Those ZWB filters again.....

[Andrea B.]

You get what you pay for in some instances. So don't waste your money on ZWB until the Chinese filter-glass making industry cleans up their act. There is no reason they cannot pour better glass, so I why don't they just do that??

 

Also remember that they are all dual bandpass.

 

Tests show that you can successfully block the IR in these ZWB dual bandpass filters, as we can do with all our Schott and Hoya dual bandpass filters. But it it that pesky Visible leakage that is the problem. Along with random instances of waviness, striations and pitting. (Remember tiny bubbles in filter or lens glass is not a problem.)

 

What is the deal with Optima ZWB glass?

Optima's own data charts (not the graphs, but rather the charts above the graph) show excessive leakage in the Visible waveband.

 

24 Aug 2021: The following link has been removed because the test I made was unfair. I compared the ZWB1 to the wrong U filters.

ZWB1 (1.5mm): Testing for UV Transmission, Visible Leak...

 

Transmission of ZWB1 (2mm), ZWB3 (1.5mm) and BG39 (2.5mm)

Jonathan's charts do not show a Visible leak in the filters, but they may not have fine enough granularity along the y-axis? I need to check with Jonathan about this.

 

Post about ZBW filters: http://www.ultraviol...dpost__p__19538

 

There are other reviews tucked into other posts. If I can dig them out, then I will post additional links.

 

^{EDIT: Corrected spelling of filter name.}

[JMC]

Transmission of ZWB1 (2mm), ZWB3 (1.5mm) and BG39 (2.5mm)

Jonathan's charts do not show a Visible leak in the filters, but they may not have fine enough granularity along the y-axis? I need to check with Jonathan about this.

 

The work I did on the ZWB filters was in the early days of playing around with the Spectrometer I used to have access to. Unfortunately it was so early, that I hadn't realised it had a degree of 'wandering baseline' syndrome. After calibration the baseline would drop to about -0.2% transmission, and I never managed to figure out why. However it was realiably unreliable, in that it would always go abck to about -0.2% across the board, so it may still provide some insight. Here's the original graph, full scale.

 

Here's the same graph zoomed into the baseline.

 

Obviously the ZWB3 lets in visible light across the board, but the 1, is less clear. As the region between 400nm to 650nm is not flat on the graph (there is a definite wobble in there above the noise), I would say some parts of the visible spectra are getting through, up to a max of about 0.03% transmission. Above 650nm it rises quickly, so there will be red contamination getting through. To be honest the graphs aren't ideal, but they are all I have for these unfortunately.

[Andrea B.]

Thanks, man!! Appreciate the update. Your graphs may not be perfect, but they add to the weight of accumulating evidence.

 

I'll say once again: the makers of ZWB filter glass could easily clean up their formulas and glass pours so that they produced quality filter glass at a low cost. But until they do, I cannot recommend ZWB glass. I actually worry about the use of filter glass like this in scientific experiments by those who might not realize that there can be problems.

[JMC]

I've dragged my ZBW1 and 3 filters out from the bottom of my camera bag and run them again on my little Ocean Optics spectrometer for transmission. Mine are called ZWB so apologies, I use ZWB and ZBW interchangeably. The ZWB1 is 2mm thick, and the ZBW3 1.5mm thick. This was run at 500us integration time and 10,000 scans for a total of 5 seconds per scan. I ran baseline, ZWB1, ZWB3, baseline, ZWB1, ZWB3, baseline, and then averaged the respective scans to try and minimise the drift these little solid state devices are so apt to do. Firstly 0-100% transmission;

 

 

Nothing hugely surprising with the 0-100% scan. Now, down to 0-1%;

 

 

Now we see the ZBW3 doesn't even get close to the baseline in the visible region (nice spike at 550nm - cosmic ray event ;) ). The ZBW1 also has quite a shoulder from 400nm to about 440nm. Now even further down, at 0-0.1% transmission;

 

 

Obviously no sign of the ZBW3 here, as it transmits much more than this. Starting to see some issues with baseline drift now, but even so the ZBW1 looks to be letting some light through at about the 0.01-0.02% level across the visible region from 450nm up to 650nm, with significantly more getting through from 400nm to 450nm.

 

Ulf, it'll be interesting to see what yours looks like.

[Andrea B.]

oh la! Looks like I have done a BW/WB reversal again. You would think I'm dysxelic!!

I will fix.

************

 

Thank you for the transmission charts. It seems these filters are not consistent across the various manufacturers -- which is very disappointing. I myself haved not wanted to purchase any more for further (practical) testing at this time because I just don't see the point.