Scanning old glass negatives

I am doing a lot of historical documents including old postcards and
glass negatives. Has anyone here done glass negatives? A lot of these
are hand dipped. Some are hand cut and not quite square. So far we have
been making contact prints and scanning them. These things are getting
old (like a hundred years old) and the emulsion is starting to flake
off. Each time they are handled may be their last. One problem with a
flatbed scanner is that it focuses on the surface of the glass and not
on the emulsion which is where the picture is. Is there anyone out
there with the same problems ???


Thanks much, K.

<kirstenh@optonline.net> wrote in message
news:1105972581.146652.251790@c13g2000cwb.googlegroups.com...
>I am doing a lot of historical documents including old postcards and
> glass negatives. Has anyone here done glass negatives? A lot of these
> are hand dipped. Some are hand cut and not quite square. So far we have
> been making contact prints and scanning them. These things are getting
> old (like a hundred years old) and the emulsion is starting to flake
> off. Each time they are handled may be their last. One problem with a
> flatbed scanner is that it focuses on the surface of the glass and not
> on the emulsion which is where the picture is. Is there anyone out
> there with the same problems ???
>
>
> Thanks much, K.
>
What about a light box and a camera to photograph the glass negatives? With
the correct copy stand, you can get a very good copy of the glass negative
without touching the emulsion.

I do not claim to know how the scan glass negatives. Much less hundred year
old ones.

You said that the scanner focuses on the surface of the scanner glass, which
is true for a CIS sensor, but you can put the emulsion side of the glass
negative on the scanner glass, if that does not harm the negative. If the
image is reversed or right to left, you can correct in a photo editor
(Photoshop) or even in some scanners twain interface's.

CIS scanners do focus on the surface, but CCD sensors have plenty of depth
of field to handle the thickness of the glass of a glass negative.

If you are using one of the Canon LiDE series scanners, then that is a
problem. Any of the other scanners, with a CCD sensor should work fine.

--
CSM1
http://www.carlmcmillan.com
--

On Mon, 17 Jan 2005 16:16:30 GMT, "CSM1" <nomoremail@nomail.com>
wrote:

>CIS scanners do focus on the surface, but CCD sensors have plenty of depth
>of field to handle the thickness of the glass of a glass negative.

CCD sensors do have some depth of field but the problem is once you
move the object away from the surface - even a little - you lose
contrast and dynamic range very rapidly (see below).

I would put the glass negative (emulsion down) on the scanner, then
set the scanner to "film" (to turn off the light) and use a diffuse
external light source to illuminate the negative. (I doubt that the
scanner's "film light" in the cover would be enough.)

Another - out of left field - suggestion may be to use a projector and
project the negative focusing to the top of the scanner glass (put a
white sheet of paper to focus, then remove). I haven't actually tried
this, but it should work. Just make sure the projector doesn't shake
as the scanner head moves. As a bonus you would get higher effective
resolution.

OK, back to loss of contrast...

I'm currently wrestling with glossy photos which cause Newton's rings
and sometimes stick to the glass causing gray splotches in the scan.

My solution is to affix the photo to a piece of Plexiglas with
double-sided tape to keep it flat and then use pieces of cardboard
strategically placed around the photo for the Plexiglas to rest on.
That way the whole contraption "floats" just enough above the glass to
avoid Newton's rings and other artifacts. Compared to a regular scan
(photo resting on the glass) there is a noticeable loss of contrast
and dynamic range (e.g. the highlights are darker) but I fix that
later in Photoshop.

Don.

I have done glass negatives ... from the 1940's ... on my Epson Perfection
4870.

The procedure is to place the glass negative emulsion side down on the
scanner's glass bed, and scan exactly like any other negative. Sometimes
careful handling is required, but I have not had any problems with the ones
I have tried. [FWIW: Almost all of them were three-color separations or
three-color "one shot" camera negatives, mostly done on Kodak "Super
Panchro Press Type B" glass plates.

I do *not* think that you will have **any** problems with the emulsion
"flaking off" if it is a standard silver-based emulsion. Unfortunately, I
cannot speak to what kind(s) of problems you might have with older forms of
emulsions ... except that some of them *may* be quite delicate, and you
should probably check with a for-real "Archivist" and learn how to handle
them properly.

I am in the Los Angeles area ... if you have any further questions, you
might try contacting me "off list."








<kirstenh@optonline.net> wrote in message
news:1105972581.146652.251790@c13g2000cwb.googlegroups.com...
> I am doing a lot of historical documents including old postcards and
> glass negatives. Has anyone here done glass negatives? A lot of these
> are hand dipped. Some are hand cut and not quite square. So far we have
> been making contact prints and scanning them. These things are getting
> old (like a hundred years old) and the emulsion is starting to flake
> off. Each time they are handled may be their last. One problem with a
> flatbed scanner is that it focuses on the surface of the glass and not
> on the emulsion which is where the picture is. Is there anyone out
> there with the same problems ???
>
>
> Thanks much, K.
>

In article <41ec32b6.264007@news.individual.net>, Don
<phoney.email@yahoo.com> writes
>
>Another - out of left field - suggestion may be to use a projector and
>project the negative focusing to the top of the scanner glass (put a
>white sheet of paper to focus, then remove). I haven't actually tried
>this, but it should work.
>
There isn't a hope in hell of that working with a conventional scanner,
Don, and a simple ray trace will explain why. Ye canny brek the laws o'
physics - light travels in straight lines.

Only the light that passes through the projector lens *and* the flatbed
glass surface *and* the scanner lens can be focussed onto the CCD to
produce the output. Unless both of those lenses are considerably larger
than the scanner glass surface area then only a very small portion of
the image will be focussed onto the CCD - effectively the convolution of
the scanner and projector lens pupils - and that will be pretty small
indeed.
Glass
Scanner G
Lens G
| G
| G
|/SL------I----------------------------------------Projector
x-SL------I----------------------------------------P Lens
|\SL------I----------------------------------------P
^ G
^ G
^ G
CCD G
G
Glass

Only those rays roughly shown above, passing through the points marked
'I' on the flatbed glass can contribute to the image formed on the CCD.
All of the points on the scanner glass marked G have rays which come
from the projector and completely miss the scanner lens, so cannot form
an image. The lenses are fairly small compared to the flatbed width, so
you don't get a very large image area and what you do get is very
unevenly illuminated with a very bright central spot.

A corollary to this method would be if you place a sheet of white card
on your window and project an image onto that for focussing purposes and
then remove the card. Now walk outside and look at the image you see on
your window - you won't see or photograph the image projected, just an
out of focus image of the illuminated projector lens that varies in
intensity as you move your head across the window, changing the relative
alignment of the projector lens with your eye lens.

Short of redirecting every photon incident on the glass towards the
scanner lens, using a fresnel lens, or keeping the white paper on the
glass as a means of scattering the light so that some of it reaches the
scanner lens (although most will be lost) there is no way to get light
form any reasonable image size onto the CCD.

By contrast, if the scanner were a CIS device then there is a good
chance that this technique would work, because the detector itself
subtends the entire scanner width and no scanner lens is necessary, but
there isn't a hope of it working with a conventional CCD scanner.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

On Tue, 18 Jan 2005 20:33:21 +0000, Kennedy McEwen
<rkm@nospam.demon.co.uk> wrote:

>>Another - out of left field - suggestion may be to use a projector and
>>project the negative focusing to the top of the scanner glass (put a
>>white sheet of paper to focus, then remove). I haven't actually tried
>>this, but it should work.
>>
>There isn't a hope in hell of that working with a conventional scanner,
>Don, and a simple ray trace will explain why. Ye canny brek the laws o'
>physics - light travels in straight lines.

Hence, the "out of left field' moniker... ;o)

>The lenses are fairly small compared to the flatbed width, so
>you don't get a very large image area and what you do get is very
>unevenly illuminated with a very bright central spot.

I see.

>A corollary to this method would be if you place a sheet of white card
>on your window and project an image onto that for focussing purposes and
>then remove the card. Now walk outside and look at the image you see on
>your window - you won't see or photograph the image projected, just an
>out of focus image of the illuminated projector lens that varies in
>intensity as you move your head across the window, changing the relative
>alignment of the projector lens with your eye lens.

That's not exactly the same because there is a distance between the
window pane and the eye. Only if the eye is literally stuck to the
surface of the window pane (or at least the same small distance as
between the scanner lens and the top of the scanner glass) where the
image is focused, would it be the same.

But I take your point. I'm reminded of my 8mm days. A similar effect
may be walking in front of the projection screen, looking at the
projector and expecting to see a clear image. Like you explained
above, the most one may see are image fragments with a bright spot in
the middle.

Followed by stepping on everyone's toes as you try to find your chair
in the dark with severely contracted pupils... ;o)

>Short of redirecting every photon incident on the glass towards the
>scanner lens, using a fresnel lens, or keeping the white paper on the
>glass as a means of scattering the light so that some of it reaches the
>scanner lens (although most will be lost) there is no way to get light
>form any reasonable image size onto the CCD.

I was just about to suggest that! Is there a ("milky") optical glass
with such properties which could be placed on top of the scanner?

But I see your point about most of the light being lost as it seems to
relate to my current struggle:

I'm now wrestling with glossy photos which not only literally stick to
the scanner glass (causing gray "splotches") but also cause Newton's
rings. I "solved" this by affixing the photo to a piece of Plexiglas
with double sided tape to keep it flat and then raising the whole
contraption with strategically placed pieces of cardboard around the
photo to support the Plexiglas. Although the scanner does have enough
depth of field I do notice a quite radical reduction in contrast which
I have to correct for later.

You explanation above (serendipitously) seems to suggest why.
Apparently, having a photo "float" fractions of a mm above the scanner
glass seems to lose a lot of light too. However, after I correct the
image later I don't really see any loss of detail (subjective
estimate). Is there (theoretically and objectively) any loss of detail
by having the photo "float" just above the glass?

>By contrast, if the scanner were a CIS device then there is a good
>chance that this technique would work, because the detector itself
>subtends the entire scanner width and no scanner lens is necessary, but
>there isn't a hope of it working with a conventional CCD scanner.

It would be an interesting CIS test, although as I mentioned last
time, there is still a problem of the scanner and the projector moving
because - unlike an object on the scanner glass - the two are
uncoupled and move independently as the scanner assembly shuttles back
and fort.

Don.

In article <41ee98c1.7897430@news.individual.net>, Don
<phoney.email@yahoo.com> writes
>>A corollary to this method would be if you place a sheet of white card
>>on your window and project an image onto that for focussing purposes and
>>then remove the card. Now walk outside and look at the image you see on
>>your window - you won't see or photograph the image projected, just an
>>out of focus image of the illuminated projector lens that varies in
>>intensity as you move your head across the window, changing the relative
>>alignment of the projector lens with your eye lens.
>
>That's not exactly the same because there is a distance between the
>window pane and the eye.

There is a distance between the scanner lens and glass bed - otherwise
the lens pupil would have to extend the full width of the glass. So it
is just the same situation as described above.
>
>But I take your point. I'm reminded of my 8mm days. A similar effect
>may be walking in front of the projection screen, looking at the
>projector and expecting to see a clear image. Like you explained
>above, the most one may see are image fragments with a bright spot in
>the middle.
>
Exactly - the glass does virtually nothing, excepting some minor
scattering and linear shifts of the non-orthogonal rays, to the light
coming from the projector.

>Is there a ("milky") optical glass
>with such properties which could be placed on top of the scanner?
>
A fine ground glass screen can work, which is effectively all that
Anti-Newton-Ring glass is. Even so, that will only allow some of the
rays from all of the image to be scattered into the lens pupil, but
there will still be light fall off towards the edges, or a "hot spot" in
the middle, just as you get with back projection systems if viewed on
axis. A fine fresnel lens will correct this, if you use the correct
focal length, just as the viewing screen on an SLR camera uses ground
glass for image forming and a fresnel lens for illumination flattening.
In this context though, quite an expensive proposition.

>Apparently, having a photo "float" fractions of a mm above the scanner
>glass seems to lose a lot of light too. However, after I correct the
>image later I don't really see any loss of detail (subjective
>estimate). Is there (theoretically and objectively) any loss of detail
>by having the photo "float" just above the glass?
>
Light loss in your case is because you are increasing the distance from
the light source. For a point source this is an inverse square law, so
double the distance and you quarter the illumination. Being an extended
source, the fall off is less radical, but how much depends on the light
source geometry.

Loss of detail should only be due to defocus and reduced signal to
noise.
>
>It would be an interesting CIS test, although as I mentioned last
>time, there is still a problem of the scanner and the projector moving
>because - unlike an object on the scanner glass - the two are
>uncoupled and move independently as the scanner assembly shuttles back
>and fort.
>
I doubt that this would be significant given the actual exposure times
for each CCD line - but it depends on the size of the projected image.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

On Wed, 19 Jan 2005 18:36:59 +0000, Kennedy McEwen
<rkm@nospam.demon.co.uk> wrote:

>>Is there a ("milky") optical glass
>>with such properties which could be placed on top of the scanner?
>>
>A fine ground glass screen can work, which is effectively all that
>Anti-Newton-Ring glass is. Even so, that will only allow some of the
>rays from all of the image to be scattered into the lens pupil, but
>there will still be light fall off towards the edges, or a "hot spot" in
>the middle, just as you get with back projection systems if viewed on
>axis. A fine fresnel lens will correct this, if you use the correct
>focal length, just as the viewing screen on an SLR camera uses ground
>glass for image forming and a fresnel lens for illumination flattening.
>In this context though, quite an expensive proposition.

What's a fresnel lens? (I meant to ask last time but I forgot.)

>>Apparently, having a photo "float" fractions of a mm above the scanner
>>glass seems to lose a lot of light too. However, after I correct the
>>image later I don't really see any loss of detail (subjective
>>estimate). Is there (theoretically and objectively) any loss of detail
>>by having the photo "float" just above the glass?
>>
>Light loss in your case is because you are increasing the distance from
>the light source. For a point source this is an inverse square law, so
>double the distance and you quarter the illumination. Being an extended
>source, the fall off is less radical, but how much depends on the light
>source geometry.
>
>Loss of detail should only be due to defocus and reduced signal to
>noise.

As I mentioned before, since I have a conventional CCD scanner there
is sufficient depth of field so I don't see any focusing issues.

I was only concerned with loss of detail but, if I understand
correctly, that shouldn't really be a problem. I need to boost
contrast somewhat in postprocessing to "cheer up" the highlights which
are dulled due to the loss of light, but other than that I'm not
really losing anything, am I?

Don.

In article <41efc9d0.7626985@news.individual.net>, Don
<phoney.email@yahoo.com> writes
>On Wed, 19 Jan 2005 18:36:59 +0000, Kennedy McEwen
><rkm@nospam.demon.co.uk> wrote:
>
>What's a fresnel lens? (I meant to ask last time but I forgot.)
>
A thin lens - one which is designed without the normal glass bulk. I am
sure you have seen them as cheap lightweight reading magnifiers etc.

Lens power is a consequence of the surface curvature, which refracts the
light according to Snell's law and the angle of incidence due to that
curvature, and the internal medium has no effect since light continues
to travel in a straight line through it to be refracted again at the
rear surface, which is usually at a different angle. If this was the
same angle as the front surface, then the lens has no power and the
light is refracted back to its original path - which is why you can see
an undistorted image through a flat sheet of glass, or a meniscus lens
at the correct viewing distance.

In a conventional lens the curvature of the surface requires significant
bulk in the lens body because the surface is continuous. However, since
only the curvature is important in the lens function, the surface can be
designed with discontinuities so that the bulk of the lens is
eliminated. If the discontinuities are perfectly perpendicular to the
light path then the Fresnel lens will perform exactly as well as the
conventional lens, but this can only be achieved for one particular
point, usually on the focal plane. At all other points, the
discontinuities in the surface cause scattering and loss of performance.

Some lens designs combine the fresnel approach with conventional lenses
and another of Fresnel's developments, the zone plate, to produce what
are known as binary or diffractive optics, where the discontinuities
occur exactly on the zone plate transitions, so contributing to the lens
performance rather than detracting from it.
>>
>>Loss of detail should only be due to defocus and reduced signal to
>>noise.
>
>As I mentioned before, since I have a conventional CCD scanner there
>is sufficient depth of field so I don't see any focusing issues.
>
Nevertheless, they will be there, however minor they are. There is only
one point of focus, everywhere else is just an approximation.

>I was only concerned with loss of detail but, if I understand
>correctly, that shouldn't really be a problem. I need to boost
>contrast somewhat in postprocessing to "cheer up" the highlights which
>are dulled due to the loss of light, but other than that I'm not
>really losing anything, am I?
>
You will possibly be losing some detail due to defocus and, whilst you
don't notice any, without knowledge of the scanner design it is
impossible to determine whether any loss is significant or not.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Hello, the best kind of scanner for glass negs with peeling emulsions
is the kind with a "film drawer" such as the Microtek 1800f or the old
Agfas. In this arrangement the negative is scanned with the emulsion
up, so the emulsion never is touched. Unfortunately there is newton
ring problems when the glass plate touches the glass bed of the film
drawer, so I have to apply a little tape on each side or corner of the
base side of the plate to act as a spacer to lift the plate slightly up
off the glass.

Top issue for scanning old plates is dmax, which is the range of dark
to light values that a scanner can see through. As far as I know, the
Artixscan 1800f, which is available for about $1,000, has the greatest
depth of any scanner under $10,000, and it is better than the Artixscan
2500 or any of the Epsons. If you have the money, the best scanner for
glass plates is the Creo Eversmart Supreme 2, which is about $28,000.
Used Creos, Fujis, and other high end scanners are occasionally
available used for about $5000, but if you are buying used scanners you
need to excersise extraordinary precaution to protect yourself if the
deal goes bad, and you need to learn how to dismantle and repair the
scanner yourself. Most scanner factories now only offer repair service
for the warranty period, and after that you need to pay to exchange
your old scanner for a new one. Parts and service are unavailable for
Microtek, Epson, etc., after the warranty period. Buyer beware.

If you are scanning old plates, you will be much better off to do it in
16 bit rather than 8 bit mode. Feel free to contact me off-list, i
scan glass plates for a living.
Tom Robinson
http://historicphotoarchive.com