Matt, thanks a lot. I basically understand the general concept of bracketing and you answer helps. But my original concern was flat photos on a very overcast day. Should I get the very best negative as you have described and then, after I have a good exposure, experiment with development times to get more detail in a flat negative? Also, since I am using sheet film (4 X 5), is there a good trick to identify each sheet as to what speed it was shot so I can make an educated determination of which is best? Perhaps a little sign? I will end up with about 5 sheets and no way to know which is which. The more I read, the less I know
Alexis
Numbering your sheet film holders, with different numbers on each side, like 1A and 1B for the other side, 2A and 2B, etc. helps.
Keeping good notes referencing the holder and side number is also good practice.
Figuring out what your film does in normal contrast, high contrast, and low contrast is good to know. You will, with time, understand how you must expose and develop your film to get the most out of it, in each type of lighting.
In flat lighting you have low contrast. You may choose to keep the negative low contrast and just expose as you normally would, and then develop as you normally would too, and you end up with low contrast negatives that make pretty low contrast prints. Or you can develop the negatives longer to increase the contrast by boosting highlight density. Or you can underexpose a little bit to stretch the existing shadows farther down to being darker than they actually are, and then compensate for lost exposure by developing longer. Or you can do both. Then you end up with a negative with contrast similar to what you would see in normal contrast lighting.
Think of the light in the scene and how it is recorded on film, and subsequently developed, as a rubber band that is elastic. Medium normal contrast lighting means you are recording a certain amount of light with a span from darkest shadow to brightest highlight that is, let's say 10. Bear with me.
That normal contrast is recorded with normal exposure, and developed with normal developing time, which translates to contrast in your negative of 10.
But if the light is lower contrast, say 6, then what's recorded on the film is only 6. If you expose and develop as if it was 10, you will only have 6 in your negative. That will be a flat negative that makes flat looking prints. Sometimes that's desired, other times it's not. When it isn't desired, you have to use the elastic properties of your process, and stretch that rubber band from a 6 to a 10. To get the shadows deeper than they are in the scene, you give less exposure. To get highlights brighter than they are in the scene, you have to develop longer, maybe a lot longer since you also underexposed. This way you can stretch that contrast of 6 to a 10.
Does that make sense? I'm just using arbitrary numbers. They don't mean anything other than giving a relative comparison.
Similarly, if you have a really high contrast scene, you
may want to reduce the contrast you record, as it may be 14 or 15. Then you can take the deep deep shadows and give more exposure to the film to lift those shadows up from the abyss, and then you shorten your developing time to bring those overly bright highlights down to printable levels, so that you contract the contrast 14 down to the normal 10.