[alt-photo] Re : Re: UV Point Light Source

[ding dangdong]

I have been using this setup for a little more than four years now.  My print 
sizes start from 28x40cm up to whole sheets of Fabriano and i have always 
suffered from light falloff especially observable with cyanotype during 
exposure. Quite a pain because im not at all good at techy calculations and 
stuff so had to resort to a lot of trial and error in solving this little 
annoyance. Right now, i have suspended two bulbs with 55cm distance from frame 
and had it enclosed in a DIY folding box of gaffered sheets of insulating 
material (foamcore with aluminum foil on one side much like those folding 
sunscreens for your dashboard). i also have my frame sit on a 'carousel' or sort 
of a lazy Susan, a box with wheels that allows me to rotate the frame under the 
lights to balance the exposure. Kind of dodging and burning from old darkroom 
days. A messy lot of 'systeme D' like they call it here in France that leaves a 
lot of room for improvement but so far its working. My base times for cyanotypes 
are in the 30mins and gums at 5 mins. 
Anybody out there with better suggestion than my rotating frame?

I apologize for mistakes in my english, not my native tongue. So is French even 
if i live here in Paris. 
Ding




________________________________
De : Tomas Sobota <tom at sobota.net>
À : The alternative photographic processes mailing list 
<alt-photo-process-list at lists.altphotolist.org>
Envoyé le : Lun 23 mai 2011, 10h 10min 34s
Objet : [alt-photo] Re: UV Point Light Source

Alberto,

After switching the lamp on, you have to wait a couple of minutes before
using it. After this time (more or less) you see the light change color from
the usual yellow to a greenish hue. That is the visual signal that the lamp
has started emitting UV. This change is quite fast and you notice it easily.

The lamp gets hot, but not extremely since a great part of the 300W
dissipate as non-caloric UV. More than UV tubes, to be sure. But with a
separation of 50cm or so from the print, the heat does not reach it
noticeably. Not even in summer, from my experience.

When you finish the exposure, you have to wait until the lamp cools down
before turning it on again.

Tom

On Mon, May 23, 2011 at 8:24 AM, Alberto Novo <alt.list at albertonovo.it>wrote:

> Philippe Berger wrote:
>
>> I use also a Osram UltraVitalux for my Carbon Transfer. It is perfect, no
>> problem
>>
>
> Isn't it too hot, and the light increasing for the first minute or so after
> the switching on?
> Alberto
> www.grupponamias.com
> www.alternativephotography.com/wp/photographers/rodolfo-namias-group
>
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