08Jan
Exposure Compensation made simplecategories: photography, technical
I went out to shoot a little demo of how a light meter works this morning.
I shot a very white scene; a stick on some snow—and a very dark scene; a very wet, dark manhole cover (it was almost black). The top two pictures are how the two subjects looked to me in reality. (I had to use an exposure compensation setting of PLUS one and two-thirds for the snow and MINUS one and two-thirds for the dark manhole cover.)
The bottom two are how the light meter saw them with an exposure compensation setting of ZERO—normal exposure.
The important thing to notice here is how the meter tries to make everything gray—the bottom two pictures.
Here's a little essay I wrote a while back on this subject.
Here’s a fact. If you took a picture at the north pole on a sunny day—that’s in blinding snow—your camera would make an exposure error. It’s not smart enough not to. So here’s the question: Would it make a picture that was too light; overexposed—or too dark; underexposed.
Wrong! (I know that was presumptuous of me, but please play along.)
If you fill the frame with bright snow the camera is going to underexpose it. The picture will be too dark. Light meters have been built to make everything a middle tone—not too bright and not too dark. It’s a safe place to be. So when your meter sees bright white snow it wants to make it gray—yes, gray snow!. (If it sees black dirt it will make that gray, too—it does not discriminate. It wants to put everything in the middle. The middle ground is safe when you’re exposing photographs.)
A picture of snow that’s too dark?—somehow that’s just wrong. And though you feel unqualified, you are the only thing between your camera and certain types of exposure errors. The problem is knowing which ones, isn’t it?
Well, the digital camera let’s you off the hook a bit. You can see your photos as you shoot them. And then, you can compensate for whatever meter errors are happening. You will use the exposure compensation button. It's that button on your camera someplace that has a little plus and a little minus sign on it. Plus means brighter. Minus means darker.
The important thing to notice here is how the meter tries to make everything gray—the bottom two pictures.
Wrong! (I know that was presumptuous of me, but please play along.)
If you fill the frame with bright snow the camera is going to underexpose it. The picture will be too dark. Light meters have been built to make everything a middle tone—not too bright and not too dark. It’s a safe place to be. So when your meter sees bright white snow it wants to make it gray—yes, gray snow!. (If it sees black dirt it will make that gray, too—it does not discriminate. It wants to put everything in the middle. The middle ground is safe when you’re exposing photographs.)
A picture of snow that’s too dark?—somehow that’s just wrong. And though you feel unqualified, you are the only thing between your camera and certain types of exposure errors. The problem is knowing which ones, isn’t it?
Well, the digital camera let’s you off the hook a bit. You can see your photos as you shoot them. And then, you can compensate for whatever meter errors are happening. You will use the exposure compensation button. It's that button on your camera someplace that has a little plus and a little minus sign on it. Plus means brighter. Minus means darker.
05Jan
What IS that stuff?categories: photography, technical
Part one:
Here's a "photograph" that Victoria posted this morning of a solid blue sky.
I have lightened it and increased the contrast just to make Victoria feel worse than she already does about her dirty CCD sensor.
All that stuff you see there is normal build up of dust and dirt. (There a big chunk in the top right corner.) If you want to feel lousy about YOUR camera take a picture of a white wall at the smallest f-stop you have.
Your CCD chip probably looks like Victoria's. If you use a large f-stop it will look perfectly clean. (The smaller the opening of light the sharper the shadows of the dirt, right?) So to make Victoria feel better I photographed a white wall at f22 with my camera. That's my next post.
Part two:
So here's my picture of a white wall. Ironically, this is the cleanest I think my CCD has ever been.
Yes, there is a big piece of dirt there but that's just par for the course. (Mine usually looks just like Victoria's. I can't explain why mine looks so good today. I must be doing something wrong.) Seriously, this is the cleanest CCD chip I have ever seen. Not kidding.
Anyway, there are a bunch of ways to clean it.
1.Some cameras have an auto clean function that works pretty well.
2.You can send it to the manufacturer and have them do it. If you ever do that, run the white wall test when it comes back and you will see what you're up against. They can't get rid of all the dust, either.
2A. You can buy the cleaning kit of swaps and special solutions that the manufacturer will use to clean it. They're pricey and will drive you a bit crazy, too.
3. You can do what I do which is blow it with a can of high grade air (just for this purpose) BUT YOU HAVE TO BE VERY CAREFUL! THAT CANNED AIR CAN SHOOT SOME LIQUID THAT CAN DO PERMANENT DAMAGE TO YOUR CAMERA. DON'T SHAKE THE CAN! HOLD THE CAN LEVEL! DO TEST SPRAYS BEFORE YOU SHOOT! SHOOT LIGHTLY! THIS IS NOT RECOMMENDED BY THE MANUFACTURER!
4. You can do nothing. It's what I do most of the time. If dust shows up someplace in a picture you can usually fix it in editing.
5. Know that the dust is really going to show up when you shoot something like a plain wall or sky at a very small aperture. That's when it's most noticeable.
6. To avoid dust, turn your camera off when you change lenses. The electric charge can attract dust. Don't leave you camera open without a lens or lens cap for very long.
7. DO NOT GO CRAZY ABOUT THIS.
8. Most importantly, understand that CCD cleaning is not for anyone with any kind of compulsive disorder.
2A. You can buy the cleaning kit of swaps and special solutions that the manufacturer will use to clean it. They're pricey and will drive you a bit crazy, too.
