Understanding thick-lens optics
The article with the above title is about using principal planes and pupils in geometrical optics. The example lens has an entrance pupil downstream of the exit focal point. This situation was deliberately chosen because it is not usually considered in optics articles, even though it can occur in macro photography.
There is nothing original in my new article with the above title; it's just a note to remind me how things scale with camera sensor size. If you see a photographer with a large lens on a tripod trying to photograph a bird in a tree, tell him: "Why don't you use a 30 mm lens? You will get more depth of field."
I have added an article about linear camera profiles in Adobe Lightroom. Lightroom applies a hidden tone curve to the raw data in addition to the gamma encoding and any user modifications. Some users, me included, would prefer that no such tone curve be applied. This was supposedly achievable by using the new linear camera profiles. Unfortunately, I found that some nonlinear tone curve is still applied to all photos.
