[Leica] Re: Problem with M6 scratching film

["Michael D. Turner" <mike@lcl-imaging.com>]

B. D. Colen wrote:

> uAt 02:00 PM 4/8/99 +0200, you wrote:
> >This is one of the most interesting threads on this list.  But is the
> >problem with the camera or the scanner?  I would assume that *every* camera
> >pressure plate or winding mechanism leaves its stamp on a roll of film,
> >albeit microscopically, much like a rifle barrel carves its mark on a bullet
> >or a typewriter key uniquely strikes a page.  In fact, I would guess that
> >the FBI Crime Lab could identify the camera a roll of film came from if they
> >had to.
> >
> >But if nothing can see the scratches except a scanner, then maybe they're
> >scanning in too much "noise."   There should be a "Dolby" scratch filter for
> >these things.
> >
>
> Now that everyone keeps mentioning it...I to am seeing faint horizontal
> scan marks on scanned negatives - I NEVER observed this problem on any lab
> produced prints....Could it be that this is an artifact of scanning
> technology, which is to say:
>

I have run into this problem a lot with CCD film scanners. Very faint scratches
on the base side of negatives or slides which never show up on prints often show
up very readily on scans. So, yes, it is an artifact of CCD scanning technology.
A real pain. Similarly, grain in black and white negs is grossly over emphasized
with CCD scanners.

>
> The pressure plates on the Ms - and perhaps most other cameras - have
> always produces faint scratches on the film, but simply projecting enlarger
> light through the neg doesn't show them up. When scanning, however, the
> resolution is such that these scratches show up....

Light scattering when enlarging, especially with a diffused light source helps
minimizes the problem, but, when scratches are deep enough to be a problem, an
easy solution is to rub a little "nose grease" into the scratch. Has worked well
for the last century. If you try this when scanning with a CCD scanner, you will
end up with a smeary mess in the general area of application. The only real
solution is to use take the lines out with your favorite image manipulation
software.



Mike