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Date:	Thu, 3 Apr 2014 07:28:21 -0400
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Subject:	Re: [geda-user] printing from PCB
From:	Jason White <whitewaterssoftwareinfo AT gmail DOT com>
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Although I have never seen this before it would seem to be a
transparent ruler with "calibrated" gray scale blocks printed on it.
This would seem to be a way to measure opacity of the masking films
and to make judgments about process variables such as how long should
the PCB be exposed before developing it. If it is used the way i think
it is, ie. lay it down on a sensitized PCB and measure how long it
takes the 8th block to become completely exposed, then it could
actually be quite handy.

http://www.stouffer.net/TransPage.htm

"The Stouffer 21-Step Transparent Guide is heralded around the world
as "the platemaker's choice". It serves as a gauge to evaluate the
variables encountered in the exposure and processing of lithographic
plates and photographic materials by contact. If indicates the
direction and magnitude of exposure or processing adjustments
necessary to achieve the desired results. It is also used with contact
positives, silk screen, printed circuit boards, and most other
photographic applications for judging results, determining speed and
contrast for emulsions, and hardness of coatings."

On Thu, Apr 3, 2014 at 5:04 AM, Richard Bown <richard AT g8jvm DOT com> wrote:
> On Wed, 2 Apr 2014 13:26:34 -0400
> DJ Delorie <dj AT delorie DOT com> wrote:
>
>>
>> If you're doing UV photoetching, here's what I suggest:
>>
>> Export your layers as PNGs at whatever your printer's maximum square
>> physical resolution is.  Postscript leaves too much to the interpreter
>> (for example, ghostscript and HP give different results), the PNG
>> exporter has been hand-tweaked to give exact coverage for just this
>> purpose.  This step can be automated via makefiles or scripts.
>>
>> Figure out how to control your printer better than your printer
>> driver.  I wrote my own software for the Epson series so that I could
>> control drop size and placement myself, to get clean edges without
>> smearing.
>>
>> Print on Jetstar Premium UV film with the highest ink density your
>> printer can handle.  I've tried a lot of films and none do it right
>> except this one.
>>
>> Get a Stouffer 21-step transmission wedge and calibrate your exposure.
>> Most films require a hold at 8.
>
> Hi
> thanks
>
> BTW what is a  Stouffer 21-step transmission wedge  ?
>
> --
> --
> Best wishes /73
> Richard Bown
> Email : richard AT g8jvm DOT com
> HTTP  :  http://www.g8jvm.com
> nil carborundum a illegitemis
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-- 
Jason White

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