[Leica] Flowers in Ultra-Violet

[len-1 at comcast.net (Leonard Taupier)]

Peter,

Thanks for your comments and interest. Let me try to answer some of  
your questions with my limited knowledge of the subject of ultra-violet.

I have not looked into the response curves of the Nikon digital  
cameras I use. I can only comment on the results I've gotten with  
different cameras.
The D2X has good UV response, much better than the D1H I use for IR.  
The D1H gives very noisy photos.
The D1X has much better IR response than the D2X.
The D200 has no sensitivity to either UV or IR.

That brings us to the frequency spectrum of light from UV through  
visible light to IR.
The Ultra-violet light we are concerned with in photography has a  
wavelength from about 200nm to 400nm (nano-meters)
Visible light is from about 400-450nm for violet to about 600-750nm  
for red. Photographic lenses are designed to pass visible light from  
450 to about 800nm (into the IR zone).

Nikon made a UV 105mm Micro lens for the F series some years ago. The  
lens was made of fluorite glass and had a response between 200nm to  
900nm. This lens is still being produced today (not by Nikon), but is  
too expensive for the casual user. That brings us to the next best  
available lenses for UV. That is the enlarging lens which has a  
response down to about 350nm. My guess then is that the area where  
the photos were taken were between 350nm and 500nm which includes the  
purple area of visible light.

I did, by mistake, take photos without the filter but using the black  
light. The photo became much lighter (same exposure as with the  
filter) but now other colors entered the picture. The dark room  
background became blue and the center of the flower had little yellow  
growths which came out yellow. The main petals were still a light  
shade of violet. This tells me that the black light has visible light  
components up into the yellow area which has a wavelength of about  
580nm.

I have tried other lights called black light bulbs but found they  
were only painted incandescent bulbs with nearly no UV content. What  
really produces UV is the ionization of Mercury vapor, like a  
florescent light tube. I looked into getting Mercury vapor bulbs but  
they are expensive, require a special fixture, and are too dangerous  
to be exposed to.

I hope this answers some of your questions and is not too much  
information.

Regards,
Len


On Dec 17, 2006, at 7:58 AM, Peter Dzwig wrote:

> Leonard,
>
> Wow! Very, very interesting, and very creative too. None of that IR  
> stuff ;-. You must be near the limit of the camera's response. I  
> guess that the D200 just doesn't have the response in that part of  
> the spectrum.
>
> Have you looked at the response curves for the camera?
>
> Any idea where in the UV the picture was taken?
>
> What happens if you don't use the filter? Dies the extra light make  
> much difference?
>
> Peter Dzwig
>
> Leonard Taupier wrote:
>
>> The flowers were exposed with Ultra-Violet light from a black  
>> light  in an otherwise totally dark room.
>> <http://gallery.leica-users.org/v/LeonardT/UV/UV_1.jpg.html>
>> <http://gallery.leica-users.org/v/LeonardT/UV/UV_2.jpg.html>
>> Please comment on what you think.
>> The camera was a D2X at 20 sec exposure
>> Lens an El-Nikkor 105mm f5.6  at f11 mounted in a Nikon PB4  
>> bellows  with a homemade F to LTM adapter
>> Focus was in incandescent light.
>> Exposure black light only, using a hot mirror filter and a B+H 403  
>> UV  bandpass filter.
>> No attempt was made to color correct. The 403 filter is a nearly   
>> black, red filter.
>> I tried the same setup using a D200 and even with a 6 stop  
>> exposure  increase no image was produced.  Totally black.
>> As a retired engineer I can't stop experimenting. I just think  
>> it's  fun. Hope you enjoy it.
>> Len
>> _______________________________________________
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>
>
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