Sigma 18-50mm f2.8 - do I have a bad copy?

richmoffitt

I am pretty sure I know the answer, but I'm looking for a little confirmation. Would the general community here agree that the following photo exposes a flaw in the lens?



I'm wondering if this looks severe enough to merit a warranty claim.

Thanks!

ziggy53

It appears that the lens is misaligned and there is a strong shift in focus left to right. If you just purchased the lens and if you purchased from a reputable source I would suggest exchanging the lens rather than an attempt at repairs.

I have the same lens in an older version that has a slight misalignment, but mine is a small enough aberration that that I can live with it.

If you can exchange for a Tamron SP 17-50mm, f2.8 XR Di II LD IF that would be my recommendation.

richmoffitt

Thanks for the suggestion! Yeah, I figured this was pretty off. Some of my vertical shots look fine which makes me think something's actually loose.

By the way, how do you like the near focus of the Tamron? I am aware of their better QC and corner sharpness. I just might have to give them a run.

Dan7312

I'm just trying to learn something here...

What is it in this image that tells you there is a focus problem with the lens as opposed to a DOF problem or just plain OOF? The bride looks to be further away than the groom.

When I look at the grass in the picture some of the grass on the left looks in focus but none of the grass on the right hand side does. Is that the visual cue you are looking for?


TIA

ziggy53 wrote: »

It appears that the lens is misaligned and there is a strong shift in focus left to right. If you just purchased the lens and if you purchased from a reputable source I would suggest exchanging the lens rather than an attempt at repairs.

I have the same lens in an older version that has a slight misalignment, but mine is a small enough aberration that that I can live with it.

If you can exchange for a Tamron SP 17-50mm, f2.8 XR Di II LD IF that would be my recommendation.

richmoffitt

Yup. I've actually had this lens for a little while and I didn't notice the problem at first, but every once in a while I'd be like, "did I do that bad a job at focusing or pick a bad aperture?" The right side of the frame is always out of focus to some degree. You can tell it's not just a DoF issue because everything on the right side is blurry, from the trees in the background to the grass in front of the bride's feet. On the left side of the frame, objects that are the same distance away are in focus. The shot I posted here was taken at f3.5 (probably the wrong aperture for this photo, but oh well).

At least I'm glad this is explainable. It would be nicer if I didn't get a bad version of the lens. Oh well.

Freezframe

Look at the DOF!

Dan7312 wrote: »

I'm just trying to learn something here...

What is it in this image that tells you there is a focus problem with the lens as opposed to a DOF problem or just plain OOF? The bride looks to be further away than the groom.

When I look at the grass in the picture some of the grass on the left looks in focus but none of the grass on the right hand side does. Is that the visual cue you are looking for?


TIA

Dan look at the DOF to the right of the tree as oppose to the left. The trees in the background left show detail - to the right they are OOF.

Brady