CPL Filter

Haggis

While using a Jacobs 62mm Cpl polarizing filter on a Sigma 18-250mm f/3.5-6.3 DC MACRO OS HSM, I noticed that my images are blurry, but when I take it off the images are sharp.
I tried a cheap Chinese CPL and it works well. Any ideas? Anyone else having trouble with filters?

bruto

It sounds as if the filter in question is defective. That you get sharp images with another CPL makes it pretty clear the fault is not yours. One possibility is that it's not actually a circular polarizer but a linear one; those will mess up autofocus systems. Check to see if you can get a sharp image with manual focusing.

If you still can't focus, it could just be a defective piece of glass. If you can focus manually but not AF, but it's labeled as circular, then it's not a whole lot better, since either way it's not what it should be. Either way, if you can send it back or get a replacement on warranty, I would.

Haggis

Thanks for the reply. It is a CPL, not a linear, looks clear optically no distortion to see with the eye. I tried manual focus, switching off the VR, and even changed the white balance. Several test shots later, having repeated the tests with a cheap Chinese CPL and no filter at all. Was on a tripod too.
The Jacobs are terrible like camera shake, Chinese filter is very good although no filter is the best. Not a lot in it. Have contacted seller and asked for a refund. I am baffled, but not alone, as on the net under "blurry Cpl filter", there are other examples.