What is everyone doing with their 8mm ZWB1

[Andrea B.]

Nice sparticle test, Col.

 

Andy, yours is just looking like a bad glass thing. Can you see anything at all unusual when the light hits the ZBW1 x 8.0mm in different directions?

[colinbm]

Same white balance?

 

This is what I would expect. No 390 nm, and more green at 340 nm. You can really see how the curve shifts towards shorter wavelengths with the 8 mm thick ZWB1.

 

Yes Stefano

I did a CWB with the BaaderU, then added the rest to see the changes when I added the 8mm ZWB1.

[ulf]

I got some time earlier to make reasonably proper transmission measurements of my ZWB1, 8mm glass.

Here, finally I have all the raw data processed for proper displaying.

 

Eventually I will make a more formal specific topic for this filter to have all data well collected.

 

 

The real transmission values from 390nm to 440nm is likely lower.

This is a difficult range for me to measure deep OD.

It is in a transition area between two light sources and influenced by strong light in nearby wavelengths due to crosstalk.

 

It looks like this ZWB1-material is optically less dense than UG11 and U-340.

That gives a very good UV-transmission, but also a higher IR-peak.

The OD in IR is in the same range as the one by my Baader U.

Compared to any BG-glass based stack it has a much deeper UV-reach.

[colinbm]

Thanks very much Ulf.

[Stefano]

Ulf, thanks for your measurements. If you have time, you could scan your 2*4 mm thick U-340 filter to measure its real transmission (we only have the calculated one) and make a comparison. OD calculations at 8 mm thickness are sensitive to errors if the data was measured at 2.5 mm.

[ulf]

Ulf, thanks for your measurements. If you have time, you could scan your 2*4 mm thick U-340 filter to measure its real transmission (we only have the calculated one) and make a comparison. OD calculations at 8 mm thickness are sensitive to errors if the data was measured at 2.5 mm.

I have already done that, but more like a quick test to see if there were any traces of the IR peak.

I could not detect anything except measurement noise above OD5.

 

The OD is very likely better for the IR - peak and the calculated data for 8mm is not very sensitive if calculated from the 2.5mm base thickness as at 2.5mm there are reliable information for that peak.

You are not seeking an exact OD with many decimals.

 

Please observe that this red graph for 2 x U-340, 4mm is not properly showing the OD from 400nm to 600nm.

 

 

The ZWB1 8mm test above is a composite of several wave bands and averages of up to 6000 measurements to eliminate measurement errors from crosstalk in the spectrometer.

The total measurement and post processing time is several hours.

 

I might eventually do the same for the U-340 stack, but not soon.

[colinbm]

Thanks Ulf

My practical tests show me that the 8mm ZWB1 is an excellent filter for UV A & B lights, LED or CFL sources, to block any visible pollution in fluorescent photography.

Cheers

Col

[Stefano]

Thanks Ulf. Interestingly, the ZWB1 seems to have a lower peak than the U-340.

[ulf]

Thanks Ulf. Interestingly, the ZWB1 seems to have a lower peak than the U-340.

Yes, that is interesting and might be useful in some situations.

It also have a slightly wider peak (75nm - 66nm)

 

Mainly the U-340 seam to be optically more dense. Then there are also losses from two more surface passages.

[Doug A]

Did anyone one else shoot thru the 8mm ZWB1? Were the photos sharp? Tangsinuo now offers this as a standard purchase item.

Thanks,

Doug A

[KhanhDam]

what is the purpose of using an 8mm thick filter vs a more standard 2mm thick one?  Seems like the extra thick glass just makes photos blurry. do the thinner 2mm versions also cause the photos to be blurry?

[Andy Perrin]

9 minutes ago, KhanhDam said:

what is the purpose of using an 8mm thick filter vs a more standard 2mm thick one?  Seems like the extra thick glass just makes photos blurry. do the thinner 2mm versions also cause the photos to be blurry?

The 2mm ones need an IR blocker stacked with them. At 8mm you can dispense with the IR blocker, and then you have less reflection losses. Nobody except me had blur issues! I got a bad piece apparently. 

[ulf]

4 hours ago, Andy Perrin said:

The 2mm ones need an IR blocker stacked with them. At 8mm you can dispense with the IR blocker, and then you have less reflection losses. Nobody except me had blur issues! I got a bad piece apparently. 

That is the reason for the 8mm thickness.

The other reason for this unusually thick filter is that it blocks the upper UV-A wavelengths above 375-380nm.

The usable transmission is for lower UV-A and UV-B.

 

I wanted this filter as a complement to my stack of two U-340, 4mm.

That stack is quite more expensive, but also gives a better IR-blocking at around 700nm.

[LarsHP]

I have just received my 8mm thick ZWB1 filter and have successfully mounted it in the prepared filter + adapter ring stack. It is composed like this, made of generic rings: 

 

1) Empty 52mm filter ring. (The filter groove in such a frame is about 50.5mm while the aperture is about 47mm.)

 

2) 52 to 55mm step up ring. The inside diameter (aperture) is slightly more than 49mm, which makes it a perfect fit.

 

3) 55 to 52mn step down ring plus the retaining ring from the empty 52mn filter ring to tighten the glass disc in the stack. (I recommend mounting the retaining ring in the step down ring before putting it on.) 

 

4) There is plenty room for threading a 52mm hood, if needed. 

 

5) A filter box from Tangsinuo with 52mm filter holder foam, but no bottom foam, works well as container. 

 

 

 

[Ming]

Tangsinuo has a ring to go with this filter.  You could have asked for it when you placed the order.  The ring has no markings, but it will be hard to mistake it for anything else.

 

 

[LarsHP]

13 hours ago, Ming said:

Tangsinuo has a ring to go with this filter.  You could have asked for it when you placed the order.  The ring has no markings, but it will be hard to mistake it for anything else.

 

 

That is a nice looking filter ring for this fat filter. It isn't listed in the Tangsinuo eBay shop, and it's not mentioned here either, so naturally I didn't ask for it when ordering. Quite odd that they don't list it when selling such an odd sized filter. Where did you see it first yourself?

[Ming]

I asked Jason the options to mount the filter.  He said he could offer it with a 52mm ring.  I gladly took his offer.  That's it.

 

[LarsHP]

5 minutes ago, Ming said:

I asked Jason the options to mount the filter.  He said he could offer it with a 52mm ring.  I gladly took his offer.  That's it.

 

Quite understandable, but since I didn't know this option existed, I didn't ask.

Next time, I will ask before ordering: I want 3mm QB21 filters, which isn't listed, but I will suggest to Jason that they make it, instead of ordering two 1.5mm filters.

[ulf]

I was the one originally asking Tangsinuo for a round 8mm thick ZWB1.

Then they did not have such a ring.

Ming mentioning it was the first time I heard of it.

[ulf]

12 hours ago, LarsHP said:

Next time, I will ask before ordering: I want 3mm QB21 filters, which isn't listed, but I will suggest to Jason that they make it, instead of ordering two 1.5mm filters.

A QB21, 3mm sounds interesting. I might want to get one of those too, even if prefect restoration to VIS of my FS-camera have not been that important for me.

Even a 3mm filter round needs a thicker filter ring if you want it to have exposed front filter threads.

I already have a few BG40, 2mm that works acceptably well for restoring to something like the stock camera, beside my BG38, 2mm.

 

In nature I think there are not that many surfaces like the cloth that are black, but highly IR reflective. 

[LarsHP]

4 hours ago, ulf said:

A QB21, 3mm sounds interesting. I might want to get one of those too, even if prefect restoration to VIS of my FS-camera have not been that important for me.

Even a 3mm filter round needs a thicker filter ring if you want it to have exposed front filter threads.

I already have a few BG40, 2mm that works acceptably well for restoring to something like the stock camera, beside my BG38, 2mm.

 

In nature I think there are not that many surfaces like the cloth that are black, but highly IR reflective. 

You are most likely right about that. However, the black cloth test shows that there is IR leakage, so any plant with near IR radiation will have some discoloring, I expect. Whether that is invisible or negligible using a custom camera color profile is another story.

 

EDIT

See my quick test here:

 

[ulf]

I am fully agreeing with you Lars that the IR has some impact and 1.5mm QB21 is definitely way to thin to be enough.

For me the absolute correct visible VIS colour restoration have not felt that important though.

 

Without any practical tests to proof it I guess that 2mm BG40 can be just as good as 3mm QB21
I bought most of my real Schott filter glass from from member Steve's company (Cadmium).

 

Some of what I think is BG40 I bought from this a bit questionable company:

https://www.ebay.com/sch/i.html?item=196099763720&rt=nc&_trksid=p4429486.m3561.l161211&_ssn=image-laboratory

 

The "UG11" and BG-glass I bought from them seams to match the correct transmission for UG11 and BG40. Even some that was supposed to be BG38.
I do not know if the missmatch was due to ignorance or intentional.

 

They have a rather rude way of communicating and do not expect their customers to have a proper way of verify their claims with a proper spectrometer system.

 

[LarsHP]

44 minutes ago, ulf said:

I am fully agreeing with you Lars that the IR has some impact and 1.5mm QB21 is definitely way to thin to be enough.

For me the absolute correct visible VIS colour restoration have not felt that important though.

 

Without any practical tests to proof it I guess that 2mm BG40 can be just as good as 3mm QB21
I bought most of my real Schott filter glass from from member Steve's company (Cadmium).

 

Some of what I think is BG40 I bought from this a bit questionable company:

https://www.ebay.com/sch/i.html?item=196099763720&rt=nc&_trksid=p4429486.m3561.l161211&_ssn=image-laboratory

 

The "UG11" and BG-glass I bought from them seams to match the correct transmission for UG11 and BG40. Even some that was supposed to be BG38.
I do not know if the missmatch was due to ignorance or intentional.

 

They have a rather rude way of communicating and do not expect their customers to have a proper way of verify their claims with a proper spectrometer system.

 

Thanks for the link. I saw that seller on eBay before, but didn't feel confident about it. If I recall correctly, the listing was for some UV pass filter, and in the description they were quite aggressive, and saying nonsense that there are no wide angle lenses that can be used for UV photography. I was tempted to write them about the Kuribayashi / Kyoei 35mm f/3.5 lenses, but naturally didn't. I'd rather buy from friendly and respectful dealers.