What's in the name: filter puzzles

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

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ModelZ
Posts: 71
Joined: Sun Nov 01, 2020 4:34 am
Location: Northern Europe

What's in the name: filter puzzles

Post by ModelZ »

Been lately tinkering with two fluorescence scopes. One DIY and one old school - no ready made cubes here. So you have to figure out how the filters & dichros match up. Its been both fascinating and frustrating.

Part of the problem are the cryptic filter codes. If I have a mystery filter at hand I can try to measure it against my existing short and long pass filters to figure it out what it's about. If I just have a code then what? Well, BP, LP, SP, KP, TK... embedded in somewhere there is a clear hint. Even rudimentary German helps to guess. Found also short code guides in Nikon and Olympus pages. Schott pages are useful and e.g. ultravioletphotography.com has a handy cross ref. for some manufacturer's most common filters.

So my question is this: is there in some dark corner of the net a "filter bible" that some tormented soul who has been fighting these same ghosts has compiled?

Just to hint at these strange flavors... Olympus has Y-filters (yellow long pass) but then there is also e.g. EY455. Dug up some Oly brochures and finally Abramowitz's fluoro book to no avail. E=excitation only, optical quality ok for that but not for the image light train? Or perhaps just Extra? Add on to sharpen the excitation distribution. Oly infos I found are insufficient.

Anyone ever encountered CAT425? Reichert offered it for violet excitation. I suspect it is (interference?) BP filter of some bandwidth at the given peak wavelength. But again, just a guess.

It's not just that manufacturers insist on their own notations, it'd even more dense. Schott is German and Very Logical but what the heck is the thinking behind e.g. the code BG36? Its transmission curve is like a seismograph plot at earthquake while its nearest neighbors on both sided (BG25, BG38, 39 etc.) all have smooth unimodal curves and are mutual relatives (red suppression/IR-block etc.).

Well, this got longish. I go now back to my hole and quietly stare at my little disks...

Cryptically yours, Karl

Pau
Site Admin
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Location: Valencia, Spain

Re: What's in the name: filter puzzles

Post by Pau »

Interesting post, this is a somewhat complex world, often unnecessarily arcane.
So my question is this: is there in some dark corner of the net a "filter bible" that some tormented soul who has been fighting these same ghosts has compiled?
I appreciate the sense of humor.
I don't think that anyone here has access to that hidden "filter bible" but be sure that there are highly skilled members able to answer specific questions on filters.
Pau

ModelZ
Posts: 71
Joined: Sun Nov 01, 2020 4:34 am
Location: Northern Europe

Re: What's in the name: filter puzzles

Post by ModelZ »

Been rather quiet in this channel... the olympians, zeissians etc. seem to prefer to keep their fluoro emissions low ;-)

But thanks Pau for chiming in. Also appreciate your past fine articles of fluoro LED conversion - served as inspiration and more when I built my first epi fluoro head (from OI-17 up).

Cheers, -Karl

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Re: What's in the name: filter puzzles

Post by Ichthyophthirius »

Hi,

I suspect the Schott glass names are chronological. They have a 150+ year history, it would be logical to stick to 1 name = 1 glass rather than constantly renaming them according to their property lineup.

Apart from that, Schott:
UG: Black and blue glasses, UV transmitting
BG: Blue, blue-green, and multi-band glasses
VG Green glass
GG: Nearly colorless to yellow glasses, IR transmitting
OG: Orange glasses, IR transmitting
RG:Red and black glasses, IR transmitting
NG:Neutral density glasses with uniform attenuation in the visible
range
N-WG: Colorless glasses with different cutoffs in the UV,
transmitting in the visible range and the IR
KG: Virtually colorless glasses with high transmission in the visible
and effective absorption in the IR (heat protection filters)

Fluorescence microscopy is an application for which a number of different materials were used; coloured glasses, gelatin filters, interference filters and more. Some of the confusion might stem from the fact that all of these materials have their own naming conventions.

Luckily, since the Ploemopak they often come as units of two preinstalled filters + beamsplitter (cubes) and the label should usually refer to the properties in the manufacturer's manuals. Leitz, for example, had single letters that referred to the application/property (like H3: H = violet and blue excitation, green emission; 3 = third product generation) https://www.ronaldschulte.nl/files/filt ... eszenz.pdf

But I agree; when the manufacturer manuals become unavailable it's hard to track down the specifics. I had the same problem with a Chroma filter https://www.chroma.com/sites/default/fi ... ilters.pdf a while back. On the other hand, don't the interference filters age quite rapidly? By the time the manuals become out-of-date the filters should be at the end of their lifetme as well. 8-[

ModelZ
Posts: 71
Joined: Sun Nov 01, 2020 4:34 am
Location: Northern Europe

Re: What's in the name: filter puzzles

Post by ModelZ »

Excellent summary and links, thanks Ichthyophthirius. Historical baggage & a case of profound nonstandardization here all over as you note.
Omega thing will be a good, long read. I've ordered some some stuff from them. Dr. Johnson has an ebay outlet, running at least part of time, but there I never came across the Catalog file. Perhaps I was blind or they just thought it was a bit old and didn't want to promote. Btw some of his filters likely have just arrived to Mars in Perseverance optics!
R. Schulte's site is nice. Among other things it also has Leitz's more introductory piece with some curve infos, www.ronaldschulte.nl/en/files/Leitz-Fluorescence.pdf
The aging point well taken. I wonder how easily you can actually see it as degradation of the deposited layers? Burned old filters seem a piece of cake to recognize. I don't hunt old filters per se, but their manufacturer codes come up when you investigate these set-ups. Since I don't order packaged sets i.e. cubes I'd like to check manufacturer's recommendations for filter sets and then start off with something similar preferably using more modern filters. But to do that one first have to understand what they are talking about!
Oh well, a fascinating field. And I haven't even touched fluorochromes yet...
Cheers, -Karl

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