abcdaniel

Thanks Chris B! We're talking in our course about pros and cons of different software, about perception and the tools we use to look at and create images. This discussion here is live, so it is interesting to put it in the teaching mix!

Hey Chris B, thanks for the reply! I think HSL is a true and tested approach/algorithm to handle color adjustments. The implementation here, that is the bug, is spreading out the RGB values in pale colors when pushing down luminusity; then we get saturation. I believe the classical approach to lowering luminosity or brightness is to either keep the RGB-values at the same relative strength when lowering their values (basically subtracting the same value from each of the RGB) or compressing them to a new range, which will actually decrease their spread and thus the saturation. In my courses we talk a lot about perception. Do you have a reference or a link to how your approach fits better to human perception? If this bug isn't resolved, it would be a nice thing to bring into the courses.

My user scenario: I teach at a university. We did not get access to Adobe licenses this semester, and Affinity is much more benign, so now we're using Affinity for remote learning. Thanks Affinity! I'm teaching 60 students this semester, half of which have used Adobe before. That's 60 new Affinity users. I've been ok about switching to Affinity, because I use it privately in parallell to Adobe, I am optimistic about Affinity, and I wanted to stress test it. If there are these kinds of bugs, HSL being one of the adjustments we depend on, Affinity is a no go after the pandemic , and we switch back to Adobe. The students already familiar with Adobe will be disappointed and frustrated, and so will I.

This bug was also reproduced on a friends mac running Affinity Photo 1.8.3 and on my iPad, with the latest version of Affinity Photo for iPad.

Lowering luminosity with an HSL adjustment layer on pale colored pixels might saturate the pixels, instead of making them darker. This is true where any of the RGB values is maxed out, ie at 255. I discovered this with a sky that was slightly blown out. The example image shows blown out reflections of spotlights on the ice in a hockey game. A slight adjustment of luminosity makes the border of the blown out area saturate, in RGB/CMYK base colors. This can be reproduced by purposely filling areas of a pixel layer with colors like 255 255 249 and then applying HSL and lower the luminosity. If you push down brightness far in a brightness/contrast adjustment layer, you will get a similar effect. I consider this a seriuos bug. Lots of source photos have blown out details by necessity, like the hockey rink spotlight reflections in the image. Combine it with jpeg blocking and the luminosity slider is unusable.