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UltravioletPhotography

a paper about xenon flashes


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Thanks,Werner.

 

The flash paper is interesting.

 

I am not a big fan of the Ocean Optics USB 2000 spectrometer, but for capture of fast events such array type instruments are about the only solution. They do correctly note that "there is considerable noise in the UV region of the spectrum" the extent of which is perhaps not a concern for this study.

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Has any one found what lens was used in this study? I only found mentioned Nikon D3200 tht had been modified, not a word on the lens. The schematic overview in their Fig. 1 shows a camera that looks like a D3200, plus something eerily reminding of a kit zoom lens. Other illustrations show a lens I cannot immediately verify. Could be a Noflexar?

 

Any way really stange to write a techical paper of this kind and leave out such important information.

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That was exactly my question :-)

 

The text sounds as the lens was just part of the "modified camera".

 

I do not think it is a Noflexar:

 

post-21-0-16450600-1431626652.jpg

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Not the first time technical papers are troubled by obvious omissions.

 

A pity such elementary errors are overlooked by peer reviewers or editors.

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Search of the pdf finds no occurrence of the word "lens", perhaps it is described i better in one of the cited references.

Here is a little better look from the downloaded pdf file.

post-24-0-03195700-1431630763.jpg

If I might hazard a guess it looks like a black variant Nikon 50mm f/1.8 Series E.

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The Nikon Series-E lenses while listed among the Non Dedicated UV-Capable Lenses in UV Sticky #2 do not transmit very deeply do they?
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They are OK for UV but nothing more.

 

However, my remark was directed to the fact that a modern low-end DSLR like the D3200 almost always is matched with similar low-end AF kit zoom lenses. A Nikon 50E will not even meter on the D3200.

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  • 6 months later...

I just now am reading the linked paper. Very interesting.

 

I've never experimented much to record UVIVF using my UV flash - usually choosing to use one of the UV-LEDs. But I know some of our members have done ths.

 

There is extensive discussion of the effects of ambient stray light on fluorescence results. Of necessity in a museum there is sometimes a need to permit some ambient light because an object is really big and cannot be photographed in total darkness.

 

Of great interest to me, was the note that a white balance of 5600K was used for the luminescence work. This correlates with our members' observations that daylight WB worked well (enough) to capture the fluorescent colours reasonably accurately.

 

The difficulties with leaky violet light in UV pass filtration are also noted.

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A summary of filtration from Xenon flash for reflectance and luminescence (multispectral) imaging in cultural heritage applications by Giovanni Verri & David Saunders, The British Museum Technical Research Bulletin, Vol 8 2014.

 

The excitation filtration is not 'perfect' in the first two rows for transmission of Vis or IR but is discussed in the paper. And stronger filtration is used in the last row.

 

Screen Shot 2015-11-24 at 1.52.45 PM.jpg

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Of great interest to me, was the note that a white balance of 5600K was used for the luminescence work. This correlates with our members' observations that daylight WB worked well (enough) to capture the fluorescent colours reasonably accurately.

 

Since with emission source colours you are trying to capture the "true" colour of the source and not balance a scene to correct a source induced colour cast, Daylight balanced film always worked well and subsequently so does Daylight WB for digital.

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I've sometimes had problems in the dark closet setup getting my fluorescent colours correct. Not major problems. Just drifts in one direction or another. "-)
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