70-200 f/2.8LIS + Circ. Polarizer

Hello all,

For our trip to Jamaica, I had rented a CPL to use with a Tokina 11-16 f/2.8 I rented and thought I'd also try it out with my 70-200 f/2.8L IS that I bought used a couple months back.

I've previously been suspicious of my 70-200 because it seems like the IQ just isn't there at 200mm. However, once I attached the CPL, IQ went to hell in a hand basket. The photos looked completely out of focus. This did not happen with the Tokina.

I'd post photos, but I deleted them as I was taking them and I've already sent back the CPL.

Any thoughts on what's going on? Should I send the 70-200 in to Canon for service?

Thanks in advance!

can't recommend anything without picts.... but you deleted the evidence.

Yeah but take my word for it.. .they were very effed up at 200mm when the filter was on it.. but the same filter used on a different lens was OK.

I'll also need to take some sample shots at 200mm w/o any sort of filter to get opinions on sharpness. I don't think it's as sharp as it should be, compared to other copies I had rented in the past.

Sounds like they rented you a linear polarizer. Tokina probably looked fine because of the large depth of field that goes along with wide angle. Focus isn't as critical.

Hardcore wrote in post #10269560
Sounds like they rented you a linear polarizer. Tokina probably looked fine because of the large depth of field that goes along with wide angle. Focus isn't as critical.

I've never used a linear polarizer before... does it have the rotating front, too? This one had the rotating element to adjust effectiveness.

Granted the 70-200 2.8 is not a stellar performer at 200mm, a quality circular polarizer should not degrade images. I would suspect the filter before the lens.

Was this some $20 eBay polarizer? A quality one like a B+W won't degrade your image.

I confirmed with the site that it was not a linear polarizer - they don't stock them. Their theory:

it makes some sense that it would act differently at the long end of a zoom than the short: the phase contrast detection that the autofocus sensors use could be modified somewhat by a CP filter, especially if you were using points other than the center point only for autofocus. I haven't seen what you're describing happen, but in theory I could understand it being so under certain conditions.


Their site says they stock "mid-grade" Tiffen & Hoya filters.


Thanks for all the feedback & comments.