Camera Labs

Probably going to buy a Sigma 30mm f1.4 lens in a bit. There are some reviews describing some focusing short. What's the best way to check the one I'm looking at doesn't?

Ian

_________________
Canon EOS 550D (with Magic Lantern)
18mm - 135mm Kit Lens, 50mm f1.8, Sigma 30mm f/1.4 EX DC HSM
430EX II Flash with Phottix Strato Wireless Tigger Set
Manfrotto 190CXPRO3 with 496 Ball Head. Gorilla Pod SLR
Canon Powershot A720IS with CHDK and intervalometer script. Pentax Optio W90

My Blog - http://www.ianganderton.wordpress.com

My suggestion is: Put the camera down on some surface with a fixed distance to some object. Use manual focus in live view to get the center of the frame in perfect focus. Then exit live view and half-press the shutter to focus on the same spot with the traditional phase-change system. If the focusing distance window on the lens changes, the lens has front- or back focus

_________________
Canon DSLRs: 5D Mark III, 7D
Canon lenses: 17-40/4L, 24-105/4L, 24/1.4L II, 50/1.4, 85/1.8, 100/2.8L Macro, 70-200/2.8L IS, 100-400L
Other stuff: Canon 580 EX II, Canon 430EX II, Velbon Sherpa 600R
Apple: MacBook Pro 15", iMac 27", iPad III, iPhone 4S, Apple TV

My deviantART

don't just AF on the center,because the middle AF point is cross-type & that might influence the overall AF perfomance & precision of that lens. always try many focusing scenarios.
A Tamron 17-50mm that I tested failed completly (well it had serious front focusing issues),but only after I used all AF points,the middle AF point was much more accurate then the others. Focusing with the non-cross type points resulted in some looong hunting. (outdoors!)

_________________
Gear: Nikon D80, 18-105mm, 35mm F/1.8, 85mm F/1.8, SB-600
Visit my work here

Try micro digital in Mall of the Emirates (first floor, above French Connection)

They sometimes have a selection of certain Sigma lenses so you may be able to try two copies. They'll give you a 10-15% off 'best price'

Normally the light isnt great in the store, but try close focussing on an angled advert/point of sale sign at a particular letter wide open or close to it.

Good point on the cross-type sensor, Razvan

_________________
Canon DSLRs: 5D Mark III, 7D
Canon lenses: 17-40/4L, 24-105/4L, 24/1.4L II, 50/1.4, 85/1.8, 100/2.8L Macro, 70-200/2.8L IS, 100-400L
Other stuff: Canon 580 EX II, Canon 430EX II, Velbon Sherpa 600R
Apple: MacBook Pro 15", iMac 27", iPad III, iPhone 4S, Apple TV

My deviantART