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Author Topic: Magenta Fringing - Sigma DP2 Quattro  (Read 6595 times)

dumainew

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Magenta Fringing - Sigma DP2 Quattro
« on: June 27, 2015, 04:24:12 pm »

Hello All,

Not sure exactly where to post this so I thought it could start here.

The problem is the magenta fringing that's still present after processing it both in Sigma's proprietary software and then again in ACR.
The magenta is most visible along the strands of Spanish Moss in this crop.
Took this foto at ISO 250, f8, 1/100s, neutral color setting, Raw file, Bit depth 16, Res.: High, color mode RGB, ProPhoto color space, Exposed for the brightest areas.
Any suggestions for how to rid these remnants of magenta will be most appreciated.

Thanks for looking.
Richard
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hugowolf

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Re: Magenta Fringing - Sigma DP2 Quattro
« Reply #1 on: June 27, 2015, 08:32:15 pm »

If there are no areas that are supposed to contain magenta, then just use Ps Hue and Saturation with the dropper to select and limit the range of the selection.

If there are areas where you want to retain magenta, use a Hue and Saturation layer with a layer mask to selectively paint only the areas where you want magenta.

Brian A
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dumainew

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Re: Magenta Fringing - Sigma DP2 Quattro
« Reply #2 on: July 01, 2015, 01:33:12 pm »

Hi Brian,

Thank you very much for your help. I eventually used H&S to make local adjustments and the most obvious fringing is now gone. However, one question remains: in a high frequency file, is there 'micro' fringing going on that subtly but surely gives a color cast? With the file in question, it turns out it was red fringing, not magenta fringing, according to the eye dropper sampling. If I make a global adjustment, removing red everywhere, won't that 'cool off' the foto ?

Thanks.

Richard
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hugowolf

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Re: Magenta Fringing - Sigma DP2 Quattro
« Reply #3 on: July 02, 2015, 12:58:54 am »

Thank you very much for your help. I eventually used H&S to make local adjustments and the most obvious fringing is now gone. However, one question remains: in a high frequency file, is there 'micro' fringing going on that subtly but surely gives a color cast? With the file in question, it turns out it was red fringing, not magenta fringing, according to the eye dropper sampling. If I make a global adjustment, removing red everywhere, won't that 'cool off' the foto ?

It really depends on how much you can limit the red hue that you are desaturating to just the red you want to get rid of. When you select a hue, rather than doing a global desaturation, there are two sets of sliders. The inner two restrict the range you are dealing with, the outer two are analogous to feathering.

If the range of reds is too broad and is affecting areas you don't want desaturated, then you need to do it on a duplicate layer with a layer mask or a hue and saturation layer. You can then 'paint' only the areas where you want to get rid of the red.

There are two sorts of layer masks: Reveal All and Hide All. With a reveal all mask, you see the affects of global desaturation, and using a black brush, you can erase and areas you don't want affected by the adjustment. With a hide all layer mask, you see none of the adjustment but can paint it in to any areas you want using a white brush. You can even use a gray brush to remove or gain only some of the adjustments made on the layer.

If you use a Hue and Saturation adjustment layer, then you automatically get a reveal all mask, and a black brush will remove adjustments. This is if you want the adjustment in most areas and only want to remove it in small areas. With the layer mask selected, Ctrl+I (Cmd+I on a mac) will switch the mask from Reveal All to Hide All.

https://helpx.adobe.com/photoshop-elements/using/adjusting-color-saturation-hue-vibrance.html.

There should be plenty of tutorials on using layer mask to paint in adjustments on the web if you do a search.

Brian A
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Isaac

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Re: Magenta Fringing - Sigma DP2 Quattro
« Reply #4 on: July 02, 2015, 12:10:13 pm »

Took this foto at ISO 250, f8, 1/100s, neutral color setting, Raw file, Bit depth 16, Res.: High, color mode RGB, ProPhoto color space

Could you post a raw file somewhere accessible? (Oh! Sigma Quattro! Never mind.)

Attached RT Defringe used on jpg.
« Last Edit: July 02, 2015, 12:12:45 pm by Isaac »
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dumainew

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Re: Magenta Fringing - Sigma DP2 Quattro
« Reply #5 on: July 05, 2015, 02:12:20 pm »

Thanks Brian and Isaac.
I got it gone now.
The DP2 Sigma is a challenge to use, definitely, but with a lot of patience it's pretty remarkable.
Richard
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