New Tangsinuo filters - which to get?

[Fandyus]

Hello,

I was planning to buy a few Tangsinuo filters I don't yet own, namely a TSN575 with it's superior red supression. I was also thinking of buying a QB21, it is a new offering of theirs and it is supposedly multi coated, which prevents corrosion and increases transmission. It supposedly has a better transmission at the lower end of the UV spectrum compared to the QB39 I already have. But I'm generally not sure if it's worth it. Lastly I want to get a second ZWB1 for a thicker stack, but supposedly with a TSN575 I don't need a thicker stack to not have leaks with ZWB1's weaker red supression? But TSN575 has worse transmission in the lower UV wavelengths which is generally the anthithesis of what the ZWB1 is used for.

Basically what I mean is, would it be better to use the 4mm worth of ZWB1 with the QB21, or the thinner 2mm ZWB1 with a TSN575?

I want to get this stack to better utilize the light from my reptile UVB 15.0 bulb.

Edit: methinks the TSN575 could be good for UV+blue type stacks, maybe with a ZWB3 or deep blue type glasses.

[Yves W]

Hello Fandyus,

For these IR cut filters:

- The QB21=BG38, I read that it cuts a little UV, so I put it on the Zeiss T for RGB and UVIVF

- For the ZWB1, I use a QB39=BG39 2.3mm

- For the ZWB2, I use QB39=BG39 3mm (1.5+1.5 single ring)

- For the ZWB3, I use the TSN575

The QB21 cuts UV and the BG39 1.5mm from Tangsuino is very thin.

[Ming]

4 hours ago, Yves W said:

Hello Fandyus,

For these IR cut filters:

- The QB21=BG38, I read that it cuts a little UV, so I put it on the Zeiss T for RGB and UVIVF

- For the ZWB1, I use a QB39=BG39 2.3mm

- For the ZWB2, I use QB39=BG39 3mm (1.5+1.5 single ring)

- For the ZWB3, I use the TSN575

The QB21 cuts UV and the BG39 1.5mm from Tangsuino is very thin.

Yves, you put two BG39 1.5mm filters in a single ring.  Is it okay to combine any two filters in one ring?  What I have in mind is to combine either ZWB1 or ZWB2 with either BG39 2.3mm or TSN575.  The issue is when two filter rings are stacked on a wide-angle lens, I get severe vignetting.  Thank you.

 

[Andrea B.]

Yves, thank you for this recommended list of toppers for each type of ZWB glass. I'm a bit deficient in my knowledge of ZWB and its acronyms, so this will be useful to UVP readers. I'm going to also incorporate it into some recommended lists -- with a credit going to you. 

[colinbm]

My only question is, are these suggestions based on the Chinese graphs or are they based on 'ACTUAL' spectrograph readings ?

[photoni]

Constant and stable production would be needed, but as they cost much less than Schott etc, there will be many variations in thickness and transmission.
Starting from this assumption, and since I don't have the tools to measure mine, I took a diffraction grating. and with a stable light ... the flash I did these empirical tests.
it is clearly seen that the 1.5mm thick QB39 is not enough to cut red and IR
the TSN575 works very well, but cuts off a part of the "green" which is presumably 340 nm.
If any of you find a S8612 Ø52 at a good price in Europe please let me know.
Thank you

Antonio

[Yves W]

I assembled the 2 BG39 1.5mm for convenience.

The assemblies were made according to the curves and tests I saw on UVP. No scientific evidence.

I note that the ZWB2 with the BG39 1.5+1.5 looks like my Baader U at the rendering and WB level.

Like Antonio, if S8612 in 52 in Europe, I am a buyer.

Thanks Antonio for the transmission very good

 

[lukaszgryglicki]

if S8612 in 52 in Europe, I am a buyer

I'm hunting for a longer time without luck...

 

[photoni]

I assembled the 2 1.5mm BG39s + ZWB1… the result is similar to TSN… cuts the green.  I don't have any premium filters, but I would be willing to buy a 2mm thick S8612
thanks Yves

[Yves W]

Antonio, you write the TSN575 cuts the green, but in your transmissions we see it and we also see it with the ZWB3.

The TSN575 cuts the IR like the BG39 2.3 or 3mm.

The curves are also good for the green of the TSN575.

It is not good for UV around 340.

I was very inspired by your tests for my choices, thank you.

[dabateman]

19 minutes ago, Yves W said:

Antonio, you write the TSN575 cuts the green, but in your transmissions we see it and we also see it with the ZWB3.

The TSN575 cuts the IR like the BG39 2.3 or 3mm.

The curves are also good for the green of the TSN575.

It is not good for UV around 340.

I was very inspired by your tests for my choices, thank you.

Photoni means the extreme green UV edge on the left. TSN cuts IR well, but doesn't have a great deep UV transmission bump like S8612. Its more like BG39.

Reed bring back his liquid copper sulfate filter may be an option for European folks. It looks to have excellent IR cutoff, better than S8612 and it has a deeper UV bump than S8612. Just don't freeze it. 

[lukaszgryglicki]

Yep, can't wait for it, to use it as IR blocker with my U-340 (4mm) instead of BG39 2.3mm and/or S8612 - should allow deeper UV.

Also CopperU seems interesting (it is a stack with copper sulfate with "something" that seems quite similar to U-340 2? mm).

 

[photoni]

On 8/12/2022 at 2:51 PM, Yves W said:

Antonio, you write the TSN575 cuts the green, but in your transmissions we see it and we also see it with the ZWB3

by "green" I meant the left end

 

I have added a photo with a neon light and a graphic found here: LINK

they are probably not perfectly synchronized with the ZWB1 graph

 

 

[Yves W]

Sorry. We agree, I confused it with green on the right. The TSN575 is not good on the left and should be avoided in pure UV.

Thanks

[aphalo]

Hi. I do have these filters and I have measured their transmission spectra. Measurements were done with an old Hewlett-Packard 8453 UV/VIS array spectrophotometer, with Deuterium and Tungsten lamps switched on. The noise floor is about 3.5 OD and readings are stable after warm-up, so spectra are reliable but minor leaks are not visible in the spectra. Measurements are of total transmittance (no filter used as blank or "air") and done without an integrating sphere.  The internal transmittance spectrum from Schott specifications has been converted into total transmittance using the correction factor supplied by Schott as part of the specifications. (Andrea: I add the figures here but feel free to move them, or if you prefer I can write a separate post.) The data will be included in the next version of R package 'photobiologyFilters' that I hope to be able to submit to the CRAN repository in about one month's time.

 

The figures are labelled with supplier, filter type, mounting ring size and, in brackets, glass thickness.

 

[colinbm]

Thanks for doing these aphalo.

[aphalo]

I add here two simulated stacks and spectra for my copies of Bader U and of StraightEdgeU Mk I, measured with the same spectrophotometer. Light beam almost normal to filter. I haven't yet done much testing on camera, but from the spectra it looks like any comparison will be affected by the lens and possibly also camera used.

[Added some hours later] Do have a look at the topic Filter Transmission Charts #2. The simulations shown below are only a rough approximation and done by simple convolution of the T spectra, ignoring multiple reflections.

 

[colinbm]

Again thank you aphalo

[photoni]

it is with great pleasure that I see this yours work.
thank you very much aphalo !!!

[aphalo]

Happy to share! Your are welcome.

[aphalo]

Reading the thread in Filter Transmission Charts #2 got me thinking how much could be the error in the simulations shown above. I had in fact measured on the same session the transmission of the stacks, but had not yet plotted them. So, here they are measured with each filter in its own ring and screwed together. The difference between simulation and measurement is rather small, but visible in the plots.

I also tested stacking ZWB1 and ZWB2 with QB21 AR coated. These stacks leak near 700 nm, with OD < 3 at the "cross-over" of the cut-in and cut-off tails.

The leak is barely visble in the plots above, but a change of scale range to 0 to 1% T reveals this clearly.

I did not measure but instead simulated the same stack with ZWB1 and ZWB2 at 3 mm and QB21 AR 1.5 mm, using measured spectra for the individual filters. I used here filters that I actually have in 30.5mm frames.

The leak is not visble in the plots above, but a change of scale range to 0 to 1% T reveals it clearly.

 

Just about 3 OD, so only marginally usable, I would think.

 

[colinbm]

Excellent work aphalo

[colinbm]

And just so we can compare with Tangsuino advertised graphs on eBay.....

ZWB 1, 2 & 3

 

TSN575

 

QB21

 

QB39

[aphalo]

One thing to keep in mind is that as can be seen in the first of my plots, there is variation from glass melt to glass melt. So, those two QB21 AR filters I bought at the same time in different sizes differ in their transmission spectra. Tamgsinuo's AliExpress plots (as well as Schott's specifications) are "typical" rather than guaranteed. Tangsinuo listings tell in many cases that if the spectrum is critical to your use, they can send the actual measured spectrum for the filter. Differences between published and actual transmission spectra are to be expected.

 

The spectra I measured for AR coated QB21 show that this coating increases total transmittance by decreasing reflection.

[colinbm]

I have asked Tamgsinuo in the past to have an actual spectrum of a particular filter, but I only got the advertised chart.