camera question?

Question

What does it take to make correct exposure of a sunlit subject in an interesting area with a successful composition in Aperture Priority?

Answer 1

A thought-out selection of metering mode and/or exposure compensation.

Aperture priority lets you set the aperture (and ISO on a digital camera) constant, and the camera's meter will determine shutter speed.

You can adjust how aperture priority will work by choosing a metering mode to reflect what portion of your frame the camera uses to judge exposure. Spot metering will judge exposure based solely on the basis of the very center of the frame (or if you use an exposure lock, a point of your choosing). At the other extreme, you could average the whole frame to determine exposure. Look at your manual for the different metering modes on your specific camera.

Most cameras also allow you to compensate a couple of stops over or under what the default exposure based on your metering mode is.

Example: I'm shooting a wedding where an African American bride is the subject on a sunny day. If I meter off of the white dress (which will be MUCH brighter than everything else), the camera will try to set a shutter speed so that the dress is 18% gray at a given aperture. This will under-expose the entire image. I can either exposure compensate up +1-2 f/stops and keep metering off the dress, or I can switch modes and spot meter from her face (depending on her skin tone, this may over-expose and I'll need to compensate down to avoid blowing the highlights in the dress). I can average meter off the whole scene, but depending on the brightness of the surroundings also risk blowing the highlights in the dress (overexposing).

Remember that the camera will try to make whatever you meter off of "in the middle" of the camera's dynamic range.

As you can see, under some circumstances using aP is more complicated than just choosing a correct manual exposure.

Answer 2

Well it depends on if your scene is evenly sunlit or if you have areas of light and dark in your scene. If evenly lit just set your f-stop where you like and the camera will set the correct shutter speed. Just be sure its not too low to hand-hold (any shutter speed that is the reciprocal of your lens length is fine. So if you're using a 100mm lens keep your shutter speed at 1/125 or higher.)

Now if your scene has areas in sunlight and in shade things get tricky. If you expose for the highlighted area (the sunlit part) your shadow areas will be very dark with little or no detail. If you expose for the shaded areas then your highlight area will be "washed out" with little or no detail. So what to do, what to do? We'll use the "Averaging" method for computing exposure.

If your camera has a setting for "Spot Metering" now is the time to use it. If not, simply zoom in on the highlight area, take your reading and then zoom in on the shadow area and take your reading. Just remember which is which.

Change to manual mode and meter both areas. NOTE: Set the shutter speed, say to 1/125 and DO NOT CHANGE IT! Suppose the highlighted area needs f8 @ 1/125 and the shadow area needs f2 @ 1/125. Make an exposure at f4 @ 1/125. How did we get f4? Simply by counting up from f2 and down from f8 (f2, f2.8, f4; f8, f5.6, f4).

If you happen to carry a calculator with square root on it you can compute it mathematically. First, multiply 2 by 8 = 16. Now find the square root of 16 = 4. Suppose our values were f4 (shadows) and f16 (highlights) @ 1/125. Again counting up and down from the 2 extremes will land us on f8. Or, if we multiply 4 by 16 = 64; square root of 64 = 8.

This is also a good time to try "bracketing" your exposures. After taking one at f4 @ 1/125 try one at f2.8 @ 1/125 and one at f5.6 @ 1/125. You now have 3 exposures to choose from. The one that looks best is the one to keep. If our averaging called for f8 @ 1/125, take one at f5.6 @ 1/125 and one at f11 @ 1/125.

NOTE: This is somewhat simplified. Its possible to end up with a value like 4.7 (f2.8 multiplied by f8 = 22.4; square root of 22.4 = 4.7) so here you'll just have to set your f-stop between f4 and f5.6, erring on the low side. In all likelihood f4 would be ok.

Answer 3

Experiementation. You don't say if the subject is backlit and that's tricky and would possibly require fill flash. Also, the time of day plays a part, sunlight as the sun is fading, is more yellow and you may have to compensate for that.

Answer 4

Knowledge.