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Samyang 14mm f/2.8: Lens Skew Asymmetry

In DAP, I present a study of the lens skew (asymmetry) seen with the Samyang 14mm f/2.8. Every brand that I have used has at one time or another manifested a lens skew issue, but this example is particularly instructive.

Because it is of general interest, it is also cross posted as a case study of lens skew in Making Sharp Images.

Get the Samyang 14mm at B&H Photo. Available in regular and cine mount.

Asymmetric optical performance (focus variance)

Florent C writes:

I've read your lens skew issues report with the Samyang 14mm f/2.8 and I would like to share my experience. I've had 3 samples of this lens, all purchased new from trusted vendors, and suitably packed.

The first one, for my 5D II, suffered very severe lens decentering, so a full left portion of the frame was completely blurry (noticeable at screen size), while the right side was sharp. I have a hard time believing this happened during transport, but maybe it got worse with it.

The second sample was fine optically wise, but after a few days of normal use, the aperture ring showed some odd play. I had to tighten a screw to make it back to normal again.

Then, I bought the lens back for my D800E. There was a lens skew issue, much less severe than with my first sample, but easily noticeable when examining the pictures.

Ouch.

Regarding build quality, Roger Cicala says something interesting about what's inside:
“I will note, this is held together inside with plastic, glue, and small screws. You won’t be using it for years”.

To be fair, one can buy a few samples of this lens and still not reaching the price of a Zeiss 15mm f/2.8. But now, I'm considering the Zeiss.

DIGLLOYD: it seems that the sample I used was better than average.

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