I'll show you my Baader, if you show me yours.

[dabateman]

Actually good to know. I now remember that mine came in a paper box and not a plastic one.

Funny how they don't mark different lot numbers. As these are clearly all different, but all marked the same 245891.

Version or a lot number would have prevented a post like this. I wonder now how much does the IR blockin andd transmission differ between them.

Do all the UG11 substrate thickness feel the same? Maybe hard to tell as the holding rings have changed.

But I wonder if they are all 1mm thick or different.

[JMC]

Bit of an update to this one.

 

I bought my first Baader U about 4 years ago  (I will call this 'Old' for now) and recently I bought a new one as a spare (I will call this 'New'). Outwardly the packaging looks the same (only minor difference, the foam inside the old one is slightly different to the new one. Both filter rings say 'Baader U-Filter 2" (CWL 350nm) #2458291' and are about 5mm deep. Both filters look basically the same to the eye. Old box on the left, new one on the right;

 

I measured the transmission and reflection spectra from them (Ocean Insight FX and STS-IR spectrometers, transmission and reflection done at 90 degrees to the surface). This is where the differences become apparent. First the transmission in the UV;

 

The new one has a much deeper transmission into the UV than the old one. Ignore the tail on the short wavelength side, that is mainly due to stray light in the spectrometer. However the small bump at 305nm on the new filter does seem to be a real feature and not a stray light effect. Overall transmission is also slightly higher on the new one (although mine is 4 years old now and had plenty of use so I can't rule that wear and tear out as a factor). I did however go back and check the transmission spectra for the old one and the low wavelength cutoff hasn't changed over time.

 

Ok, the other end - IR. I measured each filter 3 times here and took an average for each one.

 

I can measure down to OD4 (0.01% transmission), but it all gets a bit noisy down there. I'll split out the scans, and show the 3 runs for each filter now. First the old filter;

 

The old filter does show variability around the 0% transmission line, but no obvious features. Now the new filter;

 

The new filter shows two small bumps, one around 730nm, and the other around 910nm. I think these can be seen on the scans Ulf made as well. So it does look as though my 'old' filter has better blocking in the IR than my 'new' one, but that the new one is still around OD4 in the IR. What surprises me is how good the blocking on my old one was.

 

Now the reflection spectra. I'll show these for the 'red' side for the new and old filters, and the 'green/gold' side, to allow easier comparison. The red side of the two filters;

 

And the green/gold side;

 

Note the reflection spectra are combined from three different wavelength regions - up to 440nm, 440nm to 650nm and above 650nm - and done with two different spectrometers, two different high reflectance standards (mirrors). Hence there are discontinuities in the graphs at 440nm and 650nm. There are some big differences in the reflection spectra of the coatings for the 'new' and 'old' filters. Interestingly the new filter coatings have lower reflectance in the 320-330nm region, which probably explains the better transmission seen there. The dips in the reflection spectrum for the green/gold side do coincide with the 735nm and 910nm transmission peaks, so could be a factor in what was being seen there. However that is just speculation as there are a lot of peaks and dips in the reflection spectra.

 

So the new one has a slight IR leak compared to my old one, and slightly different UV transmission. Does this impact image colour balance?

 

Set of comparison images. Rayfact UV lens (f11). ISO400. 2s exposure time. Hazy sunshine, about 9:30AM (stress test, relatively low UV). 4 different images;

Old Baader U

New Baader U

Old Baader U + 1mm Schott s8612

New Baader U + 1mm Schott s8612

 

I included some s8612 in the test, to try and block IR while having as little impact as I could on the UV.

 

Images collected as RAW files, whitebalanced (with a PTFE target taken with the relevant filter setup). All exposures the same. Images cropped, and autocontrast done (no auto colour). Buttercup as the subject - note there was a slight breeze in the garden, hence a bit of movement in the images.

 

Old Baader U

 

New Baader U

 

Old Baader U plus 1mm s8612

 

New Baader U plus 1mm s8612.

 

The old and new Baader U filters are giving essentially the same images in terms of appearance after white balancing. I also did some analysis on the red, green and blue channels of the PTFE image, and there does not look to be any significant IR contribution to the image when looking at the with and without s8612 images. And remember this was a stress test with relatively low levels of UV.

 

Note, before the auto contrast, the 'new' filter images were obviously lighter than the 'old' ones, which is as would be expected given the greater overall UV transmission.

 

I'm not really seeing much evidence of the improved UV reach here, but that is not a huge surprise - the sensor is most sensitive to the long wavelength end, and there is more UV there too. As such the improved transmission at the short wavelength end would not be expected to obvious.

 

Summary

The new Baader U has improved UV reach compared to one bought about 4 years ago. The reflection spectra of the coatings are also different. It does look as thought current Baader U filters (as of early 2022) still offer sufficient blocking for UV work in sunlight, despite showing some evidence for IR leakage at around the OD4 level. However the lack of differentiating features on packaging makes it hard to be 100% certain what you have got just by casual observation. Not everyone has spectrometers, so something like a test in combination with R72 might work here to see whether there is IR leakage, although without having a know sample to compare against it may be hard to interpret it.

 

EDIT - Just to add, I have fed the transmission and reflection results back to Baader, to see if they have any comment.

[colinbm]

Great work Jonathan
So you don't know what you have until you test it ?

[JMC]

30 minutes ago, colinbm said:

Great work Jonathan
So you don't know what you have until you test it ?

Thanks Colin. It looks as though there are gradual changes to the product, resulting in small variations in the absolute transmission (and blocking). Anyone getting one would be wise to check it by combining it with a Hoya R72 or something similar just in case there are major issues. Over the years I have had similar experiences with many filters, especially dichroic ones, and would recommend anyone using filters to do some of their own tests to check they are as specified. While this is easier (no, not easier, perhaps more straightforward is a better term) with a spectrometer, testing in combination with other filters is more accessible to everyone.

[colinbm]

Thanks again Jonathan
I will have to check mine.
I wonder how you can know when you order a new one that you are getting this wider band one, how would the retail seller know ?

 

[JMC]

1 hour ago, colinbm said:

Thanks again Jonathan
I will have to check mine.
I wonder how you can know when you order a new one that you are getting this wider band one, how would the retail seller know ?

 

I'm not sure they would know Colin. The part number on the box is the same on both, so unless they have the ability to request actual data from Baader on that filter going out (or at least filters from the batch that is currently being sold) then it is unlikely that they would know any more than we do. The graph on the Baader site looks to be an old old one anyway, and well out of date, as that one has IR leakage which you can see on the graph, peaking at around 800nm.

 

My guess is that Baader continually try and improve the filter, and it is this which has lead to the wider bandwidth. They will have tolerances on things like out of band blocking, and as long as it doesn't break those, then if there is an improvement in the main characteristic (the UV transmission) that becomes the next upgrade.

[colinbm]

Thanks Jonathan
All very interesting & I will be watching how this pans out.

[Shane]

I was going to suggest this might be of interest to you

http://nikongear.com/smf/index.php?topic=16423.0

 

however the link no longer seems functional, even by replacing nikongear with fotozones. If anyone can get it to function, please let me know (Andrea, Birna... have any suggestions?). 

[Andrea B.]

Was that link from the old Nikongear which became Fotozones?

 

The new Nikongear is https://www.nikongear.net/revival

[JCDowdy]

Shane,

Is this what you were looking for: https://www.fotozones.com/live/index.php?/topic/39572-baader-u2-over-the-years/

[Shane]

38 minutes ago, Andrea B. said:

Was that link from the old Nikongear which became Fotozones?

 

The new Nikongear is https://www.nikongear.net/revival

Yes

[Shane]

36 minutes ago, JCDowdy said:

Shane,

Is this what you were looking for: https://www.fotozones.com/live/index.php?/topic/39572-baader-u2-over-the-years/

No.... it was about some experiments I suggested to Bob which showed the effects (or lack of) IR leakage on the Baader in daylight.

 It was titled [UV] The Rig and the Light Setup

[JCDowdy]

Here you go: https://www.fotozones.com/live/index.php?/topic/16175-uv-the-rig-and-the-light-setup/

[Shane]

17 minutes ago, JCDowdy said:

Here you go: https://www.fotozones.com/live/index.php?/topic/16175-uv-the-rig-and-the-light-setup/

Thanks John. How did you perform your search to find this posting, through Fotozones (my membership appears no longer valid)?

 

[JCDowdy]

I initially searched "Baader U" and limited the results to topic titles.  When you supplied the topic title I simply searched "The Rig and the Light Setup".

If you are not a Fotozones member your search privileges are likely restricted.

[Shane]

7 minutes ago, JCDowdy said:

I initially searched "Baader U" and limited the results to topic titles.  When you supplied the topic title I simply searched "The Rig and the Light Setup".

If you are not a Fotozones member your search privileges are likely restricted.

Thanks John. I was a lifetime member but login fails and I don't have time to deal with it right now.

 

[JCDowdy]

Well that is to bad you could not get the search to work, there is still some good old UV stuff to mine over there.  I recall that at one time the UV interest group had their own section but that was later moved into a more general area of the site.  Your old link was most likely broken in that move.

[msubees]

Long time no post. I found that I have one like it too:

 

but it says "Baader U-Filter 2"  (HWB=325-369nm) optically polished #2458291.

 

at one time I took it apart (trying to fit another lens ring?) but now I do not have the top ring to fix the filter inside....Mine is green on once side a pinkish another side.

 

at least it did not have any fungus growing on it. I have 3 other glass filters in the same drawer but all have haze or fungus colony like structures... tried 75% alcohol and it did not work.