Help with CA correction with RT

Software RawTherapee
1

Hi there! I’m a new member here, and I’m trying to learn how to use RT as an alternative to ACR/LR 5.
I’m already convinced that RT is very powerful alternative, but as many people have found out, it has a learning curve that goes straight up the wall! :slight_smile:

I have a photo taken with an old Sigma 400mm lens which exhibits an ample amount of CA. Here’s what RT sees with the “Default” profile.

Here is what Lightroom can do with “Auto” for exposure, and manual CA tweaking in the “Lens Corrections” > “Color” tab.

I’ve messed with the sliders in RT, but it adds a different color if you move too far in any direction. I can’t make it disappear no matter what I do! Is there something simple that I’m missing?

2

Firstly, any lateral CA should be gone thanks to automatic CA correction which is enabled in the default profiles.

The remainder is longitudinal, and is best removed with the Defringe tool. It desaturates narrow color outliers, and in the default profiles has a curve applied that limits it to the purple fringing that your lens experiences.

3

Just for reference, Defringe is on the Detail tab:

It should fix the leftover longitudinal fringing right up for you. :slight_smile:

4

Aha! There, I knew it probably something simple… I was trying to use this:

749×438 315 KB

Thanks so much for the quick reply! Here’s a before/after of what I’m getting now:

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