Zeiss 21mm f2.8 ZF.2 color cast on D3x

Started Mar 12, 2010 | Discussions thread
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Paul Richman
Paul Richman Veteran Member • Posts: 3,793
Zeiss 21mm f2.8 ZF.2 color cast on D3x

Have you found a way to eliminate the cyan/blue cast this lens gives to the corners? If so, would you mind sharing with us?

I've tried Lloyd Chambers method, but it does not work for me. Here's what I did. I started with this RAW file, which I processed in LR using the following settings there:

LR (ACR) Settings:

Temp: 6300
Tint: -8 (both determined by WB-tool clicking in the center of the image)
Exposure: +0.46
Blacks: 42 (well before black clipping would occur)
Brightness: +1

CA (Red/Cyan): -10
Lens Corrections:
Amount: 26
Midpoint: 0

Note that this was a completely overcast scene, so no blue/cyan from the sky. (Of course, I completely fixed this file for my own use by just completely desaturating blue/cyan in ACR, but this does not work for many other images.)

I then created a mask that should have eliminated the cast, following Lloyd's procedure. With this lens on my D3x set at f10 and +1EV, I shot my Eizo 30" calibrated screen with an image in CS4 that I created to give similar WB.

This image was created as follows: 3000x2000 pixels with (200,200,200) RGB, and then over-layed it with a Color Balance layer set to Highlights 0, 4, 80. This CB setting was determined experimentally, by taking many shots and processing them in LR attempting to duplicate the WB of the above shot.

I imported this shot into LR, copied the settings from the above image and pasted them into this image, and took WB from the center of the result. The WB was 6350 and -5. This was as close as I could get to the 6300 -8 of the above image, after many iterations.

I opened this into CS4, and followed Lloyd's procedure. Gaussian blur +20, convert to LAB, create a new layer from background, set Blend Mode to Overlay with just "a" and "b" channels selected etc. Dragged this mask onto my image (holding shift key down to center the new layer). Here's what I got:

It's better, but still not nearly corrected. Note that Lloyd's procedure calls for inverting the "a" and "b" channels of the mask layer, which makes sense, but doing so made things worse, not better, so I didn't do that.

There's my saga. Can you help? It would be much appreciated. This is my only gripe against this otherwise stellar lens, so a good solution would make me very happy.
Paul Richman

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