aphalo Posted August 14, 2022 Share Posted August 14, 2022 2 minutes ago, colinbm said: I have asked Tamgsinuo in the past to have an actual spectrum of a particular filter, but I only got the advertised chart. Good to know! I haven't ever asked for measured spectra from them. With Tangsinuo's published plots and those of most other eBay and AliExpress sellers it is not always clear whether they show total transmittance or internal transmittance for the ZWB-series filters. Comparing my measured spectra for ZWB1 and ZWB2 to the plot you added from Tangsinuo the actual filters have lower transmittance in the UV but also block IR better. Maybe Tagsinuo's plots show internal transmittance or a different glass thickness... Link to comment
colinbm Posted August 14, 2022 Share Posted August 14, 2022 I just warn to be wary. Nothing is what it is from the Orient. Link to comment
aphalo Posted August 14, 2022 Share Posted August 14, 2022 One needs to be careful with any on-line purchases, indeed! One needs to carefully check what one receives and complain if needed. This is tricky with filters if one does not have access to measurement equipment. I am specially wary of electronics to be connected to mains power or power banks and the like, as a failure in them implies risk of fire or death. Counterfait (or re-labelled) electronic components are also common. Purchased things can also be just fine but not always much cheaper than bought within EU. In eBay not only sellers from the Orient are unreliable, and not all sellers from the Orient are unreliable. Neither all AliExpress sellers are unreliable. In fact, in my experience if one is ready and able to use the safeguards provided, AliExpress can be a safer place to buy than the oriental manufacturers' own web stores. Link to comment
ulf Posted August 14, 2022 Share Posted August 14, 2022 Filters from different batches made in China will very likely have a bigger spread. There is no guarantee that they follow the published transmission graphs, but then the costs are much lower and that makes it more attractive to try them out. However there are very little guaranteed about the transmission from proper manufacturers like Schott either. Just as Aphalo points out their graphs are showing typical average performance. The guaranteed values are given at a few wavelengths only. As long as these parameters are fulfilled a filter glass material batch will be qualified as OK. Look at the "Spectral values guaranteed" at top right in these data sheets: https://www.schott.com/shop/advanced-optics/en/Matt-Filter-Plates/S8612/c/glass-S8612 https://www.schott.com/shop/advanced-optics/en/Matt-Filter-Plates/BG39/c/glass-BG39 It is clear that the S8612 is mainly an IR-blocker and that the UV-performance might be deviating more as it is not in any way guaranteed. The BG39 is specified at 405nm and 350nm and will be better controlled at the UV-side and might not be that bad as an alternative IR-blocker. My favourite S8612, 2mm that I bought from Steve (Cadmium) a long time ago has the nice deeper good UV transmission seen in the typical graphs. Later I have bought have a few S8612 from different sources made from more recent glass melts. The companies they came from are professional suppliers and I am confident that they really are made from Schott glass. These filters have a less prominent deeper UV transmission, but still within the Schott specifications. They still perform a bit better than the BG39, but the difference is not as dramatic as seen in the typical transmission graph. When comparing the image results and exposure times using the different S8612-filters, in the same photo shooting session, it is almost impossible to tell the difference. The reason for this is that the upper UV-part will be the dominant one due to more sensor sensitivity. Link to comment
photoni Posted August 14, 2022 Share Posted August 14, 2022 2 hours ago, ulf said: When comparing the image results and exposure times using the different S8612-filters, in the same photo shooting session, it is almost impossible to tell the difference. The reason for this is that the upper UV-part will be the dominant one due to more sensor sensitivity. @ulf Right ! @aphalo I took the liberty of assembling your charts it seems that the combination of your ZWB1 + QB21 filters is great, logically the Baader U2 is the best and costs like 10~15 Tangsinuo I then pasted your graphs and the Chinese ones ... they are different but the substance is similar last "fusion" it is a pity that S8612 is missing I'll probably take a 2mm thick QB21 in its place, hoping it cuts reds as well as yours. (I'll try it with QB29 instead of TSN) P.S. your chart of the QB21 (~ BG38) looks similar to the BG40 (which tangsinuo doesn't have Ø52) P.S.2 Another filter that cuts reds well is the BG18 . I had a 2mm thick, rimless DDR version ... but I broke it Thank you Link to comment
ulf Posted August 14, 2022 Share Posted August 14, 2022 1 hour ago, photoni said: @aphalo I took the liberty of assembling your charts it seems that the combination of your ZWB1 + QB21 filters is great, logically the Baader U2 is the best and costs like 10~15 Tangsinuo Unfortunately QB21 and BG38 do not suppress IR good enough for UV-photography. They are good for restoring a full spectrum camera for VIS photography, but not for UV-photography. In some cases BG40 2mm will do, but just barely and only if you have a really good UV-capable lens and a camera with good UV-sensitivity. For UV-photography more IR rejection of the peaks around 700nm is needed. Then there are BG39, S8612 and some other alternatives that I have not measured. I decided that I was saturated with BG-type filters and saw no need to buy TSN575 just to measure it, when it became available. I am open to measure filters sent to me, if the sender also pay the return shipping and accept the shipping risk. Link to comment
Yves W Posted August 14, 2022 Share Posted August 14, 2022 Thank you very much Aphalo it is very good and very complete. Thank you all for your valuable advice. Since 2009, I have been using the SCHOTT BG39 3mm and UG1 2mm filters in 50x50mm purchased from UQG Optics with AF-1, then the Baader U since 2012. To study other filters, I tried Chinese filters ZWB1, ZWB2, ZWB3, ZB1, ZB2, QB5, QB29 with different BG39, BG38, etc. Now I have made my choice and I will go for a false color bee vision with a U330 with S8612. Chinese filters make it possible to approach different filters at modest prices. Link to comment
Fandyus Posted August 14, 2022 Author Share Posted August 14, 2022 Some great information in this thread so far, thank you! I am sorry to not have replied to everyone individually as I got a little overwhelmed with the interest in this post. Especially thank you, Toni and aphalo for sharing such valuable data with us. It is a huge help. I am still indecisive on what to order, currently unsure whether the AR coated QB21 is worth it, since I'm not sure how much worse IR and red suppression it has compared to my QB39. Cheers. Link to comment
Andrew Dayer Posted August 14, 2022 Share Posted August 14, 2022 On 8/12/2022 at 11:45 AM, lukaszgryglicki said: I'm hunting for a longer time without luck... Forgive my ignorance and not to go off-topic but what's the issue with SCHOTT S8612 - stock availability or getting circles made / mounted? Link to comment
ulf Posted August 15, 2022 Share Posted August 15, 2022 I did some measurements of my Tangsinuo QB21 2mm and BG39, stacked with ZWB1 2mm and with ZWB2 2mm. Measurement setup: Ocean Optics Flame-S array-spectrometer. Test path: collimated light beam with Avantres UV collimators. (there are no reason what so ever to use an integrating sphere as the filter glass is flat) Light source: Mikropack DL-2000-BAL with deuterium and halogen lamps. Here are the results showing Ttot, total light transmission including all losses from surface passages, not directly comparable with many graphs presented here of theoretical inner transmission, Ti QB21-stacks: It is very clear that The QB21 is not at all suited as an IR-blocker for UV-photography. BG39-stacks: Unfortunately I do not have two ZWB1 2mm to answer this thread's original question. However I measured the ZWB1 alone and the IR-peak is at OD 0.8. I think a stack of QB21, 2mm and 2 x ZWB1, 2mm would get slightly more than OD 3.0. I think that would be a marginal IR suppression for UV-B imaging if the light source has much IR-content, as sunlight. Link to comment
Yves W Posted August 15, 2022 Share Posted August 15, 2022 Fandyus, rather than QB21=BG38, as I had 2 QB39=BG39 of 1.5mm unusable, I put them in a single ring and it's good for cutting IR under UV with ZWB1 or ZWB2, inexpensive palliative solution. A few years ago, I found very good Chinese BG39s but I don't know where. Thank you all very interesting. Link to comment
Unscenerie Posted August 26, 2022 Share Posted August 26, 2022 Aphalo, you demonstrated that Tangsinuo 1.6mm QB21 AR + 3mm ZWB2 is only marginally usable. Fandyus thought about using 4mm ZWB1 + 2mm QB21 – I'm wondering what the transmission would look like. Would it transmit deeper into UV compared to, let's say, a 2mm ZWB1 + 2mm TSN575? Would a stacked QB21 (e.g. 4mm) remove IR and still provide deeper reach into UV than TSN575? I should note that somehow, I ended up with a 3mm Tangsinuo ZWB1, which could potentially be combined with QB21, but I'm not sure if Tangsinuo still sells it. More importantly, I messaged Tangsinuo about a 2mm BG39 (since he only offers 1.5mm BG39), and he replied, "There is no 2mm BG39 yet. I will arrange to produce some." I'll let you know if it becomes available. Link to comment
photoni Posted March 11, 2023 Share Posted March 11, 2023 today I measured the thickness of my 52 mm diameter filters it is very strange that there is no uniformity Tangsinuo filters QB39 - 1.6 mm thick (~BG39) TSN575 - 2.25 mm thick (~BG39) QB29 - 2.1 mm thick (~BG25) ZWB3 - 2.15 mm thick (~UG5) ZWB2 - 2.15 mm thick (~UG1) ZWB1 - 2.2 mm thick (~UG11) Toshiba Red - 2.3 mm thick Hoya R72 - 2.45 mm thick Link to comment
ulf Posted March 11, 2023 Share Posted March 11, 2023 2 hours ago, photoni said: today I measured the thickness of my 52 mm diameter filters it is very strange that there is no uniformity Tangsinuo filters QB39 - 1.6 mm thick (~BG39) TSN575 - 2.25 mm thick (~BG39) QB29 - 2.1 mm thick (~BG25) ZWB3 - 2.15 mm thick (~UG5) ZWB2 - 2.15 mm thick (~UG1) ZWB1 - 2.2 mm thick (~UG11) Toshiba Red - 2.3 mm thick Hoya R72 - 2.45 mm thick That is an interesting series of measurements. It might indicate that the assumed thicknesses like 2.0mm are not quite consistent for different filters. @Tony: How accurate do you think your measurements are? If you have used the wooden spacer pieces, with rather rough surface that you showed in another thread, there might be some variability. Also wood change in dimension depending on humidity. Different thickness is a way to tune the transmission and in some cases, especially for the last two that might be intentional. Link to comment
photoni Posted March 11, 2023 Share Posted March 11, 2023 4 hours ago, ulf said: @Tony: How accurate do you think your measurements are? If you look at the previous measurements, they are all different from these, but only slightly, 0.05 mm, it is logical that the wood fibers are in different positions, and have a small difference. I have been using the tool for 50 years, it is reliable :) Link to comment
dabateman Posted March 11, 2023 Share Posted March 11, 2023 8 hours ago, photoni said: today I measured the thickness of my 52 mm diameter filters it is very strange that there is no uniformity Tangsinuo filters QB39 - 1.6 mm thick (~BG39) TSN575 - 2.25 mm thick (~BG39) QB29 - 2.1 mm thick (~BG25) ZWB3 - 2.15 mm thick (~UG5) ZWB2 - 2.15 mm thick (~UG1) ZWB1 - 2.2 mm thick (~UG11) Toshiba Red - 2.3 mm thick Hoya R72 - 2.45 mm thick Why is that strange? These Chinese filters will have variations and may be extras from specific requests. + or - 0.1mm is what I would expect. Link to comment
ulf Posted March 11, 2023 Share Posted March 11, 2023 1 hour ago, dabateman said: Why is that strange? These Chinese filters will have variations and may be extras from specific requests. + or - 0.1mm is what I would expect. ±0.1mm in thickness difference is often not that critical for filter transmission. The difference between melts of the glass material can give more variations. So far the thickness variation of my filters from Tangsinuo has been quite good. They deviate less from stated nominal thickness values than filters from a known American quality filter supplier. Inspired by Tony's measurements I spent a few hours measuring some of my most used filters. I used a digital micrometer-tool with a 1um resolution. I think it is quite good , but I have no traceable reference bits to confirm absolute accuracy. My guess is that it is at least good to ±2um UVIROptics 52mm filters Filter type Thickness: nom. actual Schott S8612 2mm 2.020mm Schott S8612 AR Coated 2mm 2.000mm Schott BG38 2mm 2.107mm Schott BG25 2mm 2.112mm Schott BG25 #2 2mm 2.111mm Schott BG3 2mm 2.020mm Schott UG5 1mm 0.929mm Schott UG5 1.5mm 1.461mm Schott UG2A 2mm 2.063mm Schott UG2A 1mm 1.159mm Schott UG2A 0.7mm 0.709mm Schott UG1 1mm 1.060mm Hoya U360 2mm 2.124mm Hoya U330 2mm 2.051mm Hoya B410 3mm 3.026mm Tangsinuo 52mm filters Filter type Thickness: nom. actual ZWB1 8.0mm 8.072mm ZWB3 2.0mm 1.958mm ZWB3 2.5mm 2.533mm ZWB3 3.0mm 3.042mm GRB3 2.0mm 2.053mm QB21 AR 2.0mm 1.959mm QB29 1.5mm 1.517mm ZB1 2.0mm 2.041mm ZB2 1.5mm 1.533mm ZB2 2.0mm 2.041mm 77mm filters ZB1 2.0mm 1.999mm QB29 1.5mm 1.514mm QB29 2.0mm 2.067mm TZN575 2.0mm 2.026mm Link to comment
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