Archived posting to the Leica Users Group, 2006/12/17

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Subject: [Leica] Flowers in Ultra-Violet
From: len-1 at comcast.net (Leonard Taupier)
Date: Sun Dec 17 16:16:35 2006
References: <7D42FCC1-561F-4CA3-B82E-FD1729356E6B@comcast.net> <45853EE3.4060103@summaventures.com> <60FECAA2-FDD5-4AB1-A53B-DECD7C16648B@comcast.net> <4585CB74.6050102@summaventures.com>

Peter,

You are probably right on the narrow filter. If you look at the  
photos you see a very narrow range of color. I looked at the Luminous- 
Landscape page but only saw the curves for the Canon 20d. My browser  
works fine. I use Safari on my Mac. I may try a wider spectrum filter  
for more interesting results. Not too many available at a reasonable  
price though.

Len


On Dec 17, 2006, at 5:57 PM, Peter Dzwig wrote:

> Leonard,
>
> Having just done a bit of research on the B+W 403, it passes UVA in  
> the range 320-385nm. Given what you said about the enlarging lens  
> having a capability down to about 350nm. That seems to imply that  
> the light that you used is probably predominantly in the region 320  
> - 340nm or so (presumming that the response of the enlarging lens  
> drops off as it approaches the upper limit).
>
> As the 403 is designed as a bandpass filter those cutoffs must be  
> pretty abrupt. Seems that you've concocted a filter with a bandpass  
> of about 20nm!
>
> Interestingly B+W say that the filter factor is VERY sensitive to  
> the emulsion and to the illumination with a factor of BETWEEN 8 and  
> 20. That is probably enough to explain the varying responses for  
> the various sensors in the cameras.
> The D2X presumably has a colour gamut wide enough to reach that far  
> into the IR
>
> To get a look at the gamut curves and so on for a few cameras  
> including the D200,
>
> lok at
>
> http://www.luminous-landscape.com/tutorials/prophoto-rgb.shtml
>
> but you'll need to open it in somrething other than Netscape to get  
> the interactive effects.
>
> Whatever the details, the photos make intriguing viewing. Keep them  
> coming!
>
> Peter Dzwig
>
> Leonard Taupier wrote:
>> 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
>>>> _______________________________________________
>>>> Leica Users Group.
>>>> See http://leica-users.org/mailman/listinfo/lug for more  
>>>> information
>>>
>>>
>>>
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>
>
> _______________________________________________
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In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] Flowers in Ultra-Violet)
Message from pdzwig at summaventures.com (Peter Dzwig) ([Leica] Flowers in Ultra-Violet)
Message from len-1 at comcast.net (Leonard Taupier) ([Leica] Flowers in Ultra-Violet)
Message from pdzwig at summaventures.com (Peter Dzwig) ([Leica] Flowers in Ultra-Violet)