Canon Lens distorting horribly

W

walnutcrunch

Well-known member
This was shot without the extender on the Canon 17x7.6 CAC.
It's like there is a focus spotlight in the center and it blurs out in a circular pattern from there. It's the first time I've noticed it but it seems to be everywhere now that I'm looking. Anyone else noticed this? Is it barrel distortion and the symptom of a cheap lens?

Yikes...


 
Hrmm... Not even my Canon SD lenses do that - and they were only $125 bucks. Do you have access to another B4 mount lens to test on the camera? Are you sure your lens CAC settings are correct in the camera?
 
Okay that is encouraging. I was fearful that people were going to say that's what you get for the CAC cheapo (relatively) lenses. These responses mean maybe we have a chance of getting it fixed

I'm not sure how CAC settings could do that, but I'm all for hauling it in for a Canon evaluation.

The sad part of it is, that if it is a lens problem, I'm sitting on 400 gigs of footage shot at a remote and spectacular location that all has that same problem.
 
It's not backfocus. At least I don't think backfocus would do that. It was checked a few times because we have a habit of bumping it off its mark somehow.

In any case it's almost like a vignette effect but instead of vignette it's defocus. The backfocus problems I've seen are when zooming out from a focus, everything blurs instead of being sharp.
 
Try and disable the cac function. It would be interesting if the problem disappears. But I think it is a problem with the glasses of your lens.
 
That is not a CAC function, there is something just flat out wrong with that lens, call Canon and have them take a look at it.

Best,

jan
 
Jan_Crittenden said:
That is not a CAC function, there is something just flat out wrong with that lens, call Canon and have them take a look at it.

Best,

jan
Click to expand...

Ive put backfocus off, dodgy filters on, deliberately set CAC incorrect etc, all to see what these things look like and that lens has issues... so ditto Jans comment.

EDIT - Not too mention Ive always thought the Canon CAC lenses give a high quality image (not a fan of some other factors that are irrelevant).
 
walnutcrunch said:
These responses mean maybe we have a chance of getting it fixed
Click to expand...

I would try to get it replaced!

Does the OOF area change or move as you zoom in or out?

To me, this looks like the blades of the lens are not in correct alignment or they are defective. That is why the sides are OOF (as they move to provide zoom) and the center is more in focus, imho, and if my knowledge of lens construction is correct.

Sorry to hear about your location shoot being ruined.
 
Nobody knows why this is happening. Tried with a better lens...same problem. Tried a test camera, less of a problem but still there.

Strangely, by resetting everything in the camera back to default, it seemed to remove some of the problems.
 
Yep. The dealer brought one of their 500's in. Wasn't the best test though. As always, they were in a hurry so we couldn't be as thorough as we wanted. It takes more than 45 minutes to fully test two cameras and two lenses.

But, we were able to get the effect, but to a lesser degree, with their camera.
 
You must log in or register to reply here.
Back
Top