Yesterday, I presented material on how people’s ability to perceive small – and not so small – luminance changes varies with spatial frequency. Today, I’ll talk about how our ability to perceive changes in chromaticity (color without luminance) varies as spatial frequencies are manipulated. Yesterday, I started with the graphs and followed up with the… [Read More]

We’ve seen that the sensitivity to luminance variation falls off as the luminance spatial frequency increases. If turns out that it also falls off as spatial frequency decreases, giving a band-pass filter effect, which sharpens edges, and gives rise to the Mach Banding that we’ve been looking at in the preceding posts. There are many… [Read More]

I reworked the luminance step wedge of yesterday’ post so that it consists of 10 Delta-E steps from zero to 80 along the gray (a* = 0, b* = 0) axis: The Mach Bands are evident. Then I created a similar image, with L* = 50, b* = 0, and a* starting at -40 and… [Read More]

Inspired by the last three posts, I’m starting a series of posts on spatial considerations in color vision, which an emphasis on what’s important to photographers. We’ll get started today with an illustration: Take good look at this image from a normal viewing distance: The bars are even steps along the grey axis in a… [Read More]

I ran the FFT analysis of yesterday’s post on a couple of more images. First, this old chestnut (thank you, Fuji):   Here’s what I got: For the last three octaves of spatial frequency, the two chromaticity components are about the same distance below the luminance component. Then there’s this image (thank you again, Fuji): Here’s… [Read More]