Say you are taking a picture of your child skiing down a slope. A student asked me this the other day.
So I produced a kid on a hill and shot that:
OK, it was a white piece of paper with a scribble looking not very much like a skier. But still. The camera thinks my white sheet is gray (that’s the assumption built into reflective light meters) and produces a gray picture. The histogram will be “in the middle”.
If you now use “exposure compensation” (the +/- button) and turn it up to +2, you get something that looks much more like it:
And if the bump in the histogram is not yet close to the right edge, you can go even higher.. like +2 3/4:
And more and we bump against the right edge and lose detail, so we stop there.
Next time you shoot your kid skiing down a hill, and it’s all white, remember that. “Your picture looks grey unless you tell the camera otherwise”.