I recently purchased a Sigma 24-70mm f2.8 lens which I am using on a Canon 40D body. Around 8 of 10 shots were soft, regardless of subject matter. Exposure, white balance etc. all looks fine. I only ...
I got this Sigma DC 18-50mm f/2.8 EX MACRO HSM lens few weeks ago, but I noticed considerable sharpness problems with wide apertures. Until f3.5 (or even f4.5) this lens can't really be used. I would ...