Harry Nyquist was a Swedish-American engineer and physicist who spent much of his career at Bell Labs. In the 1920s and 30s he worked on telegraphy, feedback stability, and thermal noise, and in the process laid down results that became bedrock for how we think about sampling. His name is attached to a simple rule… [Read More]

Here are the same images as the preceeding post, but presented with Lightrooms profile correction and LaCA correction defeated. In the center:         And in the corner:   The lens corrections are lifting the corners and hiding the vignetting at f/4.     This is a fine lens, considering its design emphasises… [Read More]

In the earliest days of photography, exposure was judged by experience, trial and error, and often by educated guesswork. As materials became more sensitive and photographers sought greater control, metering systems emerged to offer a more systematic approach. One of the first formal systems was extinction metering. The principle was simple: a card or device… [Read More]

Yesterday I posted images of aberrations taken three at a time using a Siemens star as a target. Today I’m posting the same set of aberrations in the same format using a classic image processing test image. You will see that it’s much harder to sort out what the aberrations are doing to the images…. [Read More]