How did I do the reviews?

Calling my simple tests "reviews" may be a bit much. What I did is pretty simple, I chose a distant subject (the view out of my living room window…) and took pictures at various focal length (for the zooms I took care to match the focal length to the one of the fixed focals). You have views taken at the center (the street) and views taken at the extreme bottom left corner (the newsstand). For the corner view, I simply rotated the camera to put the newsstand on the extreme corner of the frame. Depending on the focal length, I needed to rotate the camera a lot (wide-angle) or just a little (tele). This are the corresponding zones on the 50mm test picture:

Center crop first:

Bottom crop:

(Notice that the camera has moved for the corner crop)


Each picture is 800x600 pixels, in the review pages you just need to click on it to see it at pixel level or download it.

These pictures are a bit bigger than the ones you may be used to. There is a reason for that: for corner performance, one wants to know how far the unsharp zone extends. The extreme corner is on the bottom left, the top right is closer to the center of the picture. For a lens like the CZ 16-35 where only the extreme-extreme corner is unsharp at some focal lengths, this is a useful information, and one which you won't find on test simply stating "corner performance".

For each lens, I made sure that the published corner is not noticeably worse (or better) than the other 3 corners. For most lenses there are some differences between the corners: no lens is perfectly centered and examining the picture at the pixel level like here exaggerates these tiny differences, but when the differences were too big, I declared that the lens was malfunctioning and did not publish the data.

All tests are done with the Sony full frame 24.6mp Alpha 900. Please keep that in mind when judging corner performance if you use an APS-C camera.