Samyang 12mm F2 infinity focus issue?

Started 8 months ago | Questions thread
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SimonB93 Contributing Member • Posts: 680
Samyang 12mm F2 infinity focus issue?

Hi Guys,

A few days back I bought a second hand a6000 for cheap and today I received my Samyang 12mm F2 to compliment my rx10 for landscape shooting.
I mode some quick test shots to check the lens and I noticed something that isnt right IMO. The lens had no issue rendering sharp images on nearby subjects, but I have a feeling it doesn't do as well as it should when focussed to infinity at smaller apertures.

To check where the true infinity point of this lens is I shot 5 images with the focus against the hard stop of the infinity symbol and 5 shots with the focus ring turned slighty back a notch.

At F2, F2,8 and F4 the images focussed slightly back of the hard infinity stop are clearly sharper then the ones against the hard stop.

Against the hard stop, F2

Slightly before the hard stop, F2

Against the hard stop, F2.8

Slightly before the hard stop, F2.8

Against the hard stop, F4

Slightly before the hard stop, F4

So far nothing special, for these apertures the true infinity is slightly before the hard stop. This is also the case for F5.6 although the difference is getting smaller.

Against the hard stop, F5.6

Slightly before the hard stop F5.6

At F8 sharpness on both focus positions is quite similar, the image at the hard stop might be slightly sharper.

Against hte hard stop, F8

Slightly before the hard stop, F8

The problem is that neither of the images at f8 (and f5.6) are sharper then the images at f2 and f2.8 which you would expect them to be, instead they're slightly softer for as far as I can see.
What could be the reason for this?

 SimonB93's gear list:SimonB93's gear list
Sony Cyber-shot DSC-RX10 Sony RX100 IV
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