Warranty repair/adjustment completed
The SIGMA AF 10-20mm f/4-5.6 DC EX was submitted by to SIGMA Corp for repair on December 13th, 2008. It returned, today (January 9, 2009).
I then did a check to see how it measured up to the last set of images I took, comparing it. This was a tripod shot, using the A100 ... and the only item changed was the lenses. I initially set my exposure with the SIGMA ... thinking a good f/5.6 would be f/5.6 throughout the shoot. Unfortunately, not really ... apparently the manufacturer's must have some disagreement here ... because although I did nothing to the lighting, the exposure sure changed, as I swapped lenses. The TAMRON & KM shot a lot brighter, by almost a full f-stop. They actually look over-exposed ... and remember, this was a "manual shot" (M-mode) ... all settings fixed.
Here they are ... with a surprise or two @ 18mm - f/5.6 - ISO 100 - External flash set on TTL - EV=0 - FV=+1 - Manual Mode - Dsitance to subject: 10-inches
SIGMA AF 10-20 4-5.6 DC EX
Konica-Minolta AF 17-35mm f/2.8-4 "D"
TAMRON SP AF 17-50mm f/2.8 XR Di-II LD Aspherical (IF)
TAMRON AF 18-250mm f/3.5-6.3 ZR Di-II LD Aspherical (IF)
The real surprise is the comparison shot with the TAMRON 18-250mm f/3.5-6.3 lens. The "Utility Lens" turned in some excellent results ... and once again, renews my faith in its ability to deliver. A truly super "all-around" lens.
Anyway, just for review: Here is the initial SIGMA AF 10-20mm f/4-5.6 DC EX O-O-T-B shot to caused my concern and sent the lens off for manufacturer's warranty adjustment.
The focus has definitely been improved to acceptable standards.