U of S | Mailing List Archive | alt-photo-process-l | RE: UV light box construction

RE: UV light box construction

I built a light box last year for 12x20 which has been working fine. I
couldn't find any explanation of why the distance between the tubes should
be X and why the distance to the neg should Y so I set up a spreadsheet to
calculate the light level at various points across the film plane in order
to find X and Y such that the variation in light level was insignificant. I
ended up with x=6cm and y=18cm which gives a theoretical 13% difference in
light intensity centre to edge.

Of course the calculations are based on assumptions which are not correct -
such as infinitely long tubes and zero reflectance from the sides. I think
the results of the calculations err on the conservative side and you could
probably increase X and reduce Y by some considerable amount before any
variation became 'material'.

I'd be happy to send the spreadsheet (Excel) should you wish to see it - and
anyone else on the list.

Practical advice - paint the inside white. Also I built my box upside down I
think - the box sits face up with the tubes near the floor and the printing
frame goes on neg facing down. I don't think that has any material impact on

Geoff Chaplin
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-----Original Message-----
From: Ken Sinclair [mailto:photo1@telusplanet.net] 
Sent: 22 February 2009 03:15
To: alt-photo-process-l@usask.ca
Subject: UV light box construction

Hi all...

I am now in possession of a sheet of baltic birch, 12 BL tubes,  
ballasts and
the correct number of 'tombstones' and am almost at what one might call
the 'final, too-late-to-change design' stage.

I plan on having the lamps on one 'surface' of the birch 'plate' and  
the ballasts on
the upper.  I have planned to have this "rack" sitting on a 1 inch  
support around
the interior of the box to facilitate easy access when (and if) any  
of the parts need

Before I commit the sheet of plywood to the table saw, I have to  
believe that some
users may have found there to be an optimum distance between the  
lamps, along
with the distance from the lamps to the top of the print frame.

Practical advice would be very much appreciated.


Quando omni flunkus moritati (Red Green's Possum Lodge)