Help understanding AEL button to check the exposure of a image on A200

Started Apr 22, 2009 | Discussions thread
tom
tom
Senior MemberPosts: 2,718
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Re: ok, but here's how I do it
In reply to kenju4u, Apr 24, 2009

I don't have this camera, but here's how I use the AE lock & the two pointers on my camera.

I don't use this feature all the time but usually use it when doing landscapes or when setting up for a number of similar shots.

If I'm in P, A, or S modes I will set the composition of the shot the way I want in the View Finder. When I do this , I look around the scene to see if there are any very bright areas or very dark areas.

Then I press and hold AE lock. I re-aim the camera so the center spot circle is over one of the areas I'm concerned with. Then I check the pointers. Since one pointer will be on '0' (with exp comp set to 0), I check the other pointer. Depending on what I am shooting (either print or slide film on my Maxxum 7 or when using one of my DSLRs), I want the exposure in the light or dark part of the scene to be within a certain range of the 0 point.

Some examples:

1. Color print film (not important for your camera but it serves as a contrast to the other cases). Color Print film is very tolerant of of over exposure, but very intolerant of underexposure (negative gets very grainy/'noisy'). So I want the dark areas to be no more than 1.5 stops below the 0 point. If, for example, the shadow area (where I wanted to show some detail) reads -2. ev or lower, I will adjust exp comp in the + direction until the dark area is no more than -1ev below the '0'. This whole operation takes about a second to do. The negative comes out overexposed, but is still very easy to get printed to the correct values.

2. Color slide film or DSLR: Both are very intolerant of overexposure. Slide film has an added complication in that it has limited acceptable exposure range both above and below '0'. DSLR is more forgiving in that it is more tolerant of underexposure. In these cases I'll check the bright areas. If they are more than about +2.5 ev there is danger that the brights will be blown out and unrecoverable. So I will adjust them by setting minus exp comp to bring them back into range. With the DSLR, I'm not too worried about the dark areas, because I can fix in post processing. The only concern would be if the dark area is very large, setting it too low could make those areas noisy when increasing the brightness in post processing, but I haven't found that to be much of an issue.

For any of the cases once I set the exp comp, I release the AE lock and go back to the original composition and let the camera set the exposure normally (but with my exp comp setting). This entire process only adds a couple of seconds to taking the shot, but for things like landscapes that's less of an issue than getting the exposure the way I want.

I usually don't use AE lock for setting the exposure on a different part of the scene and recomposing. Instead of doing that, I'll use "M" mode with spot metering. And then set the exposure based on a specific area -- no AE lock needed. In fact for my cameras, pressing AE lock in M mode switches to 'manual shift' where the ev of the shot is locked, but turning the control dial changes both S and A while keeping the orignial ev. This is good for taking a number of shots that vary the DOF or apparent motion in the shot while not changing the overall exposure.

Tom

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