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Chinese filters - a positive experience

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#1 JMC

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Posted 20 July 2021 - 15:22

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...ss_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.
Attached Image: 20210720_134153.jpg

Also, one of the 77mm filters in its ring and supplied case.
Attached Image: 20210720_133836.jpg

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).
Attached Image: ZWB1 and 3 camera filters.jpg

Attached Image: ZWB1 and 3 3mm 200by200mm.jpg

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.
Jonathan M. Crowther

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#2 Stefano

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Posted 20 July 2021 - 15:49

I recently bought 2× 2 mm thick ZWB1 filters (52 mm) from them. Nice to have a measured transmission graph (aasuming there is little variability).

I bet those 200 mm squares are heavy! That's a lot of glass.

#3 Fandyus

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Posted 20 July 2021 - 15:58

Yeah, the striations can be an issue. I even talked about them to Mr. Jason Li which is the person who you probably negotiated the deal with and he flat out said the striations can't be prevented sometimes and that they don't refund them. One of the filters I have from Tangsinuo has one striation that is visible in the images while stopped down, decreasing sharpness. Other filters from them that I have are perfect. I recently made a bigger order from their AliExpress. 52mm 2mm thick filters made of ZWB3, GRB3 and ZWB1, plus a 55m cyan dichroic gobo projector filter for emulation of aerochrome. Finger crossed those are all okay.

But anyhow, enjoy your new toys. For filtering flashes, chinese substrates really are the superior solution. I am considering getting some for my full spectrum flash, to use for UVIVF. But I might just get one of those powerful filtered LED flashlights instead. I have my sights set on something like this. https://www.aliexpre....14da2e0epanekJ
Should be enough power for any reasonable user.
Edit: though looking at the ratings of the seller which are only around 90% positive, I'll probably have to look for something else.
Edit II: I might make a post about picking a good flashlight for this actually. I want as much power as possible and I'm willing to pay up. 50-100 USD for sure.

Edited by Fandyus, 20 July 2021 - 16:11.


#4 UlfW

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Posted 20 July 2021 - 16:28

View PostStefano, on 20 July 2021 - 15:49, said:

I bet those 200 mm squares are heavy! That's a lot of glass.
They weigh around 470g each.
Ulf Wilhelmson
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#5 Stefano

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Posted 20 July 2021 - 16:31

So almost 1 Kg of glass for the pair, considering he has four pieces that's almost 2 Kg. That's heavier than I thought.

#6 UlfW

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Posted 20 July 2021 - 16:36

Stefano, as you were picky about how to write units, it is good to know that the thousand prefix kilo is written as k, not K. :wink:
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#7 UlfW

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Posted 20 July 2021 - 16:43

I have bought optical filters from Tangsinuo for several years.
They have always had excellent service and all glass material has been good so far.
Their packaging has always been superb.

Some of the first filters I got a long time ago had rounded edges due to the way they processed the glass rounds.
That was not a big problem as it was close to the edge and not in the active light path.
Filters made the last three years has not had that flaw.
Ulf Wilhelmson
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#8 Stefano

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Posted 20 July 2021 - 16:43

Oh yes, that's true. And I even knew that, it is the only prefix that "increases" the quantity of something which isn't upper-case. I forgot that.


#9 Andy Perrin

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Posted 20 July 2021 - 18:24

I think the conclusion I would draw is that we shouldn't condemn all varieties of the Chinese-made filters out of hand, we should instead go by manufacturer.

#10 Fandyus

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Posted 20 July 2021 - 18:58

View PostAndy Perrin, on 20 July 2021 - 18:24, said:

I think the conclusion I would draw is that we shouldn't condemn all varieties of the Chinese-made filters out of hand, we should instead go by manufacturer.
True, but as I said, Tangsinuo isn't perfect either.
Not to diss them, they're the guys who enabled the less rich of us (such as myself) to take pure UV pictures. And they're my go to supplier.
Check my first comment to see what I mean.

#11 colinbm

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Posted 21 July 2021 - 03:06

Thanks for the post & specs Jonathan
I am waiting for some ZWB1, 100 x 75 x 8mm, to filter the UVB LEDs , to arrive next week ........ :grin:

#12 JMC

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Posted 21 July 2021 - 09:29

All, thanks for the comments.

In this circumstance it looks like I did well - Fandyus, thanks for mentioning about the striations, I will will remember to ask them about that for any future orders. Frankly, saying they don't replace or refund for striations is not acceptable - if it has striations don't sell it, unless it is being sold at a reduced rate.

Andy - looks like it can still be lottery with regards to quality (see comment from Fandyus). I suppose my 'take home' from it is that if you have means to be able to test something that you are receiving, then these Chinese filters can offer a cost effective was to get UV suitable filters. I'm always thinking 'what do I need for publishing my work?'. With Schott glass it would be enough to quote the filter type and thickness as there are enough sources of information which could produce the transmission spectra from that. However for these ZWB filters, I still wouldn't be comfortable just doing that and would want to include actual transmission spectra on the filters I've used.

Col - wow, 8mm thick. Is that being done as a single piece? If so, good to know the can make really thick ones if needed. 8mm by itself will offer pretty good blocking for everything from 400nm upwards.

I'm sort of wishing I'd bought a ZWB3 1mm (or even thinner if it could be done) in 77mm diameter and had everything sent at once. Maybe with a future order.
Jonathan M. Crowther

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#13 colinbm

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Posted 21 July 2021 - 09:54

" Col - wow, 8mm thick. Is that being done as a single piece? If so, good to know the can make really thick ones if needed. 8mm by itself will offer pretty good blocking for everything from 400nm upwards. "

Thanks Jonathan, yes Jason did a double take, but I told him that Dave sent me, & he didn't argue anymore after that.... :rolleyes:
PS, I want it for the UVB 309nm LEDs as they leak some visible light.

Edited by colinbm, 21 July 2021 - 09:58.


#14 JMC

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Posted 21 July 2021 - 10:39

Hi Col, even 2mm ZWB1 offers pretty good filtering of visible, so 8mm should be very impressive.

Going from 2mm to 8mm, you are doubling the thickness and then doubling it again. As a basic calculation, here's what it should look like based on my data for the 2mm thick one.
Attached Image: ZWB1 2mm magnified and 8mm calc.jpg

This is a simplification as I've not taken into account the reflection from the surfaces but you get the idea.
Jonathan M. Crowther

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#15 colinbm

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Posted 21 July 2021 - 10:56

Yep, that is what I want to see, or rather what I don't want to see, is any visible, Thanks for this Jonathan.

PS the LEDs don't have any IR, so that is not a problem.

Edited by colinbm, 21 July 2021 - 10:57.


#16 Stefano

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Posted 21 July 2021 - 15:31

Just an observation, with 8 mm of Hoya U-340 glass you have OD 5+ in the far red region, while with Jonathan's simple calculation you have less than OD 3. This type of graph is very sensitive to the precision of the measurement at 2 mm as you amplify any error by calculating a thickness of 8 mm.

An 8 mm thick U-340 filter has enough blocking for UV-only photography, as Steve showed.

The LEDs Colin has emit some visible and probably some near-infrared light, but they may emit some UVA too. 2-4 mm of ZWB1 should be enough to filter any non-UV contamination, but they can't help with UV contamination (if present). With my camera and a UVA pass filter (ZWB2 + "BG39"), I saw UVA emitted by my 265 nm LEDs. I am sure it wasn't UVC, my camera is probably not sensitive there and also the filters I used blocked UVC. So this may be an issue.

#17 Andrea B.

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Posted 21 July 2021 - 21:52

Yeah, the striations can be an issue. I even talked about them to Mr. Jason Li which is the person who you probably negotiated the deal with and he flat out said the striations can't be prevented sometimes and that they don't refund them.

Hmmm....There's something wrong with Mr. Li's declaration. It might be that striations cannot be entirely prevented, BUT a badly striated filter does not need to be sold to a customer. You don't get badly striated filters from B+W or from Hoya or from Schott or from Tiffen. I would find another supplier.

Read all about striae and how Schott optimizes their glass during production here: Striae_in_Optical_Glass_Eng.pdf
In particular, see Section 7 which discusses at length the effect of striae in an optical system. This is a very interesting chapter.

The C grade referred to in the excerpt is Consumer grade.

Excerpt:

The specification in the current SCHOTT catalogue [6], in general, excludes striae with grades higher than C. This is because such striae is prevented during the production process with the exception of a thin layer (< 3 mm) lying directly below the fire polished surfaces which originates from the evaporation of constituents during casting. These layers are eliminated in the subsequent machining process steps. SCHOTT’s normal quality is always class C or better per 50 mm path length, corresponding to about 30 nm optical path difference. Therefore, SCHOTT standard optical glass fulfills the requirements of the ISO 10110 class 1-4.

The usual disclaimer: The preceding Schott link is for your information only. Neither I nor UltravioletPhotography.com has any business/monetary association with Schott or with any filter vendors.
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#18 Fandyus

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Posted 21 July 2021 - 23:52

Since a few people have taken note of what I said about Tangsinuo and their stance on striations, here are screenshots of what Mr. Li said. The messages were right after one another, but I said something inbetween. Hence I have two screenshots.
This is from my conversation with him via AliExpress.
Attached Image: Screenshot 2021-07-22 at 01-46-59 Alibaba Manufacturer Directory - Suppliers, Manufacturers, Exporters Importers.pngAttached Image: Screenshot 2021-07-22 at 01-47-15 Alibaba Manufacturer Directory - Suppliers, Manufacturers, Exporters Importers.png
Edit: I do wonder what would happen if I decided to dispute a filter that came with striations. They do not warn that it's a possibility in their product descriptions so maybe one could win the case. Though I'm not sure if it would be worth it to send the thing back to China with your own money, as it would probably cost more than the filter itself.

Edited by Fandyus, 21 July 2021 - 23:54.


#19 Fandyus

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Posted 21 July 2021 - 23:59

View PostJMC, on 21 July 2021 - 09:29, said:

In this circumstance it looks like I did well - Fandyus, thanks for mentioning about the striations, I will will remember to ask them about that for any future orders. Frankly, saying they don't replace or refund for striations is not acceptable - if it has striations don't sell it, unless it is being sold at a reduced rate.
No problem. I'm glad to have mentioned this. It's unfortunate but it changes nothing about the fact that I do not have the funds to go to Schott or Hoya, so Tangsinuo it is. A lot of the branded filters are more expensive than the camera I would be mounting them on..

#20 Cadmium

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Posted 22 July 2021 - 00:08

Andrea, Interesting post about striations. These are also found with Hoya and Schott filter glass. Also other surface problems like pits.
They don't refund for such defects, but I don'[t consider those quality material, and not generally used like you say in the end product. Such quality is then part of the price of some filters given any wasted material.
Certain types of filter glass tend to have defects more than others, for example U glass is pretty prone to such, and most other filter glass like longpass glass (especially visual range) tend to be free of defects.
It is something I have to watch for constantly and work around. A surface pit may not show at all in a photo, but it is like getting a new car, you want the filter to good and look new.

Edited by Cadmium, 22 July 2021 - 00:11.