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UltravioletPhotography

Unmodified cameras for UV - a very scientific approach :)


Timber

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One correction. The transmission drops off between 290 and 300 nm, not below 310 as I mentioned before. In any case, it does not make any difference in practice, but I apologize for original mistake.

 

I have two issues with uncoated spectrosil.

 

1) Uncoated. Do I have to say more?

 

2) Spectrosil I once purchased from UK-based optical glass seller had a lot of microscratches out of the packaging, and was extremely sensitive to cleaning (can be scratched with special lens cleaning paper). N-BK7 is much cheaper and stronger. Using it will make no difference in real life photography.

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I'm hardly advocating for the use of Spectrosil. It is simply what I was told was in my camera. And as said above, this is a pretty academic discussion for those of us who don't own lenses that go that low!

 

I guess if I end up with scratches then I'll know it was really Spectrosil, Cadmium. ;)

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I know, and I am not meaning to say anything bad about Spectrosil, just that it would seem given what Alex says that there is no point at all in using it over some other kinds of glass,

such as the BK7, which is probably what most places use.

Alex, is it true then than all cameras have a cover glass and use pretty much the same kind of glass for that? Like for example my Nikon DSLRs?

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OK, confused it with fused quartz. In any case, I never had problems cleaning sensor cover glass for several full-spectrum cameras that I had. Spectrosil got scratched the moment I unpacked it.
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Could you have gotten stung by one of these people who substitute inferior knockoff products for the brand name version? Cadmium and I have been PMing about knockoff filter glass for the past few days.
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Andy, I give you total credit for the BG39 + R72 stack test, showing that the "BG39" glass you have is in fact not BG39. Thus my mention of truth in marketing.

I don't have any experience with Spectrosil, but I think Alex does.

I am fairly sure all the cameras I have had converted are probably BK7, I have cleaned them many times.

There is also Schott glass, but I think most use BK7.

There are several things at work, the sensor limit, the lens limit, the replacement glass, and like Alex says the cover glass limit.

Given all that... and given that Alex has a UV-Nikkor now, I suppose he is best knowing about what the limits are.

I don't have a UV-Nikkor, I am limited to about 320nm.

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But are fused silica and Spectrosil exactly the same?

 

Hi Alex,

It is my understanding that Spectrosil is a type of very high high quality chemically pure fused silica. The link you posted to UQG optics has a link to the datasheet noting the low levels of trace elements. I have ESR/EPR tubes made of Spectrosil which have nothing to do with UV optical properties unless you are also shining a beam of UV into the ESR chamber. B)

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None of this makes much sense. If anything, the hardness numbers for fused silica/Spectrosil are higher than for BK-7.

 

Cadmium, we are talking about scratch resistance. I believe him about the pass bands.

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I am not going to argue about hardness numbers. All I say that the spectrosil that I had in my hands was much more prone to scratches than the sensor cover glass (not BK-7). Remember, that sensor cover glass is also most likely AR coated.

 

Added: BK-7 I also handled before and had no complains.

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Ok, well, if more people come forward with bad stories about Spectrosil, I will worry about it, but for now I will just keep it in the back of my mind. And perhaps for my next camera I will avoid Spectrosil just in case.
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None of this makes much sense. If anything, the hardness numbers for fused silica/Spectrosil are higher than for BK-7.

 

Cadmium, we are talking about scratch resistance. I believe him about the pass bands.

 

We were also talking about transmission of the cover glass, which was what I was intrigued by.

Sorry if I sound like I was debating you, not at all, I was just adding my general thoughts to the discussion.

I just find the limit of the cover glass very interesting.

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