I recently purchased the new DA*11-18 lens and decided that I would test for any de-centering. I have never done this before so with the help of the internet I found a process for performing the test.The following is the process I used, the camera and lens settings, and the results.
Settings
Camera - K3 mounted on tripod
Exposure - Manual (Spot metered on the center of target on first (center) exposure)
Focus - Manual
Shake reduction - Off
Aperture - 2.8
Focal Length - 11mm and 18mm
Shutter speed - As need for correct exposure
ISO - 100
Process
Set the focal length to 11 mm. Positioned camera so the target (building about 120 yards away with sign"FISH CAMP") was in the center of the view finder. Focused on the "FISH CAMP" sign and adjusted shutter speed for proper exposure. Turned on the Focus Clamp (neat option on this lens) to ensure focus did not change between exposures. Took the first exposure using a remote shutter release in the mirror lock up mode. Loosened the tripod ball head and moved the camera so the target was in the upper left of the viewfinder. Tightened the ball head and made the second exposure. Repeated this for the other three corners. Changed focal length to 18 mm and repeated the whole process.
The attached images are 100% crops of the images. The top is the 11mm set and the bottom the 18 mm set. These are straight out of the camera images with no adjustments made. The only thing I did was crop them and make a collage in photo shop of the two different focal lengths
My observations - Upper left is the softest wth the bottom right the sharpest (There was a significant wind so don't look at the trees). Appears to have a little more vignetting on the top corners as compared to the bottom corners (top corners are darker than bottom corners). There is a little chromatic aberration in all four corners but could easily be corrected. CA on the 12-24 is much worse.
Since I have never done a de-centering test before was this the correct process and if so is this an acceptable lens regarding focus de-centering? I believe it is but for the price of the lens I just wanted to get a second opinion. Even though you want it to be there is probably no perfect lens.