Rings on filters - ?

[lamefrog]

I have 4 out of about 8 B+W filters that have "developed" rings on the glass, dead center (see photo). B+W filters only. Three of the filters are 39mm (orange, yellow and ND3) and one is 46mm (yellow). The ring on the 46mm is larger. All the 39mm rings are of identical diameter. The ring on the 39mm ND3 is a half ring, as if pressure hadn't been applied evenly. The fact that these are dead center and of varying size based on filter size may indicate some kind of physical effect. Also I think I first noticed this occurrence on one of the filters after a flight. The filter had been in a suitcase in the cargo hold. But not sure about this. Could this be a manufacturing defect? Any ideas on why, how this happened?

 

[charjohncarter]

No idea, but 'Yikes' have a few B+W filters. I'll have to check them.

 

[wwfloyd]

Did you check the storage cases (I'm unfamiliar, for BW), to see if there are circular rises in the liner?

 

[randy stewart]

Just an idea not based on personal experience, but it may be some sort of delamination or flaw in the coating. If it were one of the old Kodak Watten filters made by laminating a gel filter between glass plates, delamination would be near certain.

 

[Rayt]

That’s weird. I have about 50 B+W filters for b/w photography from 37mm to 105mm some very old and none has this ring.

 

[shimokita]

the only thing I can think of is storage method, change in temperature, and/or change in air pressure. I have often stored filters in the cargo hold with no noticable effect... for me max seven hour flights, mostly summer months...

I have seen auto windscreen laminate "bubble" due to intense heat