Holding mounted slides firmly in place

[Don]

This is a long shot because I don't think a lot of people worry about
it, but here goes anyway...

Hardware: Slide mount adapter/holder (in my case Nikon)
Media: Mounted slides

I scan all slides twice as a matter of course (don't ask...).
Naturally (?) there is a slight misalignment between the two scans
forcing me to do sub-pixel alignment in post processing.

What I'm looking for is a "method" to minimize this misalignment by
holding the slide in place as firmly as possible.

Things like sandwiching an empty slide holder on top of a slide and
"ramming" them both in so the slide sits more tightly in the scanner
(Nikons tend to rattle a lot). That particular "method" risks the
window on the two slides not aligning perfectly (not to mention
weakening the springs) so I'm looking for any other clever ideas along
those lines.

The key is to hold the slide in place as firmly as possible without
damaging the scanner or using materials which would release clouds of
dust, fumes, etc.

Lateral thinkers, start your engines... ;o)

Don.

 

[Alan Browne]

Don wrote:

Things like sandwiching an empty slide holder on top of a slide and
"ramming" them both in so the slide sits more tightly in the scanner
(Nikons tend to rattle a lot). That particular "method" risks the
window on the two slides not aligning perfectly (not to mention
weakening the springs) so I'm looking for any other clever ideas along
those lines.

- Cut up some rubber bands into strips. Thinner and more compressible.
- Split the blank slide holder in two pieces to thin it out

Why do you do two passes (I'll ask).

Will multipass scanning accomplish what you need?

Will a copy of the digital file of a single scan acheive your needs?

Cheers,
Alan

 

[Allodoxaphobia]

This is a long shot because I don't think a lot of people worry about
it, but here goes anyway...

Hardware: Slide mount adapter/holder (in my case Nikon)
Media: Mounted slides

I scan all slides twice as a matter of course (don't ask...).
Naturally (?) there is a slight misalignment between the two scans
forcing me to do sub-pixel alignment in post processing.

What I'm looking for is a "method" to minimize this misalignment by
holding the slide in place as firmly as possible.

Things like sandwiching an empty slide holder on top of a slide and
"ramming" them both in so the slide sits more tightly in the scanner
(Nikons tend to rattle a lot). That particular "method" risks the
window on the two slides not aligning perfectly (not to mention
weakening the springs) so I'm looking for any other clever ideas along
those lines.

The key is to hold the slide in place as firmly as possible without
damaging the scanner or using materials which would release clouds of
dust, fumes, etc.

Lateral thinkers, start your engines... ;o)

Don.

I wouldn't be surprized to find that your "offset problem" is _not_
due to the movement of the slide -- but, rather the not-exactly-
reproducible-re-positioning of the scanner's mechanics.
I'm sure you've already done your damnedest to lock down the slide.
For any one scan, any scanner (for loose definitions of "any") is
probably rock-solid in its "geometry".
But, for any two separate scan operations, the "guts" may start
off e v e r s o s l i g h t l y different than it did on the
previous scan.

Jonesy

 

[Ian Buckner]

This is a long shot because I don't think a lot of people worry about
it, but here goes anyway...

Hardware: Slide mount adapter/holder (in my case Nikon)
Media: Mounted slides

I scan all slides twice as a matter of course (don't ask...).
Naturally (?) there is a slight misalignment between the two scans
forcing me to do sub-pixel alignment in post processing.

What I'm looking for is a "method" to minimize this misalignment by
holding the slide in place as firmly as possible.

Things like sandwiching an empty slide holder on top of a slide and
"ramming" them both in so the slide sits more tightly in the scanner
(Nikons tend to rattle a lot). That particular "method" risks the
window on the two slides not aligning perfectly (not to mention
weakening the springs) so I'm looking for any other clever ideas along
those lines.

The key is to hold the slide in place as firmly as possible without
damaging the scanner or using materials which would release clouds of
dust, fumes, etc.

Lateral thinkers, start your engines... ;o)

Don.

The "trick" to accurately repeatable positioning is not to
"hold...as firmly as possible", but to make sure the position
is not over-constrained.

The classic example for 2 dimensions is the 3-legged stool
versus the 4-legged. The 3-legged one always sits flat on the
floor, while the 4-legged one will rock unless the legs are
extremely accurate, or the stool can flex - it is over constrained.

I have not looked at the location mechanism in my CS 5, if you
are that concerned you should consider doing so before doing
something rash. An issue is that the slides you are positioning
are not very rigid, any more than quite light forces will distort
them in possibly unforeseen ways and amounts.

I recall from many years ago a friend doing research on making
diffraction gratings. That requires orders of magnitude more
precision than you are interested in. The "clamps" he was
using were spring clips with around the same force as the CS 5
applies to a slide.

Look up "kinematic mount".

Regards
Ian

 

[Don]

- Cut up some rubber bands into strips. Thinner and more compressible.

Wouldn't it be hard to slide the frame in with a rubber band strip on
top? Also, I risk the rubber band strip moving and obstructing the
image, or worse dropping into the scanner.

Maybe I don't understand what you mean?

- Split the blank slide holder in two pieces to thin it out

I'm now playing with a variation on this theme. The slides in question
are cardboard mounted Kodachromes. Since cardboard mounts appear
considerably thinner than (most) plastic ones I can get away with
sandwiching two. On the empty one I enlarged the window by cutting
thin stripes so it does not obscure the image in case of a slight
misalignment.

Why do you do two passes (I'll ask).

To extend the dynamic range of my scanner. Kodachromes in particular
are very dense. I find that the 14-bit of dynamic range my scanner has
(LS-50) is just not enough. It should be, in theory, but it isn't. So
I "contrast mask" - actually a variation on the theme - and for that I
need perfect alignment.

Will multipass scanning accomplish what you need?

Only up to a point. I ran some tests and it just doesn't reveal the
amount of detail in shadows a second scan with a 2-3 ev boost does.

However, multiscanning is somewhat moot because my scanner can't do
single-pass multiscanning. And with multi-pass multiscanning I'm back
to square one - alignment.

Will a copy of the digital file of a single scan acheive your needs?

No, because the second scan has a different exposure.

Don.

 

[Don]

I wouldn't be surprized to find that your "offset problem" is _not_
due to the movement of the slide -- but, rather the not-exactly-
reproducible-re-positioning of the scanner's mechanics.
I'm sure you've already done your damnedest to lock down the slide.
For any one scan, any scanner (for loose definitions of "any") is
probably rock-solid in its "geometry".
But, for any two separate scan operations, the "guts" may start
off e v e r s o s l i g h t l y different than it did on the
previous scan.

Yes, I realize that. At this level of accuracy (4000 dpi in my case)
scanner mechanics are bound to cause some misalignment and I have no
control over that.

However, I would like to try and limit any misalignment I do have
control over.

In the end, I will probably have to continue to sub-pixel align most
scans.

Don.

 

[Don]

The "trick" to accurately repeatable positioning is not to
"hold...as firmly as possible", but to make sure the position
is not over-constrained.

The classic example for 2 dimensions is the 3-legged stool
versus the 4-legged. The 3-legged one always sits flat on the
floor, while the 4-legged one will rock unless the legs are
extremely accurate, or the stool can flex - it is over constrained.

The lock mechanism in my Nikon is basically two plastic rods relying
on their elasticity to hold the slide frame in place. They are quite
smooth - as they should be to allow the frame to be inserted and
retrieved - but this may limit how firmly they hold the frame in
place.

I have not looked at the location mechanism in my CS 5, if you
are that concerned you should consider doing so before doing
something rash. An issue is that the slides you are positioning
are not very rigid, any more than quite light forces will distort
them in possibly unforeseen ways and amounts.

I have considered that too i.e. making sure that whatever I do the
slides remain fully horizontal and are not distorted in any way.
However, these (old) Kodachrome slides are quite warped (the film, not
the frame). So much so that any distortion due to forcing them more
firmly in place will be insignificant by comparison.

Some of these slides "sag" considerably in the middle causing serious
focusing issues with the narrow depth of field Nikons. But I'm not up
to ripping up the cardboard slides and using anti-Newton mounts
because that would open up another slew of problems - potential damage
to film, clouds of dust and debris, time consuming, etc.

Look up "kinematic mount".

Will do! Thanks!

Don.

 

[DavidTT]

You probably are well aware of this already. Gepe and Wess both make
thicker plastic slide mounts. Some models work well for me for these
reasons:

- full frame, without round corners and border fuzz from paper mounts
- holds the film flatter than paper mounts

If interested, I'll look up the model numbers.

 

[Mendel Leisk]

I scan all slides twice as a matter of course (don't ask...).

snip

Can't resist, why scan twice?

Would a single scan saving a Vuescan raw file do?

 

[Bart van der Wolf]

(e-mail address removed) (Don) wrote in message


snip

Can't resist, why scan twice?

Would a single scan saving a Vuescan raw file do?

Careful, we don't want another non-productive VueScan (or any other
program) bashing rant ;-)

The main reason for anyone needing to combine two scans at different
(shadow+highlight) exposure levels, is when the scanner has a limited
dynamic range. That poses a problem, mainly with slides which have a
higher density range to span, than most negatives do.

If the exposure is properly maximized without clipping the most
transparent image parts, a lower dynamic range scanner will have
reduced dense image area quality. One way of boosting quality is by
averaging multiple exposures, which will reduce random noise caused by
the scanner electronics, and by photon shot noise which is most
noticeable at low signal levels (dense image areas).
Another way is by combining two (linear gamma) exposures at different
levels (a long and a short exposure), which extends the density range
that can be handled.

The problem with a longer than optimal exposure (to better penetrate
the dense film areas) is potential blooming from the transparent film
areas, the spilling over to adjacent sensors of excess electrons
(especially noticeable near high contrast edges). So that requires
clever blending and masking, which is further complicated by the need
to keep the two exposures in perfect registration to avoid blur.

VueScan's "long exposure pass" attempts to automate the exposure and
blending steps, but doesn't address the registration step. It could be
addressed if the scanner could be instructed to do two different
exposures with a stationary scan head assembly, but I think there may
be firmware restrictions that prohibit *changing* the exposure time
while a scan pass is being made. Even if it were possible, there will
still be blooming issues which can be more or less prominent depending
on scanner model.

Bart

 

[Don]

On Wed, 06 Oct 2004 13:26:32 GMT, (e-mail address removed) wrote:

Thanks David. The problem is I would then have to rip up the cardboard
mounts and I'm weary of that because of inadvertent damage to film,
clouds of dust and debris, time consuming... etc.

On the plus side, as you write, I would then get the full frame,
reduce focusing problems and eliminate round corners and "the fuzz"
but - very reluctantly - I decided to push on scanning with paper
mounts.

Not a perfect solution by any means, but it appears (to me at least)
to be the lesser of two evils. Still, not happy about it, but have no
choice... :-( Eventually, I came to my senses and had my slides
developed unmounted.

Anyway, as for the original problem, sandwiching a second, empty,
paper mount with an enlarged window seems to improve things! There are
still slight misalignments due to inherent scanner mechanics but at
least I have a feeling I've done everything I can to keep the slides
in place.

Don.

 

[Don]

snip

Can't resist, why scan twice?

Because even my 14-bit scanner unfortunately just doesn't have enough
dynamic range to penetrate those dense Kodachromes. After, literally,
months of agonizing and countless tests (as well as the purchase of a
new scanner - I used to have a 10-bit scanner before that) the only
consistent and streamlined workflow seems to be to scan twice, once
for highlights (the usual AutoExposure scan, but with highlights
clipping at 0) and a second scan with, usually, a +3.0 ev boost to get
the data out of the shadows.

Would a single scan saving a Vuescan raw file do?

The problem is a single scan doesn't reproduce the full dynamic range
(the root of the problem). I now scan "raw" with NikonScan albeit with
2.2 gamma (and ICE where possible).

Not to mention I wouldn't touch VueScan with a 10-foot pole... (fx:
runs for cover) ;o)

Don.

 

[Don]

Careful, we don't want another non-productive VueScan (or any other
program) bashing rant ;-)

Well now... that's coming from someone who's forced to use Minolta
software because VueScan is so buggy... ;o)

Seriously though...

The problem with a longer than optimal exposure (to better penetrate
the dense film areas) is potential blooming from the transparent film
areas, the spilling over to adjacent sensors of excess electrons
(especially noticeable near high contrast edges). So that requires
clever blending and masking, which is further complicated by the need
to keep the two exposures in perfect registration to avoid blur.

And the two need to be "color coordinated"! That's the biggest
problem!!! The color balance changes with exposure so the two scans
are "out of sync" color-wise. None of the contrast masking approaches
I know of, such Gaussian blur, blending modes (Photoshop), etc address
this.

Due to this color imbalance it's impossible to use these methods on
images where the border between the highlights and shadow scans falls
in the middle of a gradient - which is a sizeable chunk, if not the
majority, of all images! The result is a noticeable color imbalance
even with the targeted blurring of the transition area.

I don't find blooming to be a problem because the shadows I try to get
at are quite "far away" from areas which bloom. Specifically (given
2.2 gamma) the areas of the AutoExposure (i.e. the highlights) scan
I'm cleaning up with the boosted (shadows) scan are in the 0-32 range.
Blooming usually happens way on the other side of the histogram and
never reaches that far into the shadows. Unlike traditional contrast
masking methods where both images are combined in full, I only combine
areas of relevance, so blooming areas and deep shadow areas are both
excluded from the composite image, to be replaced with the properly
exposed areas from the other scan.

VueScan's "long exposure pass" attempts to automate the exposure and
blending steps, but doesn't address the registration step.

That's just one of the major problems, the other being color
imbalance.

Because of all that VueScan's "long exposure pass" is not really
useful. It ends up just being a time-consuming way to create a blurred
image.

It could be
addressed if the scanner could be instructed to do two different
exposures with a stationary scan head assembly, but I think there may
be firmware restrictions that prohibit *changing* the exposure time
while a scan pass is being made.

That's just one of the many ideas in the back of my mind I would
*love* to try and tackle but - no time... :-(

Don.

 

[Bart van der Wolf]

On Thu, 7 Oct 2004 12:36:52 +0200, "Bart van der Wolf"
So that requires clever blending and masking, which is further
complicated by the need to keep the two exposures in perfect
registration to avoid blur.

And the two need to be "color coordinated"! That's the biggest
problem!!! The color balance changes with exposure so the two
scans are "out of sync" color-wise. None of the contrast masking
approaches I know of, such Gaussian blur, blending modes
(Photoshop), etc address this.

Actually, you 'just' need to adjust the "exposure" of the shadow
exposure file, after recording it as a Raw or linear gamma image.
For example:
- Exposure 1 is for the highlights, maximum non-clipped exposure.
- Exposure 2 is for the shadows, say 4x the exposure of Exposure 1.
Now you need to reduce! the presumed linear gamma luminance levels, by
dividing the luminances by 4! This will provide a seamless fit with
the luminance range of exposure 1, if blended in registration. It will
give a linear 16-bit exposure range with superior photon shot noise
characteristics, and 16-bits will cover a density range of 4.8, well
in excess of what slide film can offer.

Instead of a factor of 4, an exposure factor of 8 can be used, but
that increases the chance of blooming, a bit depending on the scanner.

Bart

 

[Hecate]

On Wed, 06 Oct 2004 13:26:32 GMT, (e-mail address removed) wrote:

Thanks David. The problem is I would then have to rip up the cardboard
mounts and I'm weary of that because of inadvertent damage to film,
clouds of dust and debris, time consuming... etc.

I usually find a craft knife with a good edge, followed by pulling
apart at the corners does the job nicely. Knife must be sharp to avoid
the perils of loose fibres. Follow that with a careful blow fro an air
can and then mount using Gepe full size mounts, the only ones I use
now.

 

[Don]

I usually find a craft knife with a good edge, followed by pulling
apart at the corners does the job nicely. Knife must be sharp to avoid
the perils of loose fibres. Follow that with a careful blow fro an air
can and then mount using Gepe full size mounts, the only ones I use
now.

Thanks Hecate! I do use a snap-off blade for finicky stuff like that
but I'm really paranoid about dust. Really, really, paranoid... I use
a blow brush, a microfiber cloth and I vacuum every day before I turn
the scanner on but when the sun shines through the window there are
still hordes of bad tempered dust particles loitering around like
piranhas just waiting to swarm where I want them the least!

I read once that most dust particles are actually human skin flakes
which is odd because I only shed my skin twice a year... ;o)

Don.

 

[Don]

Actually, you 'just' need to adjust the "exposure" of the shadow
exposure file, after recording it as a Raw or linear gamma image.
For example:
- Exposure 1 is for the highlights, maximum non-clipped exposure.
- Exposure 2 is for the shadows, say 4x the exposure of Exposure 1.
Now you need to reduce! the presumed linear gamma luminance levels, by
dividing the luminances by 4! This will provide a seamless fit with
the luminance range of exposure 1, if blended in registration. It will
give a linear 16-bit exposure range with superior photon shot noise
characteristics, and 16-bits will cover a density range of 4.8, well
in excess of what slide film can offer.

Instead of a factor of 4, an exposure factor of 8 can be used, but
that increases the chance of blooming, a bit depending on the scanner.

That's what I thought and had a long discussion with Kennedy about it,
but it just doesn't work.

I ran numerous tests with the above method even using the following
formula (I work with 2.2 gamma):

output = input / 2^(EV/gamma).

where output is the desired "darkened" scan value while input is the
data from the shadows (boosted) scan. I wrote a program to generate
Photoshop AMP curves for most commonly used exposures (in 0.1 ev
increments from 0.0 to 5.0).

The problem is that Kodachrome is not linear in this respect:

http://www.kodak.com/global/en/professional/support/techPubs/e55/f002_0486ac.gif

so the exposure directly affects the color balance, i.e. the ratio
between different RGB components. While the AMP curves (actually
"lines") do "darken" the scan correctly, this color imbalance is still
evident. Plainly speaking the adjusted image is still "too cyan". Not
so evident if there is only up to about 1.0 ev difference but for the
values I use (3.0) there is a noticeable transition.

Since I don't have the above data sheet for every batch of Kodachrome
I shot, nor do I have the time to work out the exact values for each
exposure, I just use a much faster empirical method which compensates
automatically and that gives me acceptable color match so I don't have
to blur the transition areas.

Don.

 

[RSD99]

You might try something like the "Ionic Breeze" ...
http://www.sharperimage.com/us/en/catalog/productview.jhtml?
sku=SI737SNX&hppos=27

 

[Hecate]

Thanks Hecate! I do use a snap-off blade for finicky stuff like that
but I'm really paranoid about dust. Really, really, paranoid... I use
a blow brush, a microfiber cloth and I vacuum every day before I turn
the scanner on but when the sun shines through the window there are
still hordes of bad tempered dust particles loitering around like
piranhas just waiting to swarm where I want them the least!

I read once that most dust particles are actually human skin flakes
which is odd because I only shed my skin twice a year... ;o)

LOL! Honestly, the Gepe mounts are fantastic. As soon as I've mounted
them they go in sleeves inside covers and the only time they see the
light of day after that is when they go in the scanner.

 

[DavidTT]

Thanks Hecate! I do use a snap-off blade for finicky stuff like that
but I'm really paranoid about dust. Really, really, paranoid... I use
a blow brush, a microfiber cloth and I vacuum every day before I turn
the scanner on but when the sun shines through the window there are
still hordes of bad tempered dust particles loitering around like
piranhas just waiting to swarm where I want them the least!

I read once that most dust particles are actually human skin flakes
which is odd because I only shed my skin twice a year... ;o)

Don.

Having done my share of damage unmounting paper mounts, I know how you
feel. But some of my compositions are so tight that I have to unmount to
expose the 10% image area covered by the mount. Then I found a device
that helps a great deal: Paper Mount Opener, item QM5050, from BCA in
NY, 631-667-8470. This plastic gizmo has a snug channel that lets you
push a slide mount through, while a mounted blade cuts one side of the
mount open without touching the film. Costs a few bucks, and beats the
heck out of using a free hand blade. BTW, BCA took over Wess' products
when the latter went belly up. The Wess full frame mount with pegs to
hold the film flat is AHX500K.

Dust is entirely a different story. I wear gloves when handling film,
and sometimes even take a shower first. <g>