Ignoring the brightness falloff towards the corners, which is easy to deal with in image editing and may prove to be esthetically appealing, the most important measure of the purple-corner effect is the change in chrominance (that portion of color that is unrelated to luminance). CIELab provides a formula for calculating chrominance: (a^2 + b^2)^.5…. [Read More]
Archives for January 5, 2012
NEX-7 — Lens testing for purple corners
I’ve now completed making the test images for the following lenses, using the methodology of the previous post: Sony 16mm f/2.8 E mount Leica Tri-Elmar 16/18/21mm f/4 Leica Super-Elmar 18mm f/3.8 ASPH Leica Elmar 24mm f/3.8 ASPH Leica Elmarit 24mm f/2.8 ASPH Zeiss Biogon 35mm f/2 Leica Summilux ASPH 50mm f/1.4 In this post, I’ll report the… [Read More]