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I know there are mixed opinions on Chinese filters here on the forum. I myself have had a less than ideal experience in the past when one of the first ones I got had visible striations on its surface, and the question of whether the filter would actually match the transmission spectra provided for them has always been an issue. I wanted to provide some positive news though, regarding a recent purchase, and perhaps lay some fears to rest regarding these things. For one of my client projects I found myself in need of large filters (at least 190mm diameter) to fit in front of studio flashes, to remove most of the visible and IR light from the flashes while letting as much UV from 300-370nm though. I did not need to block all the visible and IR, just prevent enough of it from reaching the subject so my bandpass UV filters on the lens could do their job, without needing to filter out huge amounts of out of band light. The size was the big issue here, given that normally we are used to thinking of filters in the 52mm diameter region. While I looked at custom ones from the normal suppliers, cost would have been prohibitive. I found myself looking at ZWB1 which is often advertised as being a UG11 equivalent. In 3mm thickness, based on what I had seen for it, it should have good UV transmission, while blocking pretty much all of the visible up to about 680nm. It would then let some IR through from 680nm to about 800nm, but it would block 90% of the IR in that region. In theory, good enough for my needs. The supplier I approached was Tangsinuo, who a few people on here have used - http://www.tangsinuo.com/productgrouplist-804193211/UV_Pass_Filters.html After a few emails about the logistics of having filters made, and including them sending me through some actual transmission data for the pieces I was interested in, I ended up placing quite a big order - 2x 200x200mm ZWB1 3mm thick, 2x 200x200mm ZWB3 3mm thick, ZWB1 2mm thick 77mm diameter, ZWB3 2mm thick 77mm diameter, ZWB3 2 and 3mm thick 52mm diameter, and even 20x 1mm thick 75x25mm JGS1 fused silica slides for my microscope. Cost including expedited shipping from China to the UK was a surprise. While I wont say the exact amount, for everything it was about the same a one and a half, 2 inch diameter Baader U filters, and the shipping was just over 10% of that cost. The package arrived yesterday - took just over a week from China to the UK. Very well packaged, very secure. Got everything out and tested it, and I must say, I'm impressed. No visible striations on the glass, nice finish, chamfered edges etc. The 77mm filters were mounted in rings as was one of the 52mm one (the other is just a disc which I can mount myself as it is a bit thicker than they normally mount in 52mm filter rings). The microscope slides are individually packaged. What amazed me most though was the large filters - 200mm square and 3mm thick. You don't often see UV filters this big - below is a photo of one of the ZWB1 ones. Also, one of the 77mm filters in its ring and supplied case. Transmission spectra (measured by me) of the camera lens filters, and the 200mm x 200mm large ones are given below. Not bothered putting the fused silica microscope transmission in the graphs, as well it is a bit boring (high transmission from 250nm to 1100nm). If I'm being picky, there is a little bit of variability if you look at the two ZWB3 2mm thick filters in the above graphs - they don't completely overlap. But that is a minor gripe for me, especially given the cost. Overall, very impressed with Tangsinuo and would definitely consider using them again, probably more if I wanted big filters for lights as these are something which are hard to get from other suppliers.

I haven't bought the ZWB-1 filter yet with the black filter (maybe ZWB-2 1mm) of the Alonefire 10w 365nm flashlight I did this test. (last photo BG39 + BG 25 + black filter) the result is amazing all the flowers are black What ? P.S. A7 + Nikkor-H 50 f8~

The Baader doesn't work well front mounted on a wide angle lens. There isn't an easy way to rear mount it on my FF DSLR. So what filter stack is closest in performance? Thanks, Doug A

One of my first reflected UV shots with UV modified Pentax AF540 flash. Pentax K-1, Pentax bellows with 3 extension tubes, Nikon El-Nikkor 135 f5.6 enlarging lens. Bellows has a handy internal filter thread to allow filters to be mounted inside it. Used the Ioriginal supplied ZWB-1 2mm/ BG39 2.3mm filter stack. The flash was placed less than 2" from flower. Flash had 2 2mm filters, probably ZWB-1, borrowed from 2 NEMO torches. The extra 4mm of flash filtration is required to squelch leakage. Exposure f16 1/200 ISO2000. This flower is very small at about 10mm. Magnification is close to 2x life size. This image was slightly cropped for composition. Lens was used at f16 and would probably perform better reversed. Unfortunately, I don't have the necessary adapters to do that yet. I may wait to do this since the 135mm lens really is too long of a focal length to work comfortably on the bellows at these magnifications. Looking for an El-Nikkor 80mm for these applications. Any suggestions welcome. Thanks for looking, Doug A

Living less than 500 foot above sea level, I'm convinced electronic flash is needed. Last year I bought some Pentax AF540 FGZ shoe mount flashes. One was thrown in because it was missing the pull out white bounce card and flip down wide-angle diffusion panel. Now, with my help, it's missing the front Fresnel lens. I've had different recommendations for filtering. One said put 6mm of Chinese ZWB-1 on the flash. Another is using Hoya U340 and Midopt BP 365 camera filters. As a quick experiment, I borrowed the ZWB-1 filters out of the two Nemo torches. This gives me 4mm on the flash. With the Pentax K1 Full Spectrum, original metal body Nikon EL-Nikkor 135mm (standard ZWB-1/BG39 filter stack) on Pentax bellows, the pictures don't look bad. I'm using the same custom white balance set for Ioriginal 35mm lens. Flash looks fairly similar to daylight. Same setup on Ioriginal 35 lens has a little bit of a yellowish tint. So what filters are recommended for a UV flash? Thanks, Doug A

So I had this 590 filter stashed away, figured I'd try some IR color before winter. I had to go wide open, because trying to clean sensor with home remedies is a pain. Shot with F/S Canon 2000D/T7 24mm, K590. I really like the Blue foliage out of camera(No Man's Sky game vibe) but trying out some swapping with a blue sky.

There was a little bit of intermittent sun beams sneaking through the clouds, so I tried to catch a few for some filters tests. David Twede posted a filter test a while back (in his blog, see link). https://next-eyes.blogspot.com/2019/ He suggested the equivalent would be Lee 156 Chocolate Polyester sheet filter. The 156 is a brown filter, and although I wasn't able to find a graph for the Tiffen Sepia filters, they are the same color to the eye as the 156, and they work the same (I am using a Tiffen Sepia 2, they have 1, 2, and 3, 3 being darkest). Tiffen also has a Tobacco filter, which is also a similar color to the Sepia, but I don't have the Tobacco to try. Basically these 'brown' filters show the full visual range, blue skies, out of camera, only the foliage is changed to lavender/purple tones. Other filters will render lavender foliage SOOC with a full spectrum camera, but the sky would not be blue like it is with these, and the visual color would be more altered also. So these brown filters are interesting in that they leave most of the visual range alone, and change only the foliage to lavender/purple. Also, I tested the IR Chrome. My one word assessment is 'orange'. I get this same look using B-410 + KG3, or a number of other polyester filters, etc.. All these tests were made using individual in camera white balance for each filter using a large full frame WhiBal gray card. These shots are all straight out of camera (SOOC), no processing. I also tried white balance from RAW in Photo Ninja, and was unable to find any better white balance than the original gray card. Lee 156 is a polyester film filter, very thin, like a gel filter, but made of polyester. Tiffen Sepia is a film filter (of some kind) sandwiched between clear glass. All of the Tiffen filters are constructed this way, color comes from the film layer, not from the glass. IR Chrome is two layers of glass glued together (1mm thick each = 2mm thick total) . The Lee 156 Chocolate Polyester sheet filter was cut to fit the back of my lens, and taped in place. The Tiffen Sepia 2 filter is a 52mm filter, and it was used on the front of my lens, as was the IR Chrome. Nikon D7000 UV/IR, 18-55mm VR lens. All Aperture Priority F10. Lee 156 Chocolate transmission graph Lee 156 Chocolate (rear of lens mounted) Tiffen Sepia 2 (front mounted) IR Chrome (front mounted)

I ordered a Lee Filter swatch book. Quite cheap. In around there area of Scuba blue is two other filters with slightly different curves. The swatch book is 39mm x 89 mm, perfect for microscope slides, which I intended to play with "optical colour". Holding the Scuba 729 filter infront of my Sigma 30mm f2.8 lens on my EM1 full spectrum, I was able to get an in camera WB. I was hard now for some reason and I needed the White Color checker to get it. Not sure why my EM1 is acting up with WB settings now. Here is BW486 regular photo: Here is straight out of camera using Suba blue 729 with it for the WB setting: Scuba blue in my book as peak max at 500nm at 40% with about 30% peak at 800nm Here is a neighbor filter QFD Blue 727 using the Scuba blue WB setting: This filter has a 495nm peak max at 40% with 25% peak at 800nm Here is an other filter Medium Blue Green #116, with Scuba blue WB setting: This fitler has a peak max at 500nm at 60% with 50% peak at 800nm. I don't have a weak IR blocking filter to test. There also seems to be other filters in the area that might be interesting. So if you really want that in camera Aerochrome look on the cheap, I would recommend ordering a cheap Swatch book from Lee and find out the best filter for your camera.

Made a UV WB target by wrapping many layers of plummer's tape around a flat piece of cardboard. The full spectrum Pentax K-1 is able to set a custom WB with the Ioriginal Kyoei 35 clone and ZWB1(2mm)/BG38(2.3mm) filter set. The photos come out mostly B&W. Sometimes there are some blue tints. Dandelions do come out yellow with black bull's-eye center. Is this most the colors the lens and filter combo will produce? Also managed to get the El-Nikkor original 135mm enlarging lens on the Pentax bellows. I like the filters fitting inside the bellows. Less flare and contrast loss. Any potted plants that would help test these setup's color response? It needs to be readily available in a Midwestern US plant store. Oops, just found a 2015 sticky that lists some plants. Not sure which plant would produce the most colors in reflected UV photos. Thanks, Doug A

A tip from you who you have a lot of "eye" and experience Is arrived new bg25 and a bg18 (he didn't have the gb39 - ø75mm) I did some tests for my wet collodion search I used the A7 F.S. with various old Nikon lenses, which I don't put because the results with the same stack of filters is the same. . All RAW files developed with Capture One, All filters 2 mm thickness Eninchrom flash light with "light" tube without anti UV yellow . Then I compared the standard Nikon Z7 with the old Nikkor-H 50 F2 (born in 1967) with and without the BG25. The answer with the filter is logical, cut all IR and yellow, the Blu area has no details, does not see UV, the sunflower is all dark. The photos with A7 F.S. And the various filters have confused me. Can you help me interpret photos? The graphics of the filters is easy to understand, but the diversity of the results of color i dont understand it; Depends on the pile, the lens or sensor? . Thanks Toni

A bright sunny day usually has more UV at midday. I've been shooting during this time. Recently, a blog (not here) said to avoid this because IR is the strongest and has more chance to overload the blocking filter. Do you agree with this? Does the ratio of IR to UV change on a sunny day? Thanks, Doug A

Setup: - Nikon D600 mono. - Nikkor 50/1.8 AF-D. - Kolari UV-pass filter. *Note* the frame edges - those are Bayer CFA ramainders - photos would be that darker with CFA. All photos handheld, the aperture was usually f=2.2 but from 1.8 to 2.8. Exposure usually 1/50s, sometimes 1/30s. ISO auto from 100 to 1600 - this is what actually changed. All photos were just Live View "auto" with fixed aperture mode, usually at f=2.2, minimum shutter time 1/50s or 1/30s sometimes.

I now have a whole bunch of ZWB1 filters and thought a fun thickness test in sunlight would be ok. So the lighting isn't perfect but mostly clear sky only one had odd exposure time. All these are shot at the same white balance setting except for the first BG38 4mm image. I was using the Nikor 80mm f5.6 lens at F8. However I have my SvBony 0.5x booster lens on as well. Forgot it was there, so the edges will be blurry and the center should be sharper. This also allows for faster shutter speeds. All image with EM1mk1 full spectrum camera set to ISO 200. 4mm BG38 ISO 200 1/1000 F8: I have two of the new 8mm solid thickness filters so I tested them first 8mm A filter ZWB1 ISO 200 F8 1.6 seconds: 8mm B filter ZWB1 ISO 200 F8 1.6 seconds: 8mm A + 8mm B ZWB1 filters ISO 200 F8 5 seconds: Next I have 6 filters of Zwb1 that are 2mm thick (one is 52mm) the others are 58mm for light modifications 2mm ZWB1 (1 filter) only 1/40 seconds: 4mm ZWB1 (2 filters stacked) only 1/3 seconds: 6mm ZWB1 (3 filters stacked) only 1.3 seconds: 8mm ZWB1 (4 filters stacked) only 2 seconds: 10mm ZWB1 (5 filters stacked) only 3.2 seconds: 12mm ZWB1 (6 filters stacked) only 4 seconds: 8mmA ZWB1 stacked with 2 of the 2mm filters (total 12mm) 3.2 seconds: 8mmA ZWB1 stacked with 3 of the 2mm filters (total 14mm) 4 seconds: 8mmA ZWB1 stacked with 4 of the 2mm filters (total 16mm) 8 seconds: 8mmA ZWB1 stacked with 5 of the 2mm filters (total 18mm) 8 seconds: 8mmA ZWB1 stacked with 6 of the 2mm filters (total 20mm) 13 seconds: 8mmA ZWB1 stacked with 8mm B ZWB1 with 6 of the 2mm filters (Total 28mm) 25 seconds:

This is related to this previous topic: https://www.ultravio...__fromsearch__1 Here is a comparison of all 4 combination filter graph types from the 2017 version of the Schott Filter Program . Graph types are: Combi Diabatic T graph (T = transmittance, including calculations for surface reflection) (Combi = combination, or combined/stacked filters) Combi Diabatic Ti graph (Ti = internal transmittance, with no calculations for surface reflection) Combi Linear Ti graph Normalized Ti graph Several things to point out: 1) The 'data input' page has a default number in the Peff field at the bottom of the page. That default (which I think was about 0.91 to 0.94 in my first use of the program) is about the same as the average reflection factor (P) for most Schott filters. Since gluing a stack together only leaves two sides of reflection then the Peff would be close to the average P number for most Schott filter types. However, if you are not gluing the filters together, such as screwing several filters together as a stack, then you can calculate the Peff and enter it manually. First, find the reflectance factor P for each type of glass in the stack, which is located in the 'data table' page. Multiply all the P numbers together, for example for a two filter stack, P x P = Peff, or for a three filter stack, P x P x P = Peff, etc.. Then enter the Peff into the Peff field at the bottom of the 'data input' page. The Peff is only used by the program when drawing a Combi Diabatic T graph. It is not used for Combi Diabatic Ti, Combi Linear Ti, or Combi Normalized graphs. The Peff will be different depending on if the stack is glued or non-glued, and (in the case of non-glued) how many filters there are in the stack. 2) There is a typo in the 'data input' page header, I have pointed it out in the screen shot below. "ti COMBI = Peff ( ti1 x ti2 x ti3 x ti4 x ti5 )" should read as "Ti COMBI = Peff ( ti1 x ti2 x ti3 x ti4 x ti5 )" (I think that is just a simple cosmetic mistake in the program, which has no calculation influence) Here is a shot of the 'data table' page, showing where you get the reflection P data to calculate the Peff to enter in the 'data input' page. Here is the 'data input' page, where you can enter the Peff calculation at the bottom (as well as the glass types in the stack, thicknesses, etc.. In this UG5 + S8612 stack, the Peff = the P of each glass type multiplied together, 0.91 x 0.913. This shows all 4 graph types, including T at the top which is calculated as a non-glued stack. I am still working on lining these up cosmetically and other details such as 1E-03 vs 1E-10 graph depth. Also notice the Diabatic T and Diabatic Ti graphs have different % line spacing. Some of these details need to be fine tuned still once I figure out how to fix them

Setup: - Nikon D600 mono. - Nikkor 50/1.8 AF-D. - Kolari UV-pass filter. All photos handheld, the aperture was usually f=2.2 but from 1.8 to 2.8. Exposure usually 1/50s, sometimes 1/30s. ISO auto from 100 to 1600 - this is what actually changed. All photos were just Live View "auto" with fixed aperture mode, usually at f=2.2, minimum shutter time 1/50s or 1/30s sometimes.

I've just had a very geeky few days evaluating a Phase One IQ4 Achromatic camera. Medium format BSI sensor (53.4 mm x 40.0 mm), 151Mp, black and white. Thanks to Teamwork Digital Ltd in the UK for making this possible and sending it to me along with an adapter to use my Hasselblad lenses and a really solid tripod. This was one that really interested me, as it should be good for UV as well as visible and IR, and I could try out my Zeiss UV Sonnar on it, as that was made for the Hasselblad 6x6 cameras. First impressions, it is very solidly built, and very well made. Here's a couple of pictures of the camera with some of the lenses I was trying out (El Nikkor 80mm f5.6, and the Zeiss UV Sonnar). Was able to take some images in UV, visible and IR and thought I'd share a few here. Landscape - Chobham Common in the UK in the IR and visible. Natural light in the evening. IR (Zeiss UV Sonnar, Hoya R72) Visible (Zeiss UV Sonnar, Schott S8612 1.5mm plus 420nm long pass) IR (Zeiss UV Sonnar, Hoya R72) Product shot in visible light using a big softbox. Single Bowens GM500 flash. Flower shots (from local flower shop - Tangerine and Green, Englefield Green, UK), in visible and UV. Single Bowens GM500 flash with quartz tube. Sunflower in UV (El Nikkor 80mm f5.6, Baader U) Not sure on this one - Dahlia perhaps - anyway, a white flower in UV and visible. Visible (Schott S8612 1.5mm plus 420nm long pass) UV (Baader U) These images have obviously all been reduced in resolution for sharing. As an example of the resolution of the original images, below is the image of the Sunflower in the UV along with a region marked in red. That little red square is 1000 pixels by 1000 pixels, and this is what it looks like in the original image. Working with the files is certainly challenging for the computer - a full size image in high quality jpeg is around 60Mb and the raw files are pushing 200Mb. You need a lot of storage with a camera like this. Not seen much UV imaging done with medium format, so thought it would be interesting to share. Unfortunately with only 3 days with it, I barely even learned how to use it, but it certainly impressed me in that short time. It has now sadly gone back to the dealer, and if I want to buy one I'll need to get buying those lottery tickets.....

I was recently sent an old Kodak Wratten 18a filter by a friend. It's un-threaded and is described as 'size 370'. Here's what it looks like. It's very thick - about 4.5mm, and almost as thick as the ring it is mounted in. Not sure if this thickness was normal for 18a, as I've not seen an old one before. Here's the transmission spectra of it. Sharing it here as I think it is an interesting historic item.

A little bit of fun today. For a talk I'm writing I needed some photos of a subject in UVA and B captured in daylight, to be able to compare those with a different light source - mercury xenon lamp. My usual model (my wife) is currently away, so I called upon the services of one of her little stuffed toys to fill that role. Here's the toy in daylight, sat next to a Labsphere 20% diffuse reflectance standard. Taken just using the camera phone. UV imaging was done with a monochrome converted Nikon d850 and Rayfact 105mm UV lens (f8 and ISO800). Filter for UVA was 365nm Edmund Optics 10nm bandpass filter combined with a Hoya U-340 4mm. Filter for UVB was a 313nm Edmund Optics 10nm bandpass filter, again combined with the Hoya U-340 4mm. UVA image (365nm, 1/4s exposure, f8 ISO800) UVB image (313nm, 4s exposure, f8 ISO800) I checked for leaks in UVB image by using a Hoya R72 in combination with the filters and got a completely black image. I was actually really surprised by how different the UVA and B images looked - must be the dyes in the wool. Looking at the RAW files the UVB image is about a third of a stop darker than the UVA one, but it was close enough for what I need it for. UVB imaging in daylight is a huge challenge, even with a monochrome converted camera and 'non-glass' UV lens. The Edmund Optics filter alone, despite being OD4, was not up to the job of filtering unwanted wavelengths. Using it in combination with a Hoya U-340 4mm did the trick though.

A few years ago I ran an unfair test on the ZWB1 for visible light leaks. In the test I compared the ZWB1 to the wrong UV-pass filters. I have since retired that topic. The equivalent filters to ZWB1 are Hoya U-340 and Schott UG11. These should be used in any comparative tests of the ZWB1. Anyway, today I was cleaning filters and decided to look at visible light leaks in my Hoya U-340 x 1.0 mm and ZWB1 x 1.5 mm by making some long exposures. Each dual bandpass filter was stacked with a Baader UV/IR-Cut filter to cut UV and with an S8612 x 2.0 mm to cut IR. I focused on a brightly colored bunch of Coreopsis flowers and ran 5", 10", 15" and 30" exposures. They are attached below. For both filters, a lot of visible light was captured. That is not unexpected given the thinness of the two filters. When this kind of glass is used as a substrate for either a dichroic or an absorptive UV-pass filter, the manufacturer would ensure that this visible light leak would be blocked along with all the passed IR. However, we cannot so easily block visible light leaks in our Do-It-Yourself UV-pass filter stacks. We've had some discussion on the forum about the validity of such forcing tests. I can support the view that we should only check for visible light leaks in our UV-pass filtration by using normal exposure times. But I wanted to make a forcing test anyway to ensure I captured a lot of the visible leak so that I could look at in Raw Digger. Nikon D610-full-spectrum + UV-Nikkor 105/4.5 + Sunlight (lots of it) All photos f/8 @ ISO-400. All photos as shot, no edits. Resized and labeled in Photo Mechanic. The Nikon was set to a custom visible white balance. It was windy!! U-340 x 1.0 mm + S8612 x 2.0 mm + Baader UV/IR-Cut 5 seconds 10 seconds 15 seconds ZWB1 x 1.5 mm + S8612 x 2.0 mm + Baader UV/IR-Cut 5 seconds 10 seconds 15 seconds Here are 30" second exposures for making Raw Composites. U-340 stack as above for 30" It's like we almost have an actual visible photo here from all this leaked visible light. But the colors are a bit "off". The coreopsis is yellow with a dark red center. So there isn't enough yellow here. U-340 stack for 30" Raw Composite, No white balance, no color profiles. But I suppose I thought there was going to be more green leak? ZWB1 stack as above for 30" Same remarks about color....not enough yellow. ZWB1 stack for 30" Raw Composite Again, not as green as expected. Conclusion: I don't have anything from this that we didn't already know except that I had thought the visible light which would get through would have more green. Mostly I just wanted to see what happened when I tried these long exposure stacks.

A couple of filters arrived today from Russia. They are 3mm and 5mm thick microscope filters (32mm diameter). I got them from ebay and they were 13USD for the 2 filters and 9USD for the shipping, so for that it was worth a gamble. The filters; Here's the transmission spectra for them, full scale, and focusing on the 0-1% transmission range to see whether there is any visible light getting through. Looks like they could be useful filters. If anyone knows any more about these, please feel free to comment as I don't know anything about them (the ebay advert called them UFS 6-3 and UFS 6-5).

this is the best I am attaching the original and the false colors (old CS6 action ... more magenta)

I spent the day trying to replicate a photo I saw on Photoni's flickr page.... Nearly got there ? Here I show the raw converted to .jpg, then a channel swap, RGB to BRG. I can't work out what I have to get the raw to look like to end up with this yellow that photoni got, instead of the greenish yellow that I have ended up with ? Raw to .jpg..... Swap RGB to BRG

First take of the BG3- / BG25- filter stack comparison. White balanced for a pleasing result. The BUG3 filter-stack normally consists of S8612 and BG3, both 2mm, but there is an alternative blue filter that gives a similar, but not identical result, BG25. This is a comparison to show the differences. WB against PTFE often gives a weird tinted result. See Second take below. Images to the left or first ( S8612, 2mm + BG3, 2mm ). Images to the right or last ( S8612, 2mm + BG25, 2mm ). The same unknown buttercup I used next day for focus stacking. https://www.ultravio...5-filter-stack/ In VIS it is yellow. Cherry blossoms collected late March 2020, from a tree just outside the house where live. In VIS they are pink. Sometimes I prefer the results I get from the BG25-stack as it gives a wider range of green nuances and often are WB better to a pleasing result. Second take of the BG3- / BG25- filter stack comparison. White balanced against PTFE. It i interesting to note that for the BG3-stack some parts of the yellow flower (red in the pictures), with specular reflection are white just like the WB-target. The tinted result of the cherry blossoms is typical for most blue, pink and white flowers, while yellow flowers are less affected, compared to those in the first post. Lessons learned here is that there is no correct WB for these types of filter-stack. These are false colours. How to WB depend on what you are trying to enhance or show. Images to the left or first ( S8612, 2mm + BG3, 2mm ). Images to the right or last ( S8612, 2mm + BG25, 2mm ). WB @ PTFE

About 6 years ago I posted some results about stacking a BaaderU UV-Pass with certain other filters in an attempt to test for Visible or Infrared leakage through the BaaderU. These tests involved making long exposures to "force" unwanted Vis or IR through the BaaderU stack. Note: I am not revisiting this topic to discuss the validity of this kind of forcing test for finding unwanted light leakage. Please don't veer off into that area after I ask my question below. Here's the linkie to the original topic. Filter Test: BaaderU UV-Pass Date: 03 May 2015 Now I'll repeat a result from that linkie so we have it handy before I ask my question. Filter Stack: BaaderU UV-Pass + B+W 092 IR+Red Pass Filter Test for any IR or red leak during a 10 second exposure at ISO-200 in sunlight. Subject: 5 Spectralon standards Equipment: UV-Nikkor 105/4.5 + D600-broadband + Sunlight Photo of all 5 standards straight out of camera with no edits. f/8 for 10 sec @ ISO-200 This is clearly black. In case you don't believe there were 5 standards in there, then here is that photo with a full 3 stops more of exposure. This was not in the original topic. Here is the raw composite of a crop from that forced exposure. The crop was made over the white standard in the middle. In the original topic I then concluded after this photo that: "Pushed 10 second exposures show that very little Red/IR was recorded." . The assumption in my conclusion was that I was seeing a negligibly small amount of IR leakage through the UV-pass BaaderU during the 10 second long exposure. It is a sensible assumption because we know that most UV-pass filters made from dual bandpass (UV+IR) substrates can be a bit weak between 700 - 800 nm. However........ QUESTION: Have we ever ruled out the possibility of Ultraviolet leakage through IR-pass filters either by experiment or by referring to any existing transmission data for IR-pass filters? Do either the Schott or Hoya IR-pass data sets go low enough to indicate UV leakage around 350nm? If there were any minor UV leakage through an IR-pass filter, we would never see it when using a singleton IR-pass filter because the amount of IR would be so large. But for the stacked UV-pass and IR-pass in the original experiment, how do I know which filter was the blocker and which the passer? Maybe both filters were leaky? Any thoughts or references would be appreciated.

Recently I was shooting a sunflower for the botanical section using an SB-140 UV-flash. As a side note I made these raw composites in Raw Digger in order to see the non-white-balanced colors for the three UV-pass filters I was using. I've made lots of posts before about raw colors for different filters. I will try to find the links and post them here in case anyone is interested in this. I am rather fascinated by the idea of the non-white-balanced colors our cameras are actually recording under different UV, IR or UV+IR filters, but it might be total Boresville for some (many?). LINK: This is a link to photos showing the non-white-balanced colors of 36 UV/IR filters. It does not include raw colors for two filters in this current topic (U340 x 4.0mm and AndreaU Mk-II). https://www.ultravio...white-balanced/ ADDED LATER: I was not going for a comparison, per se, between filters using the photos shown below. I only intended to post some raw color illustrations for the filters I was using during the sunflower shoot. See Cadmium's Post #4 below for a comment about comparability of filters. I agree with that comment. Also I don't think the raw color for the AndreaU Mk-II had ever been posted before, so there's that too. The AndreaU-MkII for this flower was about 15° which I would call red-orange if you accept orange as being at 30°. The BaaderU was at aboug 19° which is a little bit more orange. And the unblocked 4mm thick U340 was almost entirely orange at 28°.