UV filter for a Fuji IS-Pro (Nikon 200 without a UV-IR blocking filter)

[Vincenzo101]

Hi all , I have the camera in object, and I could buy a filter on eBay, for taking pictures in the UV realm; the seller have two kind of filters, the first "This filter made of optically bonded UG11 + BG40 glass", the second "UG11 + BG39 glass"; the seller answered me, saying that "Combination with bg39 has lower IR transmission while combination with BG40 more of it along with more transmission in UV".
What UV filter should you buy, to make images in the Ultraviolet realm? Thanks.

[Bjørn Rørslett]

As elaborated elsewhere, it is the transmittance ratio UV/IR that is significant, not the UV transmission per se (within limits, of course).

The Fuji IS probably has a limited UV response thus getting the best filter is very important. Ask the seller about the UV/IR ratio or failing that information, select the BG-39 stack.

[Vincenzo101]

Many thanks Bjørn...

[Boffin Test NGMember]

For a filter stack to be useful in UV it must suppress the IR leakage to at least OD3.5 - OD4. The thickness of each filter plays a role in that.

Note:  OD4 implies a very low IR transmittance of only .01%.

Given that the Fuji IS-Pro records UV primarily in the 370-400nm region, I would recommend a filter stack which has a peak within that region for faster exposures.

Many of the inexpensive UV-pass filters sold on Ebay are not really made from Schott or Hoya glass. They are made from Chinese ZBW glass which usually has a visible leakage in addition to significant IR transmission. The BG blockers will not block the visible leak, only some of the IR leak.

The best IR blocker to use over a true UG11 filter is made from a blue-green glass named Schott S8612. https://www.ebay.com/itm/Schott-S8612-52mm-x-2mm-UV-IR-Cut-Filter-Visual-Bandpass-IR-Suppression/292317056638?hash=item440f744e7e:g:FhEAAOxyrP9RbQDr

http://www.ultravioletphotography.com/content/index.php/topic/2081-links-to-filters-sticky-and-filters-article/

Neither Bjørn nor I are affiliated with any filter manufacturer.

[Vincenzo101]

As elaborated elsewhere, it is the transmittance ratio UV/IR that is significant, not the UV transmission per se (within limits, of course).

The Fuji IS probably has a limited UV response thus getting the best filter is very important. Ask the seller about the UV/IR ratio or failing that information, select the BG-39 stack.

The link I can give: eBay item 191832155399 . There is a diagram for the "optically bonded UG11 + BG40".

Is this good?

Other filters from the same seller:

191832156223 130 USD

I was unable to find his filter with BG39 filter ...

Thanks.

[Dr Klaus Schmitt]

Yes, it is useful, I have it here and tested it, the version with BG40. Has just a relatively low peak transmittance of about 40%. With BG39 it would be even lower! My "work horse" UV transmission filter, the Baader-U has about 80% peak (1 stop difference).

I think both listings are about the same filter, the more expensive one is just a later listing this seller made ...

[benveniste]

Hi all , I have the camera in object, and I could buy a filter on eBay, for taking pictures in the UV realm; the seller have two kind of filters, the first "This filter made of optically bonded UG11 + BG40 glass", the second "UG11 + BG39 glass"; the seller answered me, saying that "Combination with bg39 has lower IR transmission while combination with BG40 more of it along with more transmission in UV".  What UV filter should you buy, to make images in the Ultraviolet realm? Thanks.

Here's a table of Schott Transmission curves.  The seller's description is correct, but given how little IR light the UG11 passes, I'd probably go with the BG40 version.