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Author Topic: Correcting *Green* Chromatic Aberration in C1 - what options?  (Read 1103 times)

narikin

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Hi, I know and use the purple fringing slider to remove CA on fine lines, but unlike Lightroom, there is no option for green aberrations.
What are people doing to remove this?

I have a few IQ4 images relying on very fine lines/ hairs, and some are coming out green, wondering how best to fix this.
Masked layer with strong color editor adjustment, painted in where needed?

Thanks all
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Bart_van_der_Wolf

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Re: Correcting *Green* Chromatic Aberration in C1 - what options?
« Reply #1 on: March 11, 2019, 10:03:29 pm »

Hi, I know and use the purple fringing slider to remove CA on fine lines, but unlike Lightroom, there is no option for green aberrations.
What are people doing to remove this?

Doesn't the automatic CA correction (select Analyse, with the active variant) solve this? Have you already applied Diffraction Correction, does the image require any noise reduction?

Quote
I have a few IQ4 images relying on very fine lines/ hairs, and some are coming out green, wondering how best to fix this.
Masked layer with strong color editor adjustment, painted in where needed?

Do you have an example you could share? Is it really CA, or are we may be dealing with colored specular highlights?

There are many possible ways of approach possible, depending on what we're actually dealing with.

Cheers,
Bart
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narikin

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Re: Correcting *Green* Chromatic Aberration in C1 - what options?
« Reply #2 on: March 13, 2019, 12:03:33 pm »

Thanks Bart.

its hard to post a clean TIFF example, as jpegs are not fine enough, but here's something. (200% screen grab)



To my mind its Green Chromatic Aberration, but I may be wrong.
I fixed it with a layer mask and color editor adjustment with big -Sat selected, just painted it out with the mask brush. Luckily I can get away with that here. Much rather there was a 'green fringing' slider in C1 though.

Yes, the specific lens profile correction was selected and used. Didn't fix it though.
Phase One 150mm, f3.2, ES on IQ4-150.
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Bart_van_der_Wolf

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Re: Correcting *Green* Chromatic Aberration in C1 - what options?
« Reply #3 on: March 13, 2019, 01:29:49 pm »

To my mind its Green Chromatic Aberration, but I may be wrong.

Hard to say, but it may be a case of Longitudinal Chromatic Aberration (usually with Magenta and Green defocus on opposite sides of the focus plane), instead of Lateral Chromatic Aberration (usually Red and Blue) on opposite sides of high contrast edges. Purple fringing can be caused by cross-talk between photosites, usually at higher exposure levels.

Quote
I fixed it with a layer mask and color editor adjustment with big -Sat selected, just painted it out with the mask brush. Luckily I can get away with that here. Much rather there was a 'green fringing' slider in C1 though.

The Advanced Color Editor allows creating a mask based on a selected color (e.g. sampled from a green fringe). All you need to do next, after inspecting/tweaking the mask, is dialing in either desaturation or replacing the Colorbalance by one shifted to the opposite side of the color circle for a full Adjustment layer. It may not be sufficient, because the Chromatic Aberation color blends with other colors, but one can duplicate the adjustment layer and mask.

Cheers,
Bart
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narikin

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Re: Correcting *Green* Chromatic Aberration in C1 - what options?
« Reply #4 on: March 13, 2019, 06:06:43 pm »

The Advanced Color Editor allows creating a mask based on a selected color (e.g. sampled from a green fringe). All you need to do next, after inspecting/tweaking the mask, is dialing in either desaturation or replacing the Colorbalance by one shifted to the opposite side of the color circle for a full Adjustment layer. It may not be sufficient, because the Chromatic Aberation color blends with other colors, but one can duplicate the adjustment layer and mask.

Cheers,
Bart

That's what I suspect also: Longitudinal CA.
And yes, what you suggest is what I did, use the advanced color editor, pick the green, and retouch it out.  Thanks for confirming though.  This can be done easily in this image taking it to neutral/white is invisible repair. Might not work with another situation.

I was just hoping there was some quicker/easier way, like there is in Lightroom, with its Green CA slider. Seems not. Maybe worth putting a feature request into Phase One for this in future release?

Thanks again.
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Bart_van_der_Wolf

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Re: Correcting *Green* Chromatic Aberration in C1 - what options?
« Reply #5 on: March 13, 2019, 11:36:20 pm »

I was just hoping there was some quicker/easier way, like there is in Lightroom, with its Green CA slider. Seems not. Maybe worth putting a feature request into Phase One for this in future release?

Requesting a feature enhancement wouldn't hurt. Make sure to mention Green/Magenta Longitudinal Chromatic Aberration correction.

Cheers,
Bart
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