What’s the difference between a camera and a human eye?
Haje Jan Kamps

Classically trained artists will tell you that ideally, it is always best to work from direct observation rather than reference photographs. This article neatly illustrates why: the human eye can discern more subtleties of color, and a broader range of light and shade, than a camera. For this reason, pictures painted from reference photos often end up looking a bit “flat” compared to ones painted from direct observation.

On this photo, for example (admittedly taken with a cheap point-and-shoot), I remember that there were all manner of things in the barn (including a cow or two) that I could clearly see when I took the photo, but that are not visible on the photo, which shows the inside of the barn as almost pitch black: