What's going on with my 47B? Is this fungus?

[bluestar01]

Apologies for the poor angles, can provide more if needed! I recently whipped out my trichrome filters again after not shooting with them for a while, and noticed this spot on my 47B. At first it looked like a plastic sticker on the filter was peeling or had a bubble in it, then I noticed the pattern. It's sandwiched between glass I think, but it's more toward the back face, as it's much darker/harder to see when looking at the filter front-on. This view is through the back.

Is it fungus? Any remedies on how to get rid of it / fix this? Or is this filter gonna have to retire....

 

[Freakscene]

It’s delamination or ‘separation’. A lot of filters are not a single piece of glass, but are different layers glued or laminated together. What has happened here is that the layers are coming apart.

At the edge of the filter and given that you will be sandwiching the exposures with the R and G filter exposures I doubt it will have much impact.

 

[Retro-Grouch]

Completely agree with Freakscene. I've seen this happen often with Tiffen filters, which are constructed the same way. They advertise their lamination process as an asset, claiming it provides more consistency. I emphatically disagree, and won't use Tiffen filters because of the delamination problem, their propensity for the inner resin to fog, and the added thickness. You don't mention the brand of your filter, but I'll bet it's a Tiffen.
There's no way to repair this, but I also agree that you'll see little or no impact. Keep an eye on the problem, though, as the defect can spread. Beyond that, I'm not sure of the cause. Impact? Moisture? The Universe deciding to give you a bad day?

 

[Freakscene]

Completely agree with Freakscene. I've seen this happen often with Tiffen filters, which are constructed the same way. They advertise their lamination process as an asset, claiming it provides more consistency. I emphatically disagree, and won't use Tiffen filters because of the delamination problem, their propensity for the inner resin to fog, and the added thickness. You don't mention the brand of your filter, but I'll bet it's a Tiffen.
There's no way to repair this, but I also agree that you'll see little or no impact. Keep an eye on the problem, though, as the defect can spread. Beyond that, I'm not sure of the cause. Impact? Moisture? The Universe deciding to give you a bad day?

Rapid temperature change is a very likely cause too, like going into a heated building from a very cold day or going into airconditioning from an extremely hot day.

 

[bluestar01]

It’s delamination or ‘separation’. A lot of filters are not a single piece of glass, but are different layers glued or laminated together. What has happened here is that the layers are coming apart.

At the edge of the filter and given that you will be sandwiching the exposures with the R and G filter exposures I doubt it will have much impact.

Completely agree with Freakscene. I've seen this happen often with Tiffen filters, which are constructed the same way. They advertise their lamination process as an asset, claiming it provides more consistency. I emphatically disagree, and won't use Tiffen filters because of the delamination problem, their propensity for the inner resin to fog, and the added thickness. You don't mention the brand of your filter, but I'll bet it's a Tiffen.
There's no way to repair this, but I also agree that you'll see little or no impact. Keep an eye on the problem, though, as the defect can spread. Beyond that, I'm not sure of the cause. Impact? Moisture? The Universe deciding to give you a bad day?

Appreciate the responses! It's lookin' like you guys are probably right..! As I say, my initial reaction was that it looked like a protective plastic film was peeling from the filter, like the kind you get on new electronics, or a phone screen protector that bubbles on the edges as it starts to come off. So this makes sense!

Haha I had posted this elsewhere and included the brand of filter in the title and just noticed I missed it out here, but you're absolutely right, it is indeed a Tiffen 47B! My Green 58 is also a Tiffen (and I have Black Pro Mists), here's hoping they don't follow the same fate...
When I was looking at RGB filters, Tiffen seem to be the only easily available blue and green filters that I could find!

But yeah, I guessed that it would be a case of there's not much that I can do here. As you say, I mostly use 40mm or 50mm so, the edge of the filter should be out of the FOV. Fingers crossed it doesn't spread much..! And as for the cause, I last used them ~June, and this is the UK so we have zero air conditioning! Sudden temperature changes shouldn't have been a problem, and they're stored on the same set of shelves as my vinyl records, so they're definitely not stored poorly! My other filters seem fine so, perhaps it was just the Universe decided to take its anger out on my poor 47B that one day...!