[SGOMMO7]

Hi, wondering if anyone can help me out here, with identifying what type of marks these are on my filter, and what would be the best options for attempting to remove them.

I’ve tried removing the marks by rubbing a microfiber cloth wetted by distilled water, but these marks show no sign of being affected by this, when the marks get wetted, they look like they go away, but as soon as the water dries the marks are back and as noticeable as ever.

The filter is a 58mm Kolari Vision Hot Mirror filter. This is the old version of Kolari Vision’s hot mirror filter, meaning this is uncoated glass! This does mean that I don’t have to worry about damaging any antireflective coating when attempting to remove the marks.

For anyone that doesn’t know a hot mirror filter is used in order to change a infrared/full-spectrum camera into a, “normal camera” that only picks up visible light, I have a infrared camera, and in order to take non-infrared photos, (a.k.a. normal photos) I have been using this hot mirror filter.

I live in a dry, low humidity environment so I don’t think it’s should be mold, as I’ve never had mold before on any filter or lens out here where I live.

I do know that some hot mirror filters are made out of types of glass that can somehow degrade, I’m not sure if these marks are symptoms of this or not, I believe it is made out of a nonstandard glass, but I didn’t think this was a lens filter that needed to be carefully sealed to avoid breakdown like some of the more exotic hot mirror filters on the market.

Any idea what these marks are or how best to attempt to remove them?

Thanks for any help.

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[Alex645]

Just a guess, but I'd think it's either delamination of the filter or some acid or chem that's reacting to the laminated surface. Don't think there is a fix.

[stevebrot]

What does Kolari say?


Steve

[SGOMMO7]

What does Kolari say?

Haven't contacted them yet. I think I might send them out an email, so they can see the photograph

[pcrichmond]

Interesting. I also own a few of the Kolari hotmirrors and haven't seen any issues with them so far.
I believe they are the Schott BG40. I also own a Schott S8612 which is noted for environmental degradation but thought the BG 38, 39 and 40 weren't as susceptible.
Will be curious to see what Kolari mentions might be the cause.

[SGOMMO7]

Okay I have contacted Kolari Vision, I gave an email with the photograph, with the same details that I posted here, I'll let you know what their responses is when I hear back from them.

[Silent Street]

Fungal growth (?)

[ramseybuckeye]

I've never heard of a hot mirror filter, so thanks for a little education. To me it looks like an imperfection in the lamination of the filter that may have just deteriorated enough to show. Otherwise I would think tiny chips, but that would be very strange and you would feel them.

Good luck on your inquiry, hopefully they will replace it.

[SGOMMO7]

Kolari Vision has contacted me back, they believe it’s oxidization of the filter. They have offered to replace the filter for me, as this filter is covered by a lifetime warranty.

Apparently there’s no way to really fix it, in fact Kolari Vision, said even trying to wash it off with water might just make it worse. Kolari Vision has updated this filter to have an AR, (antireflective) coating on it, that should protect the new updated filters from this type of oxidization.

[clickclick]

I had never heard of these and had to go read a little. Very interesting, and looks like they work well.

[SSGGeezer]

Nice that they are doing the right thing and offering a replacement rather than hemming and hawing. How much does a hot filter of 58mm go for nowadays? Are they pretty pricey as I would suspect?

[pcrichmond]

Interesting that it is oxidation and glad they are taking care of it with you. Oxidation is the fear I have with my S8612 and take special care of it to make it last as long as I can.
I'll have to keep an eye on my Kolari hot mirrors too, as they are all pre AR coating also.

[SGOMMO7]

Nice that they are doing the right thing and offering a replacement rather than hemming and hawing. How much does a hot filter of 58mm go for nowadays? Are they pretty pricey as I would suspect?

Yeah, I think they're pretty pricey, 58mm is about $70, from Kolari, which seems to be pretty close to the current pricing standard for other reputable hot mirror filters, (of course I always wonder if there's some $8 cheapo filter from China that will get me just as good of a result)

[TomB_tx]

This looks like the same degradation that hit the original sensors in the Leica M9, which they termed "corrosion" of the filter glass covering the sensor. That's the same as oxidation that Kolari suggested.
Even though my M9 was seven years old, long out of warranty, and barely showed signs of the problem, Leica replaced the sensor (and circuit board), did a full service, and returned the camera in like new condition - for free.

[WorksAsIntended]

Great customer service.