Today I received parcel with ZWB1, ZWB2, ZWB3 and QB21 glass from Haian Optical Glass Factory: I had plan to replace glass on unused cheap UV/CFL filters with new UV-pass glass: Closer look at disassembled filter frame: New ZWB1 37mm filter assembled: Unfortunately, new glass is 2mm thick, old glass was 1mm thick, filter frame is slim sized. I can't stack both ZWB1+QB21 to take any UV-only photo yet. QB21 is required to cut IR leaks from ZWB1, ZWB2, ZWB3 spectrum. Stay tuned.
What filter size are you looking for, 37mm? My local camera store has gobs of old filter. Maybe..............?
I know Formatt Hitech make filter rings with extra thickness to support thick glass however I'm unsure if they sell them without glass inside them, I'm also unsure about smaller sizes as I only really use the larger ones. They're also kind of expensive. The thicker 62mm filter ring can pretty easily take up to 7mm of glass for example, I'm unsure if they would even make rings of the same type in smaller sizes as they would probably cause heavy vignetting at this sort of thickness... I actually use them as part of sort of hot mirror stack rather than UV pass, heavy UV and IR on lenses which are not corrected for it such can be very ugly.
I ordered glass to use it on modern m4/3 lenses 37mm, 46mm, and just in case 55mm. I have old 49mm UV filter with 7mm frame and 3mm thread, 10mm total. New 4mm+1.5mm frames are too slim. One more idea is to use glue.
I tried this - need to place shim between rings to secure glass. Keeping this as backup solution, need 2x more unused filter frames for that.
Srb griturn sell empty frames for 2mm glass and says possibly 3mm. Link is for 37mm size but they do lots of sizes. UK based. http://srb-photographic.co.uk/37mm-empty-filter-holder-6963-p.asp
Second try with suitable old soviet 46mm filters with 2.1mm thick glass: Before conversion Blue filter disassembled. Soviet blue filter looks same like QB21 in visible spectrum only. There was lot of invisible IR leaks. Yellow-Green filter disassembled Conversion result with conversion tool on background. Now waiting for sunny days
Did some tests with mZD 45/1.8 lens and filters. There is very high IR leak, need to completely wipe red channel to see UV. qb21+zwb1 qb21+zwb1, red-200 qb21 qb21+zwb1 qb21+zwb1, red-200 qb21 qb21+zwb1 qb21+zwb1, red-200 qb21
I've briefly tried UV imaging too, with as yet no success. From what I've red on-line Copper sulfate solution is very good at blocking the NIR that leaks through U330/U340... filters. Above ~800mn IR is captured by all three visual channels on my full spectrum converted camera just ditching the red channel won't prevent IR contamination. I eventually managed to track down some UV transmitting acrylic to make my own CuSO4 filter (I have access to high purity water & CuSO4 via work). Sometime I'll get round to putting it together - even then I'll have to be very selective of which lens I use all my native lenses block UV very effectively!
I going to test new filters on industar-50 lens, it had reasonable good results on unknown small frame less 20mm filters I had. Need 35.5mm step-up ring and sunny weather.
