scanner "discovery?"

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

Ken:
Very observant of you. Are you sure you don't recall having read about this
technique previously? Because "sweet spot" is exactly the same term commonly
used in scanning that describes relatively noise-free areas of the scanning
platten. The usual technique is to scan a clean piece of white paper and
then enhance the contrast of the scan. Everyone who owns a consumer level
scanner should do this to find the best areas to place scanning material.
Even film scanners (at least every one that I've owned) display the same
fault. Some professional flatbed scanners employ stitch scanning along the
x-y axes to achieve uniform resolution and quality independent of the
placement of the source material on the platten.
Dane

> Accidentally stumbled upon something that may be of
> interest to those of you scanning film and slides for
> archival purposes. Then again, I may simply be
> "re-inventing the wheel". You decide for yourselves
>
> So - the light bulb went off; I decided to scan an
> empty slide slot. Pull up the gain, and I should see
> how much and where the dust was so I could clean at least
> the one slot in the template perfectly.
>
> Tried the second slot (in epson's template) and it was
> much much quieter. Night and day difference, apples and
> oranges. Third one was acceptable, but not quite as clean
> as the second. And the fourth was the same as the first,
> amazingly noisy, but tapering to worst at the bottom.
>
> Clearly this means that the "sweet spot" at least on mine
> is the second slot. Why I have no idea, but promise it's
> so.
>
> Having said all that, scanning the identical transparency
> in both slots one and two, with the gain at normal, I can
> see no apparent difference. But - neat image sure can!!!
>
> I invite comment, and suggest that others experiment
> themselves with their own machines before beginning any
> big projects.
>
> If I'm preaching to the choir, I apologize.
>
> Take care.
>
> Ken
>

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

On Thu, 25 Aug 2005 04:06:18 GMT, Ken Weitzel <kweitzel@shaw.ca>
wrote:

>Here's what's happened. Eyes are getting older, getting
>harder to see dust on the flatbed glass. See it in the
>morning, when the sun glares on it, but then the sun is
>also glaring on the monitor. Evenings can see the monitor
>perfectly, but can't see the dust well.
>
>So - the light bulb went off; I decided to scan an
>empty slide slot. Pull up the gain, and I should see
>how much and where the dust was so I could clean at least
>the one slot in the template perfectly.

That's a well known method of spotting dust and scratches on the
flatbed scanner's glass.

1. Clean the glass thoroughly on both sides. <=!!!
2. Lift the lid and scan "nothing" in a darkened room.
3. Afterwards, brighten up the image in an editor until pale gray.
and then...
4. Shriek it horror! ;o)

Another tip for a quick check I discovered accidentally is to lift the
lid in a darkened room and then start a scan with nothing on the
glass, as above. Next, squat down until your eyes are virtually on the
same height as the glass. As the light sweeps down the length of the
scanner it's very easy to spot all debris and glass damage.

Don.