Is this lens decentering? - Rokinon 14/2.8

I finally did a sharpness test and I am worried that my lens has decentering... this was a photo taken of my home library from about 6 feet away. Manual focus @ F2.8, on a tripod, leveled, etc. The UL and UR seem to be blurry relative to the center, LL and LR. All images are shot in RAW on a 6D, SOOC, no corrections whatsoever.

Does this look unusually bad? This is my first UWA but everything I have read is that the Rokinon 14/2.8 has very good sharpness across the entire field, so I am wondering if my copy is below average.

Should I exchange the lens for another? Thanks!

Full Frame:

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By your main photo you are not square to the wall of books. Your focus is a tad off and not by much.

Hmmm.. I tried to align things as best as a could by eye.. maybe I need to measure the right side and left side of the camera to the wall using a tape measure. I'll try again tonight. Thanks for the suggestion.

While I want to make sure I have a good copy of a lens that appears to have significant copy to copy variation, sometimes I wonder if I should just crop the corners off and call it done.

Scrumhalf wrote in post #16738949
Hmmm.. I tried to align things as best as a could by eye.. maybe I need to measure the right side and left side of the camera to the wall using a tape measure. I'll try again tonight. Thanks for the suggestion.

While I want to make sure I have a good copy of a lens that appears to have significant copy to copy variation, sometimes I wonder if I should just crop the corners off and call it done.

Much of the light appears to be coming from the right side, based on the bright sheen I see on many of the books. See if you can shoot something with more even lighting across the whole image.

I agree with Talley. Your composition isn't perfect and using a tape measure isn't going to help you with the error you made in this photo. Look at the distance of the top shelf to the top of the image frame, and bottom shelf to the bottom of the image frame. Now look at the difference between the left and right sides. You took the picture at a slight angle to your bookcase. Shooting this at f/2.8 gave you the worst depth of field to determine if there is a focus problem. To test for decentering, put your lens out of focus and photograph points of light. If the bokeh of the points of light is asymmetrical like ovals or egg shapes, then you have a decentered lens. If it's like the aperture blades are supposed to make it, then there is no decentering problem.

Considering depth of field at f/2.8 I would guess your copy is fine actually. But let's make sure. Instead of taking a photograph at the aperture that is going to give you the worst depth of field, take another one at f/11 and then see if that overcomes error in composition if you can't align it perfectly in the viewfinder.

Thanks for the suggestions. I plan on doing some more shooting this weekend with it. I'll keep your inputs in mind!