12mm f2.8 7Artisans results

Anyone here have this lens?

What I found when photographing a flat wall:

(The center is sharp on all tests)

With focus set to 9 feet (distance to the wall), right side was out of focus, left side is quite sharp.

Set to 5 feet the right side improves.

Set to 4 feet - both sides slightly soft.

Set to 3 feet the right side is sharper than the left.

MY QUESTION for users:

Should I order another or is this an inherent design issue - i.e. field curvature?

How sure are you that your sensor plane was parallel to the wall?

Your results appear to indicate a decentering issue rather than field curvature.

Thanks for the response.

I measured the distance from the camera to both the very left and right side of the wall included n the field of view. Camera leveled on a tripod.

Wall was only 12 feet wide, hence the camera 9 feet away.

Am thinking of finding a warehouse or other wall where the camera can be placed further away but as my intended use includes interior shots I wanted to test in an actual setting.

Most likely decentering. These lenses are so inexpensive that it should be expected that they have flaws. If not decentering it may be something else.

You could order a handful and cherry-pick the better one - and return the rest.

Agreed the results primarily indicate de-centering, all the (reputable) reviews note that whilst the lens exhibits a sharp centre, the edges only become sharp when the lens is stopped down, so, I think that any subsequent testing should note a range of different Apertures, not just a range of different Subject Distances, that will better allow evaluation in regard to the lens's suitability for your purposes.

WW

Any side-to-side variation in image quality indicates decentring.

The clincher is to rotate the camera upside down with the same subject, focus and framing. If the defect changes sides when the image is viewed right-way-up, then you have a decentred lens.

I got through 3 Samyangs that were returned due to decentring. One so bad that you could clearly see through the viewfinder that the left side was OOF while the right side was sharp. It's just careless assembly.