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 ...
On occasion, the auto-focus system in my camera and/or lens just stops working. I'll be holding down the shutter release halfway and tracking a subject and I can feel/hear the auto-focus system ...