Re: point UV light source
awef6t@itchy.mi.net
Tue, 21 Nov 1995 20:53:32 +0300
>>
>> Other than the sun, does anyone know of a point source for ultra violet
>>light?
>> Recently I have seen correspondence saying that Pt/Pd exposed to
>>sunlight made
>> sharper prints than those made under fluorescent tubes, and it was speculated
>> that it could be because the sun is a point source and the tubes are highly
>> diffuse. Perhaps someone here can add something to the discussion.
>>
>> John Dixon
>>
>> E-mail from: John L.Dixon, 21-Nov-1995
>
>I have observed the effect you refer to in my own work. I suspect that
>it has more to do with the lack of perfect contact between negative and
>paper than it does with the nature of the light source,
Ditto in my own experience. I had to work with glass plates up to 14 x 17
in. at one time. The problem became obvious with photographs of suspended
bridges with lots of perfectly sharp lines. With conventional printing
frames it was impossible to obtain perfect shapness everywhere.
Also, I once saw a microfiche diazo duplicator. Since the microfiches have
lots of extremely small text that has to be enlarged considerably to be
read the duplicating equipment has to do a superb job. It did. It used a
vacuum frame and the light source was made of several blacklight
fluorescent tubes. No point-source light there.
Luis Nadeau
awef6t@mi.net (new e-mail address)
Fredericton, New Brunswick, Canada