Somebody changed my thread title, I think. Interesting, and more accurate now as-is for what the thread turned into. So speaking of focus problems...
I got the lens from John. I had a chance last night and this morning to rattle off maybe 30 or 40 shots with it in different situations, and I've got something erratic that I could use help figuring out. There's something going on with center sharpness sometimes being VERY soft compared to the corners. It isn't focus, either, because corner objects at the same distance (hundreds of feet away) are crisp while center objects are fuzzy. And then in other shots, everything is perfectly acceptably clear. My first thought was "f stop" but I haven't been able to make that theory work yet. Some examples...
Here's a shot where the center is fine. Bright light, focus distance of maybe 50 feet, please feel free to dig through the exif info...
DSCF1748 by
gordopuggy, on Flickr
And a center crop. I'm fine with this level of sharpness from this tiny lens:
DSCF1748center by
gordopuggy, on Flickr
Ok, now onto the more problematic stuff. I did 7 shots in a row of the same scene, testing out my presets. When I viewed all 7, they were fuzzy as all getout in the center.
Full shot:
DSCF1760 by
gordopuggy, on Flickr
Crop from center... bad bad bad:
DSCF1760center by
gordopuggy, on Flickr
Crop from far right... much better. What the hell?
DSCF1760right by
gordopuggy, on Flickr
The lens is CAPABLE of being wonderfully sharp. Here's a full shot at 2.8:
DSCF1772 by
gordopuggy, on Flickr
...and the center crop. This is fantastic for wide open:
DSCF1772center by
gordopuggy, on Flickr
And finally another longer focal length shot, with a nice crisp center.
View attachment 20444DSCF1775 by
gordopuggy, on Flickr
View attachment 20445DSCF1775center by
gordopuggy, on Flickr
So if anyone can explain that, I'd be thrilled.