Direct UV light expose on Negative for Kallitype Printing

[lkkang]

hi all,

I just started on Kallitype Printing.

Have shot lots of 4x5 and 5x7 sheets...
Currently , planning to get them printed on transparency paper for contact prints ( Kallitype ).

Question :
is it possible to modify the enlarger light to UV light , mount the negative onto the enlarger , and then directly expose the image onto the sheet of coated paper ?


many thanks in advance..
Billy

[rcmartins]

From what little I know, and just my two cents, it is possible, but very far from practical. The first hardship to overcome is to find a powerful enough UV light source to fit the enlarger head. This could be probably achieved with UV LEDs. The second adversity comes from the lens. As far as I know most enlarger lens block UV light. I have heard rumors of some Nikkor lenses that have a wider bandwidth allowing UV light to go through will less attenuation, but I cannot confirm nor reference. All of these hardships imply that even after having managed to put UV light inside the enlargers head, you would have to wait for several hours, if not days, for a proper exposure. Not quite practical.
What I guess is typically done is to build a small plate with UV lamps that is put directly overhead the sensitised paper - probbly what you are going to do with transparency paper. Instead of transparency paper I would advise to experiment with positive film. I have started experimenting with it and consider very promising.

[Jim Noel]

If you want to make a kallitype by projection you will need a lens which passes UV. There has been a lot of experimentation in this area and some lensehave been produced. These lenses are made of quartz and cost in the $10K-20K range if I remember correctly.

[lkkang]

thanks for the valuable information.. will do more research on this topic..
cool


From what little I know, and just my two cents, it is possible, but very far from practical. The first hardship to overcome is to find a powerful enough UV light source to fit the enlarger head. This could be probably achieved with UV LEDs. The second adversity comes from the lens. As far as I know most enlarger lens block UV light. I have heard rumors of some Nikkor lenses that have a wider bandwidth allowing UV light to go through will less attenuation, but I cannot confirm nor reference. All of these hardships imply that even after having managed to put UV light inside the enlargers head, you would have to wait for several hours, if not days, for a proper exposure. Not quite practical.
What I guess is typically done is to build a small plate with UV lamps that is put directly overhead the sensitised paper - probbly what you are going to do with transparency paper. Instead of transparency paper I would advise to experiment with positive film. I have started experimenting with it and consider very promising.

[lkkang]

$10k~$20k !!!!!


if you want to make a kallitype by projection you will need a lens which passes uv. There has been a lot of experimentation in this area and some lensehave been produced. These lenses are made of quartz and cost in the $10k-20k range if i remember correctly.

[lkkang]

sharing some information here..

We want UVA.... and the range should be as stated : 400-320nm

UV-A : With wavelength 400-320 nm is less intense than UV-B, but is more penetrating and can reach and damage easily the retina
UV-B : Wavelength 320-286 burns the skin and damages the cornea and ocular lenses. It is associated with cataracts
UV-C : filtered off by ozone layer

seems like normal enlarging lens ( Rodagon ) should be good to start with.
http://photographyoftheinvisibleworld.blogspot.sg/2011/01/uv-rodagon-lenses-for-uv.html

picture here.
http://www.pbase.com/kds315/image/131986523/original.jpg

worth a try ?

[lkkang]

similar thread here.
http://www.apug.org/forums/forum43/98340-uv-enlarger.html

[Nathan Potter]

Maybe this is possible using conventional film with a mercury arc source using the 365 nm line with some 405 and 430 nm.

A 500 or 1000 W mercury bulb would need to be placed in an air cooled housing (not trivial) and with a mirror condenser. Heat absorbing glass would be needed between the lamp and the film but the glass would also need to pass the UV. The exposure dose to the film would be a multiple of the dose used for a contact print (4X for a 4X enlargement of 4X5 to 16X20 size print. The right kind of heat absorbing glass might save the film. I'm not sure what dose is required in mw.sec. (joules) for a 365/405/430 mercury source.

I think you could focus the image because I've done that using lithography tools and using proper eye protection (imperative). Certainly focus can be done IIRC using a fluorescent focus aid as suggested by someone on another forum.

Selection of a lens is a headache. You can't stand too much glass absorption because that will increase the burn time on the negative. I think normal enlarging lenses are too absorbing but I'm not sure of that. Find a nice site on this by Klaus Schmidt who is expert on the use of UV photography. Klaus comments here occasionally. For low UV attenuation people use quartz optics or mirror optics neither of which is inexpensive especially to cover the 4X5 format. Perhaps you could stand a 25 to 75% loss of intensity through the lens.

For projection printing you gain around 50% in resolution from the lens just due to the shorter wavelength employed.

It would be an interesting but expensive project but I think it is technically feasible.

Nate Potter, Austin TX.