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UltravioletPhotography

Some unusual UG filters. UK supplier, H V Skan


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I recently found myself looking for a specific filter and while browsing Google, came across a company called HV Skan, based here in the UK.

 

They have a link to their stock, and when I looked through it noticed some UV filters I had not heard of. Link here; https://www.skan.co.uk/images/filter-list.pdf

 

Anyway, after a quick chat with them on the phone, in turns out they have some quite unusual stuff going back many many years, as they do not like to get rid of glass, so have a number items which are no longer made.

 

I bought the following, which I am looking forward to testing.

 

UG2, 50mm diameter, 1mm thick

UG3, 25mm diameter, 1mm thick

UG5, 25mm diameter, 0.5mm thick

UG12, 25mm diameter, 3mm thick

 

These are unmounted, although they can resize and machine filters as needed (they don't do mounts though). Now I just need to handle a 0.5mm thick filter without breaking it....

 

I'll post up transmission spectra for them when I've run them.

 

I have checked and they do not have any KV418 unfortunately. But if there is anything you are specifically after, which isn't listed, it's worth getting in touch with them as they said not everything they have in on there.

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I am so late in acknowledging this post, Jonathan !

But thanks. Their list looks interesting.

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So Ug6 became Ug8. Ug7 was discontinued due to low sales.

What happened to Ug9?

 

People do need to remember that film sensitivity cut off around 650 to 700nm. Quite the opposite as to today. Film was good for UV and horrible for IR.

Now digital is excellent for IR and okish for UV.

 

Looking at even those graphs, its not hard to see why UG11, Ug1 and Ug5 took over. Best of all their targets.

 

Looking back it seems the difference between Ug11 and ug5 was nickel vs barium.

 

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I hope to get some transmission spectra measured for these over the weekend. Be interesting to see how they compare with the book ones. I have actually found a place in Germany that has a block of UG6. The glass itself wasn't too expensive, however the cost they were wanting to charge to have it made into a filter put me off (700euro to make a filter to size).
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Sorry David, I didn't realize those were actual filters in the book.

I will scan those pages and post then.

 

VG6 is not in production, the only two VG filters available right now are VG9 and VG20.

post-87-0-27618300-1584702585.jpg

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OK, lets see if I have the correct,

UG6 changed to UG8, that is in the book.

UG7 was discontinued, and therefore there is no graph in the book for that.

I don't have any idea about the UG9, it is possible there never was a UG9.

 

So the only thing I need to scan is UG8, hold on.

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Pages 23 and 39 have info about UG8. It is more of an IR filter, not a U filter (black glasses, infrared transmitting, page 12/13, line 8).

 

post-87-0-26478100-1584704687.jpg

 

post-87-0-53896000-1584704710.jpg

 

post-87-0-57811100-1584705580.jpg

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Ug8 has nothing to do with UV. Very interesting.

50% at 1000nm!

Thank you Cadmium. This step into history has been really cool.

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Here's the transmission spectra of 3 of the filters I recently got from HV Skan (as measured on my Ocean Optics FX spectrometer);

 

UG2 1mm

UG3 1mm

UG12 3mm

 

post-148-0-59041900-1584794955.jpg

 

EDIT - I originally put up a scan with 4 filters. However Stefano rightly pointed out that the UG5 one looked odd. I checked the spectrometer files, and have also gone back and re-run the scan, and it does not look like UG5 at all, which is very strange. So I have removed it from the graph here until I can find out what it actually is.

 

Now, how can I be certain that these ones are correct. I suppose the answer there is that I cannot be, as they are old filters no longer made. However looking at the Schott online filter calculation programme, the UG3 scan does look to match, so at least that one should be ok.

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That UG5 curve looks odd, it should pass IR much more at that thickness.

 

Also, it doesn't pass violet-blue-green, a thicker version (which should pass even less visible light) is used to make the BUG U filter.

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Stefano, you're right, I'll double check my spreadhseet.

 

EDIT - strange the spreadsheet looks correct. As they say "get a strange result, redo the experiment". I shall redo my set of measurements, and figure out what is going on.

 

EDIT - having now redone the scan, the UG5 0.5mm does not look right, so I have removed it, until I can find out what it is.

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That UG12 looks good. With a S8612 filter I could see that being a good pair.

 

Can you post garden photos with them on their own and with a 2mm S8612 cut filter?

 

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Maybe just me but I find this interesting that stacking U360 up doesn't give you the same advantage as U340(ug11) also the same higher UV transmission for twice the glass.

post-188-0-79182200-1584863404.png

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Interesting stack, using UG5 0.5mm thick compared to UG5 1mm thick.

I agree.

It would be interesting to try one of those thin filters.

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The UG5 0.5mm would have been for a specific job that I wanted to try. Somewhat annoying that that would be the one for which the spectra didn't match what it should be for UG5 0.5mm (or even UG5 of any thickness). I will be following up with them on monday as to what has happened. On the plus point they do have other stocks of UG5, so there is still a chance of getting a thinner one in the correct material.
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Jonathan, Skan mentions "All filter glasses feature treated edges and are thermally toughened.". The thermal treatment might have changed the optical performance a bit?
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Jonathan, Skan mentions "All filter glasses feature treated edges and are thermally toughened.". The thermal treatment might have changed the optical performance a bit?

 

Hi Alaun, I could understand a small change, but the scan for what was supposed to be the UG5 0.5mm was missing the shoulder fro 400nm to 600nm which should have been there. Unfortunately it wasn't a minor difference. I'm sure it's nothing serious, and something they can rectify.

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