Re: Plans for a Cheap Collimated UV Light Source

The only place I ever notice a loss of sharpness when using a black light
bed with the tubes only about one and a half inches from the paper is when
the paper is very rough resulting and the neg is not being pressed into the
valleys of the texture. With good contact (I only use plate glass and a
heavy weight on top to press my paper down) my gums look very sharp and
compare well to those printed in the sun. Many sun printed images lose
sharpness because the print frame will not always have the pressure to
flatten warped heavy paper. Also remember that the whole sky is radiating
UVs and trying to creap in under your neg if contact is not ideal. I do not
yet have a vacuum frame but think that that is the best answer for
sharpness. Use the light source that will give you the exposure time and UV
range you need for your printing and put your effort into getting good
contact. Using digital negs my gum printing time is in the range of 2 to 6
minutes most of the time with the above mentioned UV bank.

> From: bsinger <bsinger@sasktel.net>
> Reply-To: alt-photo-process-l@sask.usask.ca
> Date: Tue, 01 Nov 2005 13:52:07 -0600
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: Plans for a Cheap Collimated UV Light Source
>
> Michael Koch-Schulte wrote:
>
>> This plan appears to offer possible improvements over the eepjon plans for
>> building a UV light source for alt printing, it purports to be more
>> collimated. Probably has longer burn times as the distance from bulb to copy
>> is greater but the offer or greater sharpness may be attractive to those who
>> require it.
>>
>> ~m
>>
>> http://www.thinktink.com/stack/volumes/voliii/equipment/uvlamp/uvlamp.htm
>>
>>
>>
>>
> I am in the process of building a light source to print gums. The idea
> that the light should be collimated seems to make sense, yet as far as I
> can remember, has never been a big deal in any discussion I have read
> about light sources.
>
> Collimated light may be required when you are using UV to burn micro
> processors etc. but is it required for printing gums. After all, the
> simple way these plans develop collimated light is quite eloquent but
> results in a loss of brightness, which I would like to avoid.
>
> It seems to me that the answer may already exist to this question. That
> is.a comparison of image resolution between sunlight and artificial UV
> light sources might be the answer. Because of the great distances
> involved, sun light could be considered collimated. Has any one ever
> studied whether there is a difference between sunlight and the various
> artificial UV light sources in terms of resolution or "sharpness" in gum
> printing.
>
>
Received on Tue Nov 1 15:46:49 2005