Sigma 30mm f/1.4 back focus issues

gl600 · Jan 30, 2010

Hey,
I just bought a new Sigma 30mm f/1.4 lens and it has some significant back focusing going on.

Should I send it back and get a new one or send it to Sigma to get calibrated? (would Sigma charge for that?)
What are your experiences with getting a new lens that either front or back focuses?
Thanks

Overread · Jan 30, 2010

Sending it in for calibation/correction whilst its still under warrenty would be the best option. I know that canon and nikon will do camera lens calibrations but I am unsure about sigma. Also for camera lens calibration you also have to send your camera in as well (since like lenses cameras also have slight differences in manufacture - which is why sometimes a lens which is soft or has focus issues on one camera can have no such problem on another camera body of the same make)

Big Mike · Feb 1, 2010

I've got that lens and mine also has some focus issues. I've thought about sending it in...but Sigma doesn't have a Canadian service centre and instead refers us to some other company.

giorgio · Feb 1, 2010

Hi 'all

Sorry, but, what exactly is back of front focusing?

Big Mike · Feb 2, 2010

Sorry, but, what exactly is back of front focusing?

It's when the accuracy of the Autofocus is off. If it's front focusing, the actual point of focus will be closer to the camera than the spot that you focused on.
For example, if you put the AF sensor point on a person's eye and use the AF, you would expect the eye to the sharpest part of the photo, especially if you are using a shallow DOF. But if the lens is front focusing, then the nose might be sharper than the eye.

giorgio · Feb 2, 2010

Big Mike said:
Sorry, but, what exactly is back of front focusing?

Click to expand...

It's when the accuracy of the Autofocus is off. If it's front focusing, the actual point of focus will be closer to the camera than the spot that you focused on.
For example, if you put the AF sensor point on a person's eye and use the AF, you would expect the eye to the sharpest part of the photo, especially if you are using a shallow DOF. But if the lens is front focusing, then the nose might be sharper than the eye.