Test lens

[iaperturez]

I'm going to buy a brand new Sigma 50mm f1.4 lens. But heard a lot ppl say that the sigma lens got front & back focus problem. I have no idea how to test. Any experts here to share the methods of testing the lens in the shop when buying the lens.

 

[Octarine]

Please do yourself a favour and use the Search function, upper right hand. Topic has been discussed in detail multiple times, just recently here:
http://www.clubsnap.com/forums/showthread.php?t=707094

 

[pokiemon]

yep. read the link octarine has sent to you. if you still dont understand how it works, post your questions here!