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Sigma 105mm f/1.4 DG HSM Art on Nikon D850: Substantial Color Shift Going from f/1.4 to Other Apertures

Get Sigma 105mm f/1.4 DG HSM Art and Zeiss Otus B&H Photo. See also my Canon wish list and Nikon wish list and Zeiss lenses for DSLRs wish list.

How timely for subscriber Chris R to write (in general) about the color rendition of lenses. In this case, the color changes with the same lens wide open versus stopped down—one need not compare to another!

I had wondered why I had to give the portrait examples such individual attention; the color seemed to vary a lot. As it turns out, the lens itself was responsible, with f/1.4 having a very different color rendition (on the Nikon D850) than at other apertures.

...

Scene at f/1.4 and f/2 (toggle), processed with identical raw conversion settings
f1.4 @ 1/1600 sec, ISO 64; 2018-07-09 17:33:28
NIKON D850 + Sigma 105mm f/1.4 DG HSM Art

[low-res image for bot]
DataColor SpyderCHECKR

Below, toggle to compare. Why does the f/2 frame have a sickly yellow-green color as compared to the f/1.4 frame? I explore the behavior in meticulous detail.

Sigma 105mm f/1.4 DG HSM Art: Color Shift with Stopping Down, SpyderCHECKR Card

An about $127 DataColor SpyderCHECKER was used for the above evaluation. I use the clamshell version so I can safely carry it without damaging it. I do not use the calibration software as I have not been satisfied with the results versus the stock Adobe profiles.

Field examples prove out the findings:

Sigma 105mm f/1.4 DG HSM Art: Color Shift with Stopping Down, Field Examples

The above pages are essential, practical and useful reading for anyone shooting the Sigma 105mm f/1.4 DG HSM Art, as well as other lenses. Exact figures for how to compensate in Photoshop/ACR are given for two examples and there are other field examples also.

This is not the first lens / first time I have seen such color/tint changes stopped down from full aperture. An open question is whether sensors other than the one used in the Nikon D850 will exhibit the same or less or more of this color/tint shift. As an aside, it also raises the issue of how MTF is tested, namely the spectral weighting.

The color difference below is obvious, at least to those with discriminating color vision. Toggle to compare.

Scene at f/1.4 and f/2 (toggle), processed with identical raw conversion settings
f1.4 @ 1/1600 sec, ISO 64; 2018-07-09 17:33:28
NIKON D850 + Sigma 105mm f/1.4 DG HSM Art

[low-res image for bot]
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