[Guest]

In real life there is a big difference: if corners are blurry, they are blurry. Like the extreme corners of my(the) EF 35mm f2. If there is some field curvature, chances are there is something sharp in corners, because a scene usually is deep (3D).

Can you give examples where the field curvature from that lens gives you problems? Which focal length?

When I look at image samples taken with that lens, I only notice the CA in the corners, CA which is easily corrected.
<a class="bbc_url" href="https://pixelpeeper.com/lenses/?lens=13192">https://pixelpeeper.com/lenses/?lens=13192</a>

A typical example would be a landscape with mountains (to have details in the upper corners at infinity), or even an architecture shot of a large flat building at some distance.


Several copies of the 15-85 that I tested, including my own, produce very blurry corners in that case. Worst is at about 24mm, but 15mm is almost as bad. The problem is much less pronounced at distances up to 5m; that's why I did not detect the problem in my chart tests after buying the lens.


Correct focus is critical too. If I simply rely on center focus of my 40d at WA settings, the corners are heavily blurred. I believe that slightly inaccurate focus, decentering, and field curvature add up.


I discarded most if not all of the really bad examples, but will check in my Trash as soon as I am at the right computer again.