Yesterday I posted this piece on testing for lens decentering using manual focusing. Today I’ll explore an autofocus variant that might be useful when there’s not enough depth of field for the first technique to work well. I mounted a Sony 90mm f/2.8 macro lens on an a7RII and set it up about 20 feet… [Read More]
Serial monogamy in camera ownership
You see it all the time. “I’m bailing on Canons, and switching to Sonys.” “So long. Nikon; hello Fuji.” I have never understood how some people approach buying cameras like getting married. Cameras are tools. They exist to make photographs. There are many kinds of photographs. Some cameras are suited to making a certain class… [Read More]
Testing for decentering by the numbers
Yesterday I posted the results of a fairly simple decentering test that requires only an ISO 12233 target, some lighting, a tripod, and a few minutes. Today I’ll show you what happens when you use a slanted edge sharpness analyzer — in this case, Imatest — on the images you saw yesterday. Here’s a crop… [Read More]
Testing for decentering by eye
[Edit. Although I’m leaving this post up because several people have linked to it, I now recommend a different method as quicker, easier, and less prone to false positives: Simple decentering test And now back to the original post:] You hear complaints all the time about the quality control of various lens manufacturers, and horror… [Read More]
A photon transfer capture protocol
Warning: this is a technical post that assumes a fair amount of knowledge on the part of the reader. Jack Hogan and I have been working on photon transfer analysis of sensors for some time. He and I wrote some Matlab code to analyze pixel response non-uniformity (PRNU), to plot complete photon response curves, and… [Read More]
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