Archived posting to the Leica Users Group, 2006/12/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 >>> >>> >>> >>> _______________________________________________ >>> Leica Users Group. >>> See http://leica-users.org/mailman/listinfo/lug for more information >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information