Affinity Photo 1.8.2 - Procedural Texture, Reduce Colour Contribution?

[Martin Hunt]

Hi,

I'm trying to use a Procedural Texture filter (with a mask) to reduce the colour contribution of the Red channel and can't get the equation to work.

If I set the Red Channel equation to "0.75*R + 0.25*G" then this works as I would expect, creating a destination red channel value based on weighted contributions from the red and green source channels.

However if I set the Red Channel equation simply to "0.75*R" then my destination red channel gets completely zeroed instead of being reduced to 75% of the source red channel value (which is my aim here).

Am I missing something simple here - isn't there a way to get the filter to simply reduce the destination channel value, or is this a known bug?

Thanks,

Martin.

AP 1.8.2 for Mac.

[Ray S.]

Hi Martin,

 

I'm not an expert in math or equations at all, but if you type 0.75 (without *R) it works like you expect.

 

[GarryP]

I think it’s working fine for me on Windows 10 but I’m not a Procedural Textures expert.
See my attached video where I first use 0.25 on the red channel and then 0.25*R (watch the Histogram Panel).
Try what I try, and if you don’t get the same result then there could be a problem.

[Martin Hunt]

Thanks - that was very useful.

I followed your steps and got the same result, which meant it wasn't my approach that was wrong or the mac/pc thing.
Started over from scratch with my file, doing the same steps as before, and this time it worked as it should.
Still not sure why it wasn't working for me the first time around, but moving on...

Martin.