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Pentax K1: that Scratch from Sigma Lenses

See my Pentax K1 wish list at B&H Photo.

Mark N writes:

Thank you very much for your in-depth examination of the Pentax K-1 camera.

I noticed that you used the Sigma 35mm f/1.4 DG HSM Art lens with the K-1 to take the Super Resolution Mode of the Dolls. I am waiting for my K-1 and plan to use that lens as well. Sigma has just announced a warning not use this lens with the K-1 because it might scratch the lens mount. Did you have any problems when you ran your tests?

DIGLOYD: yes, the Sigma 35/1.4 DG HSM Art is available in Pentax K mount at about $899, and it is a very fine lens, much better corrected than the Pentax prime lenses in that range. And so, a must-have lens for the K1. Optically, the about $1000 Pentax smcP FA 31mm f/1.8 Limited is not in the same league as the Sigma 35/1.4, a fact driven home trying to focus the two in magnified Live View: the Sigma is relatively crisp at f/1.4, the Pentax 31/1.8 a hazy affair, the Pentax apparently being a classic feel-nice lens, not a performer in any technical sense. The Pentax 31/1.8 is beautifully built, but it certainly is Limited (in performance and value).

The Sigma 35/1.4 mounts just fine on the K1 with no resistance or noise or any apparent issue at all, and that is the problem; one might never notice that mounting the Sigma 35mm f/1.4 DG HSM Art onto the K1 engraves a thin cut into the camera body just above the lens.

The other issue is that the K1 defaults to APS-C crop with the Sigma 35/1.4 DG HSM Art. That is easy to work around—just set the camera to full frame explicitly (not Crop = Auto).

Shown below is the 2mm scratch caused by mounting the Sigma 35mm f/1.4 DG HSM Art onto the Pentax K1. Other Sigma lenses might cause deeper and/or wider scratches.

Scratch on Pentax K1 body caused by Sigma 35mm f/1.4 DG HSM Art
f2.2 @ 1/10 sec, ISO 100; 2016-05-16 21:20:04
iPhone 6s Plus + iPhone 6s Plus back camera 4.15mm f/2.2 @ 29mm equiv (4.2mm)

[low-res image for bot]
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