The Tamron 17-50/2.8 Di2 is known to have very good borders resolution but…

If you take this lens close to the flat subject, parallel to lens and take a photo at distance below 1 meter you will see strange things in the corners. The pictures below are 100% crops from left bottom corner, taken at 50mm, distance ~0.6m, camera on tripod.

f2.8:

f4:

f5.6:

f8:

This problem gets bigger the more you close to minimum focusing distance (0.27m). If you go away around 1m or more it starts to disappear. This issue is explained in this test. As you can see it’s all about focus plane curvature.

“On the downside the extreme corners showed a very strong degree of field curvature at 17mm and a little less so at 24mm. This means that the focus plane isn’t flat but it bends towards to corners. As a consequence you will end with out-of-focus corners when shooting flat or very deep objects at large aperture settings (…). The problem will be reduced when stopping down thus increasing the depth-of-field around the curved focus plane.”

For me Tamron is a great lens anyhow. Check out a comparison of Tamron with Konica Minolta 50/1.7.

This entry was posted on Saturday, April 19th, 2008 at %1:%Apr %p and is filed under Konica Minolta, Sony. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.