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UltravioletPhotography

Kg2 filter source?


Namestom

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You can guess, but if you want to know, then get an IRchrome, un-glue it with solvent, test each glass with a spectrometer,

find the glass to match (like you say, both layers are 1mm each), then have them AR coated (or skip that if you want for tests), glue them together (or skip that for tests, and just make separate filters for stacking),

but be prepared for the light at the end of the tunnel to be orange, not red.

I mean if you like orange, then there are a LOT of ways to get the same results. Easiest being B-410 2mm + KG3 2mm, or a bunch of Lee filters + KG3 2mm, and a few dichroic filters... the list is long.

If you want red though, with SOOC, then the list narrows down to Lee 729 + KG3.

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As Steve's graph above show the KG2, 1mm has a Ti of ca 60% at 850nm.

2mm thickness KG2 will be closer to 35% at 850nm

If you want a lower transmission some other glass type and thicknesses can be interesting.

 

You must have quite some luck to find something fitting all your parameters, glas-material thickness and diameter.

 

To get exactly that, I think that, the best alternative is a careful nagging and friendly persuasion of Steve.

Eventually you might have him make the filter for you.

Especially if you can motivate the need for that material type and thickness, making it likely that he also can sell the remains of the material he must grind to thickness, making your filter.

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Ulf makes it sound so easy... :wink: Well not really, but he makes a good point about need.

The real issue is the need.

2mm is much easier because there are so many 2mm thick filters that can be grouped together.

There are some 1.5mm and 1mm filters, but they need to be grouped into glass type hardness, so it gets complicated.

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Steve - I know that it is not easy, especially with producing high quality filters custom made in small numbers like you do.

I just wanted to leave the explaining of the difficulties of the manufacturing-process to you, if ever the demand for an odd custom dimensions filter arrises.

 

I am confident that if someone was prepared to pay for all the material wasted and extra job, to produce one single filter, wasting several sheets of material you would do it.

Then the final price for that filter would be quite high above the normal prices.

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This is entirely theory, and if you ask me a theory about how to make orange.

Why don't I get too thrilled about the IRchrome? Because I have one, and it has orange foliage SOOC. Ask Birna, I got it from her.

Orange may be what is wanted by some, but there are other ways of doing the same.

It is unknown what the two glass types are in that stack. A spectrometer would help.

So making KG2 1mm for that reason alone, on a hunch... how much glass would I have left over, who would want it?

Like I said, get one, scan it, figure out what is used... but why reverse engineer that filter when there are so many other stacks with known equations.

Of course, if you get one, then you will not have to, or probably still want to reverse engineer it.

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