Re: DIY light source for 10X10" enlarger.

"Thor Lancelot Simon" <tls@[EMAIL PROTECTED]
> wrote in message 
news:ftkgj0$rc7$1@[EMAIL PROTECTED]
> In article 
> <WJadnUplxbSmrmDanZ2dnUVZ_uKpnZ2d@[EMAIL PROTECTED]
>,
> Richard Knoppow <dickburk@[EMAIL PROTECTED]
> wrote:
>>
>>   Cold light lamps are just fluorescent lamps. I think 
>> you
>
> Yes and no -- they've got a somewhat unusual spectrum and 
> they have
> special ballasts and a large preheater.  The latter two 
> differences
> from your run of the mill fluorescent lamp are meant to 
> make them
> more useful for enlarging by reducing the warm up time 
> that causes
> problems for short exposures.
>
> These are worthwhile differences but with an enlarging 
> timer that
> measures light output, like the Metrolux, much less so.
>
> -- 
>  Thor Lancelot Simon 
> tls@[EMAIL PROTECTED]
    Not all cold light heads have the heaters. They are 
mostly on Arista lamphouses and are meant to maintain the 
light output of the lamp when not run continuously. The 
phosphors may be different but there are at least two types 
of lamp offered by Arista, one being balanced better for VC 
paper. One can buy several types of flourescent lamps 
including at least one phosphor with a visual color similar 
to incandescent lamps. The spectral outputs for the 
phosphors are available from most lamp manufactuers so its 
possible to see if the spectra is suitable for VC paper.
    I have no idea of what differences there are in the 
balasts other than to withstand intermittent operation.
    All gaseous discharge lamps have outputs which increase 
with temperature so they like to run hot. In a diy lamphouse 
the only method of getting consitent light output is to run 
the thing continuously and use a shutter to control the 
exposure.


-- 
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]