Greetings, fellow CL members! I think the older ones haven't heard from me in a while and the new ones haven't heard of me at all! Haha, just kidding. I'm not that old.
Here are some crops from multiple photos of the same scene with exactly the same viewfinder-framing
(tripod mounted, not moved) taken with the Sony A200 + SAL 1870 lens at 18mm (widest setting). Differences are in exposure value (sorry, by accident), aperture value
(intentional), and shutter speed (to keep exposure value similar). More details below.
Purpose of this is to test the sharpness of the Sony DT 18-70mm lens at various aperture values while at its widest focal length setting of 18mm.
The photos were taken on 11:26pm at night with the only light source being a single circular fluorescent light ('diffused' by translucent plastic cover) on the ceiling above.
This is the main scene photographed, uncropped. (f/6.3, 2") 1024 x 685
These are the crops placed in one image. 1024 x 743
1st column from the left is the Top Left of the photo.
2nd column from the left is the Centre Left of the photo.
3rd column from the left is the Centre of the photo.
4th column from the left is the Centre Right of the photo.
TOP TO BOTTOM (horizontal rows): f/3.5, f/11, f/22
1) Centre sharpness is rather similar throughout, differences (if any) are not very discernible to me.
2) Corner sharpness is best at f/11, with most DOF at f/22, and pretty crappy at f/3.5.
3) Chromatic aberrations (CA) seem to get lower with narrower apertures.
4) Overall sharpness is best at f/11.
PLEASE NOTE: Only f/3.5, f/11 and f/22 have been tested at 18mm for this lens.
My apologies: Photos get darker as the aperture goes wider (due to poor metering on my part?).
As I am now having my slightly-packed-with-activities mid-year school holidays, I will try to find more time to test this lens on my camera at different settings on various subjects.
If you would like to see max. resolution crops, please reply here or PM me.
P.S. to Moderators: Hope I've kept to the new rules which were introduced while I was away! Maximum 1024 pixels on longest side if there only are a couple of photos. (I assume the 2nd collage is considered as one image)