Another question I get asked a lot these days is “When I took your workshop years ago you said to open up your exposure (over expose) to make white actually look white but now you say that you under expose all your exposures. What gives?”
I love these ‘years ago’ kinds of questions. When I taught a lot with John Shaw people used to come up to him all the time and confront him on why he was doing or using something different than from what he wrote about in his books which had come out years earlier. His stock response was always “and I drive a different car as well.” I still don’t know what that means.
I guess his point was that things change. We adapt to different sets of circumstances. This is how we grow and become better at whatever we do. If you always did something the same way no matter the advances than you would be stuck in the mud of stubbornness. No one likes to be stuck in the mud of stubbornness, unless, of course, you are a member of congress.
When we all shot film, lo those many years ago, we used cameras that were pretty sophisticated but not nearly as sophisticated as the ones we use now. Also, if you can remember back that far, what we did to film is what we got on film. There wasn’t much chance to tweak the exposure or tighten the composition like we now do on our computers.
So with film we needed as much precision as possible. For any tricky exposures we often used the spot meter for precise metering. If we put the spot on something white we had to over expose the picture to make the white appear white on the film.
We can do the exact same thing with digital exposure and get great results but most of us don’t. Instead we use matrix or evaluative metering, reading the entire frame because matrix/evaluative meters are very, very sophisticated now. But we still have to use our brains to get the proper exposure.
By using our brains I mean we have to realize that with digital cameras we still want the whites to be whites but we are also aware that if the whites are too white than we will be in trouble. Blown out whites (whites that are too over exposed) in digital photography are not only detailless (not good) but also dataless (really not good). Without data our computers are helpless to make changes in the image. In other words, computers won’t have any effect on these blown out highlights no matter what we do. These areas will always be blown out, distracting, dreadful whites.
To prevent getting blown out highlights when using matrix/evaluative metering I often fudge on the exposure and slightly underexpose the picture. I do this often when shooting landscapes because there are always hidden areas that I don’t recognize that can easily blow out. I also always do it when shooting in significant sunlight because the increased contrast will usually lead to some very bright whites and some blown out whites.
How much do I underexpose? My default amount is -.7 stops (2/3 of a stop under). I use the exposure compensation setting on my camera to set this amount so every picture I take is slightly underexposed and looks dark on the LCD on the back of my camera.
Even though I do this I still check the histogram after every shot. Sometimes I take all the exposure compensation off if the histogram is too far over to the left (dark) side of the graph. I rarely add more compensation though. If I find I need to shoot at -1 or even -1.3 stops than the light is too contrasty and I know I should stop shooting until the light improves.
So if the light is low contrast it is fine to spot meter something white in your picture and make your meter read a stop or so over exposed just like we used to do with film. If the light is stronger though, my experience tells me that I if I do this I will get blown out highlights in my picture. To avoid this I set the camera to under expose a bit. The resulting picture will be darker than it should be when I first see it on the back of my camera but I know I can fix it later in the computer.
It is important to realize that all of these are just guidelines, nothing is written in stone. There are no hard, fast rules for proper exposure because the light is always changing. By using the guidelines above you will have to do a minimum of fussing to adjust your exposure.