If you meter something 1 stop brighter than middle gray it will make middle gray 2 stops brighter. If you meter something 1 stop darker than middle gray it will make middle gray 4 stops brighter.

John37 wrote: But, I can trick the camera by locking the exposure to a higher shutter speed by pointing to a lighter source, with EC all the way up. Would this be worth doing, in trying to keep the noise level down?

Noise is going to have to be assessed individually. At what point noise caused by under exposure becomes an issue is part opinion, but also will vary depending on the camera and processing.

Meter lock allows you to meter an area and then recompose without the meter re-adjusting. It's handy when the tone you'd like to make middle gray (or whatever the meter is going for via exposure comp) isn't in the center of your viewfinder.

You are succumbing to the idea that gizmos will make your job easier, but as your meltdown demonstrates they often make things more difficult. Here's how I would go about shooting the concert situation described above. Leave EC to zero. Take a test shot. I'd probably pick an exposure based on experience, but I could just zero the meter or put the camera on an auto mode such as Av. Check the histogram to assess the exposure. Adjust from there. Unless the lighting varies or is uneven across the stage I can just shoot away. If the lighting does change then I might take several test shots, and figure out the settings for those conditions. For instance maybe the edges of the stage are 1.3 stops dimmer than the center, and reduce exposure by 2 stops when the main spotlight is on, etc.... Or I could set the meter mode to spot, and adjust exposure so that the performers faces meter at +1 stop for light skin and middle gray for dark skin. Unless the scene is very even tonally operating in manual exposure is probably going to require less effort and concentration than babysitting the meter. With a little practice you will become very fast at adjusting settings manually.

John37 wrote: As my ambient exposure is now 1 stop low, wouldn't the EC being 1 stop up compensate for that?

Exposure compensation adjusts what tone the meter goes for in any auto exposure mode.

When you say "ambient exposure is now 1 stop low" do you mean 1 stop less than middle gray? Or 1 stop less than middle gray +1?

Is the ambient light background middle gray? If it is dim it should meter less than middle gray.

Proper exposure is an opinion. The meter helps you determine how much light you have to work with, but what exposure and processing results in the "right" tones is up to you.

Thank you all for the input. To clarify, I'm only trying wrap my brain around the concept. I know that, in the event it actally worked, the practicality would be limited, specific and minimal in terms of positive results. I think what got my meltdown started was trying to shoot with my F4 at an indoor basketball game. At f4 I couldn't get any decent shutter speeds and my ISO had to be tapped hard. So I started wondering about the EC feature and if there was any possible way of exploiting it and using it for something other than what it was designed for. It's been cleared up thanks to you all!!

ISO had to be tapped hard

A common occurrence indoors. Instead of sweating buckets of blood trying to keep the ISO down, I focus on NR techniques in post. Of course in the perfect world I would just run out and buy the latest, greatest body.

Kelly