The Fox wrote in post #5248674
I have been looking for a while and have a few questions about proper exposure on my 20d.
1. How can I get better not so blown highlights and not so black shadows in bright sun light? (a.k.a. proper exposure)
2. What is the best way to use my 430ex as fill flash in daylight on people?
3. How can I get the exposure right on indoors?
4. How do you properly read a histogram?
Thanks for answering any of the above questions.
Here it is in a nutshell:
Before answering the questions let's define a few things
1) a "stop" = 1 unit of exposure
2) From one stop to the next, you are doubling or halving the amount of light.
3) 3 things that controls stops are aperture, shutter speed and ISO.
4) Properly exposed white will be white WITH DETAIL (very important)
5) Properly exposed black will be black with detail
6) White with detail underexposed by 2 stops gives you 18% gray (this is what your camera tries to expose to)
7) 3 stops underexposed 18% gray is black (so 5 stops underexposed white with detail is black.
8) Lighting ratio is the difference in exposure from highlights (white with detail) to shadows (black with detail)
So the game is to shoot a scene where the highlights to the shadows are within 4 stops
to retain detail in highlight and shadow
Bright sun at noon produces high contrast or high ratio light. A properly exposed white brides dress will cause lost detail in the shade of a tree. Some of the things you can do about this is shoot your subject in the shade or use a reflector or flash to fill in the shadows. Or just wait for the Golden Hour.
Using the flash to fill in the shadows will bring the lighting ration down a bit. You don't want to let the flash eliminate the shadows but to just give some detail in the shadows.
Let's say your subject is waring a baseball cap and half of his face is in the shadow of the brim. The difference in exposure from the lit side of his face to the shadow is 4 stops difference. The photo would not look good because half his face would be missing.
Use your flash and set it for -1 stop exposure compensation. This would tell the flash at the proper exposure to back off the light by 1 stop (half the light it would normally need)
Now there is detail in the highlights and shadows of the face and it looks natural because you would expect a shadow from the baseball cap to be where it is.
Another technique you might want to read up on is "Dragging the shutter"
Do a search on the forum for it.
Camera meters are pretty sophisticated these days. The average metering setting does a good job at figuring out what is needed.
But if you want more control, you can use a gray card. A gray card is something you can buy at a camera store and it's gray.(duh.) If you let your camera meter take a photo and you average out all the pixels, 18% gray is what you will get. Which is the gray card.
Also you can meter off the palm of your hand. It's about 18% gray.
A histogram is a brutally honest representation of the tonal values of you picture.
The left side of the histogram represents black (a digital value of 0) and the right side represents white (a digital value of 255). The vertical component of the histogram represents how many pixels of each value from 0 to 255. So a very white scene like snow will have a big spike on the right of the histogram and a night scene will have a bit spike on the left of the histogram.
The histogram represents about 7 stops of dynamic range (but on a monitor you can only see about 4 to 5 stops)
If you see the histogram curve clipped on the left or right, you've lost detail in your photo. It can't be recovered. It's beyond the dynamic range of the camera.
You should always shoot average lit scenes where the bulk of the information is on the right of the histogram without it being clipped. Of course there are always exceptions to the rules. You just need to know how to interpret the information on the histogram. Sensors are optimized for more information on the right. If you try to brighten up a dark exposure in post production, you will create "noise" in the very dark areas of the photo. But it's ok to darken a bright photo (as long as the highlights are not clipped or blown out)
I hope it's not too long winded and the information is right. I'm sure others will be adding their 2 cents.