Interference Pattern on image when using MONO demosaic

Software RawTherapee
1

Using the Mono option to make black and white jpegs from my RAW photos shot with LUMIX gh4. The pictures often get a interference pattern on top of them after processing. Doesn’t happen with the amaze demosaic. The pattern is not visible inside RAWtherapee.

Uploading an example image:

P2850141_1-1
P2850141_1-12515×1887 3.76 MB

And the same image in colour (amaze):

P2850141-1
P2850141-12364×1774 7.65 MB

I know i can use the Black and white filter on a colour image but the mono demosaic proved more handy and i prefer the results. Anyone has an idea how this intersting phenomenon can be avoided?

2

In darktable, similar patterns are sometimes caused by lens correction. Did you enabled it in RT?

1 Like
3

Try to zoom in to 200% or so. To really see what’s going on, turn off lens correction, which is what causes the swirly pattern.

By not disabling the demosaic step, which is what you do with the mono option.

2 Likes
4

It indeed was the lens correction, and only occurs with one of my lenses. So thats why i wasn’t getting it consistently.

Saw the very regular noise pattern in the MONO images, has a style to it. Learned something today. Thank you people!