 Shawn Wilson |
Digital Rebel - exposure issues In an effort to learn more about what settings have what effect, I took a picture in Program mode and then in Manual mode with the same settings. The pictures came out virtually the same. I noticed that P mode used evaluative exposure control and M mode used spot, but I know what that's about. The problem is that in the viewfinder the exposure meter is dead on in P mode, but the same settings in M mode show a severe underexposure. To make the M mode show a dead on exposure, I have to slow the shutter down and the resulting picture is way overexposed to my eye. What would be making the exposure meter be off so far? Is it the metering mode maybe? In the pictures below, the top one is P mode where the exposure meter says it's perfect, and the bottom one is M mode showing a severe underexposure. Any help is appreciated! Thanks!
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Jon Close |
P. 84 of the user manaul. P mode is Evaluative, M mode is Centerweighted, both use Partial ("large spot") if you press the * (AE-L) button. Evaluative and Centerweighted can give different exposure values because they measure and weight the scene differently. When using Partial, and to some extent Centerweighted, you have to pay more attention to the "tones" being metered and apply exposure compensation if your metered subject varies from 18% gray. The Evaluative algorithms attempt that kind of correction automatically.
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
If the spot when in spot metering is on a dark spot, it'll say under exp if what you had as a shutter/apeture combo didn't sound right to the camera. evaluative read off a larger area. little bit of white wall, little bit of whatever the other stuff is. made the meter think everything evens out. You'd see a flip flop if you used spot meter on something lit with a spot light, and evaluative tried reading the spot lit area with the dark stage area and the unlit curtain in the background.
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Shawn Wilson |
If I was going to do a group photo, then what would be better you think? Would it be better to use an evaluative or spot mode if the background is fairly far away, light in color, and on the dark side.
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Jon Close |
http://photonotes.org/articles/beginner-faq/cameras.html#metering is a short description of each of the metering modes. P.S. Your sample photo had high contrast - large areas of white (walls) and black (computer screen, tray, coat, hat) and very little of any tones inbetween. Evaluative gave a good exposure value, as Gregory stated Centerweighted read too much of the central black areas as 18% gray. Re your group photo - Evaluative is probably the best choice for someone not experienced in applying exposure compensation based on judging the tonal values of a scene.
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Shawn Wilson |
I've also noticed that in auto modes, my camera often uses ISO 400. I've taken some test shots and I plan to take more, but do you know where noise starts to become an issue as far as this sensor and ISO speed goes? I plan on making 8x10 prints out of these particular pictures if that makes a difference.
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Jon Close |
Re - noise v. ISO, http://www.dpreview.com/reviews/canoneos300d/, especially, http://www.dpreview.com/reviews/canoneos300d/page13.php. If you decide ISO 400 is too noisy for you, then don't shoot in the Basic exposure modes (green box and icon modes). Shoot instead in P (similar to green box) or Av, Tv, M. In these modes you can set ISO to 100. These Creative modes are preferred to teh Basic modes because you can also set a specific white balance, you can select a specific focus sensor, you can apply your own processing Parameters instead of the Parameter Set 1 default, you can save files as RAW+JPG instead of JPG only, etc.
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