Contapol B50 filter delamination spots

[Barry Martin]

Are these blemishes affecting the centre of a Contapol polarising filter—pictured below—cause for concern? This filter was recently purchased online and the seller, remarkably, managed to overlook mentioning these delamination (?) spots.

Specifically, do they have much influence on the item's value, and are they likely to affect image quality?

These filters appear to be difficult to come by which spoils my appetite for returning it for a refund. The price paid was about 70 GBP (90 USD) whereas one in mint condition, and the only one I can find online for sale, has an asking price of this amount. I'd appreciate some guidance.

 

[AgX]

At these spots the filter will act as if there was an additional glass pane. That's all. In the worst case the delamination patches would not have parallel surfaces, thus acting as tiny lenses. In theory. It would still not be visible.

However these spots could be seen as indication of future delamination.

 

[anfenglin]

Well, sometimes, these things are in storage so long that they may start to develop issues. Especially things which are hard to sell are prone for this to happen.
I work in an online store and we check at least the lenses if they have been in our shop and our storage for a long time.
Since we sell used gear, the rate for things to develop faults is much higher as for new gear.
Checking each and every filter is nigh on impossible because they often are in packaging and an additional baggy.
I've seen this delamination in lots of old filters, especially in old pol filters.
Never shot with one that had these spots, never even shot with a good one.

 

[Anon Ymous]

Is that a Zeiss branded petri dish?

 

[fstop]

Throw it out and buy another one.

 

[Fixcinater]

They likely have more influence on the value than on actual performance. If you use a hood with the filter, it would further reduce the effect the bubbles may have on it.

You may be able to replace the glass if it is not swaged in place, if you are interested in using the "correct" housing. This may increase performance over the older coatings in the glass, if you use a modern multi-coated polarizer glass.