Other than cleaning mirrors & lenses anyone any ideas on how to bring the
exposure level up to get black on light grey rather than black on almost
equally dark black background.
Anyone tried translucent thin but very white plastic sheet of some sort
overlaying the original. ?
Reducing the exposure masking increases the exposure but whites out the fine
details.
The paper has gone very brown from air bourne SO2/SO3 , neutralising the
paper with alkali improves things but tends to lighten the black image so no
further forward as far as contrast.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

On Tue, 21 Mar 2006 14:06:54 -0000, "n cook"
wrote:

Other than cleaning mirrors & lenses anyone any ideas on how to bring the
exposure level up to get black on light grey rather than black on almost
equally dark black background.
Anyone tried translucent thin but very white plastic sheet of some sort
overlaying the original. ?
Reducing the exposure masking increases the exposure but whites out the fine
details.
The paper has gone very brown from air bourne SO2/SO3 , neutralising the
paper with alkali improves things but tends to lighten the black image so no
further forward as far as contrast.

One way would be, to scan them into your PC and apply some kind
of color filtering.
May take some effort to get the right filter settings, but in the
end you get 'as new' printouts :-)

--
Kind regards,
Gerard Bok

n cook wrote:
Other than cleaning mirrors & lenses anyone any ideas on how to bring the
exposure level up to get black on light grey rather than black on almost
equally dark black background.
Anyone tried translucent thin but very white plastic sheet of some sort
overlaying the original. ?
Reducing the exposure masking increases the exposure but whites out the fine
details.
The paper has gone very brown from air bourne SO2/SO3 , neutralising the
paper with alkali improves things but tends to lighten the black image so no
further forward as far as contrast.

Hi...

Please do yourself a favour and don't even think about cleaning
mirrors and lenses...

You haven't mentioned the scanner maker or model, but I suspect
what you're looking to do is scan them in either your choice of
either black and white or grayscale. Suspicion is that you'll
find grayscale more to your liking, but experiment yourself to
decide.

You mention wanting to bring the exposure level up; not exactly sure
what it is you mean, but what you really want to "play around with"
is the gamma.

Here's how I'd do it: Find the whitest white (note that white *doesn't*
mean white, but rather an absense of colour. Set that to 100%
Next find the blackest black (again, not black but dark with an
absense of colour). Set that to 0%. Next move the gamma to
your eyes pleasure, making the mid-tone grays look good.

Take care.

Ken

Let me tell you photographer's trick in handling discolored prints (which is
akin
to your problem) and that is rephotographing with a brown or yellow
filter over the lens.(and shooting in B&W)
In your case, you won't reshoot the image, but by resetting the luminance
point to nuetral, in this case some shade of brown, you effectively have
redefined the image as brown and white.
If you consider the brown as white, the black falls into place.
I would experiment by playing with a software filter to compensate for brown
either subtractively or additively, or try adjusting same for the
complimentary
color.
I'm assuming you have software capable of this either as your scanner
package, or perhaps some version of Photoshop.

Hello, les!
You wrote on Tue, 21 Mar 2006 16:23:25 -0600:

I think the OP was talking about a common or garden laser photocopier
probably A3, with a machine like that, your options are very limited and I
would recommend trying the last posters idea with a camera with a decent mp
count and filters, the scanner has potential, but an A4 scanner would make
it very hard work stitching the parts together. Of course it depends on the
physical size of the schematics but with a camera, that's not as much of an
issue. either way, to get decent results is going to take some effort.
Still, I'm sure that when you have recovered the schematics in some decent
electronic form you will make them available to all your friends here on
sci.electronics.repair, - wont you? :^)
Pete

lWith best regards, 3T39. E-mail: