Re: UV-exposure units/ UV LEDs:diagrams

Hi:

I do a lot of alt process work. I contact print with a bank of UV flourescent
lamps 3 inches above my printing frame. My exposure time for cyanotypes is
around 5 minutes.

If you were to use an enlarger the time may be far too long to be practical
and the UV light may damage the negative.

I don't want to discourage people from trying this, but I think the exposure
time will likely be in the range of hours - an hour is only between three and
four stops longer exposure than my contact print time.

To get an idea of exposure someone should compare the exposure time they need
for a contact print to that of an enlargement. How many stops longer is an
enlargement compared to a contact print..

A stop is doubling the exposure time. The difference between 5 seconds and 40
seconds is 3 stops more exposure. 3 stops more exposure than 5 minutes is 40
minutes.

A quicker method may be to make enlarge negatives or enlarged reversal
negatives

see http://unblinkingeye.com/Articles/NbyR/nbyr.html

Gord Holtslander

On Saturday 04 November 2006 5:13 pm, earlj@comcast.net wrote:
> The idea of using an enlarger for alt process work is very intriguing, and
> I think that it just might work. The first question that pops into my mind,
> though, is how the heck do you focus the enlarger? Won't the focus be
> different at 395 nm than at the wavelength of your 'normal' incandescent or
> fluorescent light source?
>
> Earl Johnson
> Inver Grove Heights, MN
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Received on Mon Nov 6 07:08:32 2006