Opticallimits

I bought a sigma 10-20mm f/4-5.6 lens for my canon a couple months ago.



It seems to never be quite as sharp as I would like, not outrageously soft but enough to nearly always think it could be sharper, perhaps ive just been spoiled by my 50mm 1.8 prime. Its not just the focus, ive played around going between auto/manual.



Before I go sending it in for sigma to take a look I would like to hear advice, is there any way to give it a solid test for softness/sharpness? Maybe someone has a trick, a particular thing to take a picture of. Its hard without having two of these lenses side by side.



Thanks for any advice/input

Have you tested it for front/back focus? There have been e number of articles in this forum describbing how to. I bought a piece of equipment from Datacolor called "Spyder lens Cal" to check for front and back focus and it works really well. I highly recommend it.