weird Sigma 12-24 f4.5-5.6 DG behavior with 7d and other bodies , help

Started Jan 20, 2013 | Discussions thread
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mantra Contributing Member • Posts: 776
weird Sigma 12-24 f4.5-5.6 DG behavior with 7d and other bodies , help


i own 12-24 4.5/5.6 DG EX HSM model I (HSM should like canon usm ,should not it? i mean i can rotate and move with auto af on ?)

and i tried on my 7d and on other bodies like 5d mark 2 , 30D and 20D

the weird thing is the focus ring , i doesn't stop every time at the same spot

i mean for example

i set my camera on a tripod manfrotto set the camera and a remote shutter

well i tried to focus on a tree

and i did notice that  focus on the tree and  move back the focus ring at 0.28 and refocus , the focus ring doesn't stop on the same stop for example it stops sometime @ 1.5 or 2 or even to infinity

this happen not only at 12 but even at 24

i tried to focus manually with the bip but the focus is not spot on

the only way is to use the live view

but is it normal?

i mean at such focals the images should be sharp even the focus is not spot on

i mean it's not a 70-200 2.8 or a 24-70 2.8 or a fixed lens like a 50 1.4

please could some help me?

maybe share with me your experiences



 mantra's gear list:mantra's gear list
Canon EOS 5D Mark II Nikon D700 Canon EOS 5D Mark III Canon EF 50mm f/1.4 USM Canon EF 85mm f/1.8 USM +9 more
Canon EOS 20D Canon EOS 30D Canon EOS 5D Mark II Canon EOS 7D
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