And "Difference" looks perfect too. And I erred earlier in suggesting that Subtract and Difference are the same thing and obviously they are not. My Bad.

On Sat, Oct 1, 2022 at 6:36 PM Phyllis Smith <phylsmith2017@gmail.com> wrote:

BUT Subtract mode when using the Red/Green png's does not appear to be correct. I will keep analyzing.

I think difference might be due to alpha channel in pngs ...?
Maybe, but in doing more tests I see that Addition looks 100% correct. I just started using capture of their files. See Addition attached with URL's on the left and CinGG on the right.