Problem scanning very dark Kodachrome

  • Thread starter Thread starter Dan
  • Start date Start date
SNIP
I don't understand at all why this should be necessary to scan dark
slides. Could you please explain in detail?
Click to expand...

The particular combination of Kodachrome dyes and LED spectral emission of
Don's Nikon scanner result in too low a signal for some channels. In that
case it could be a benefit to be able and adjust individual channel
exposure.

Bart
 
|

....snip|

| I tried combinations of DEE and Analog Gain and Scan enhancer (can't
| remember its precise label -- I'm not at my computer now). I've been
| scanning using the Twain plug-in directly into Photoshop. In the
| preview window, the Natural tab shows a very dark image, the Processed
| image is the one I copied to show how the preview looks, which,
| considering the density of this slide, is pretty good. I'll keep
| trying and let you know the solution, if I can find one.
|
| Dan

Do you have the same results (ie, "preview" doesn't match "processed") if
you forego Photoshop and use NikonScan to edit the scan?

Jean
 
Hello, Don
you wrote...


I don't understand at all why this should be necessary to scan dark
slides. Could you please explain in detail?
Click to expand...

Oh, sorry... The threads move along quickly...

The original question was about Kodachromes. As we all know they are
notoriously difficult on all Nikons, but particularly so on my measly
LS-30 which doesn't even have a Kodachrome mode. The nominal scan is
very dark and has a heavy blue cast. Of course, looking at the slide
with the naked eye, it looks just fine, it's neither dark nor blue.

But I end up with a very badly skewed histogram. A massive cut in red
and an equal boost in blue. And I mean massive! It's not unusual to
have red badly clipped at the black end but only reaching up to around
110, while blue is hovering around 200.

So, if I just boost master Analog Gain that won't do much for my
already meager dynamic range, in particular red. Setting the neutral
point only creates an ugly image full of artifacts, from pixelisation
to banding, reminiscent of a false color image not a continuous tone
photograph.

The only way to recover sufficient dynamic range for a meaningful edit
is by adjusting individual Analog Gain values (boost red, cut blue).
Together with contrast masking (when needed) I manage to get
surprisingly good results - but it takes a lot of work. And it's all
totally impossible without the ability to adjust individual Analog
Gain values.

Don.
 
Dan said:
I have tried unsuccessfully for days to get a decent scan from some
very dark Kodachrome slides from 1978.
Click to expand...

I have some very dark Kodachrome from 1955, that I scanned very
successfully using VueScan and a Nikon 4000ED.

I set Vuescan up to scan manually, and let it autoexpose the first
slide. Then I did successive scans at 0.5x, 2x, 4x, 8x, and 16x the
VueScan "autoexpose" time. This gave me 6 images, and I loaded them
into Photoshop. There was a little color correction necessary on each
layer to get it to match the colors of the other layers and each layer
needed to be moved a pixel or two to align with others. I put a
correction layer (or two) over the top to correct all the colors. (I
find a "curves" layer best, as it gives me the most control.) I had to
guess at some of the colors because I didn't really know what it
"should" look like.

Then I combined the layers using a combination of masks. I may have put
curve corrections over each layer too to help combine the layers
seamlessly, I can't remember.

All the layers were scanned as 8-bit tiffs and combined in Photoshop 7
on an older iMac, and it worked great. In the end result, I got a
wonderful portrait of my mother shot by my father, a few years before I
was born.

If I was doing it today, I'd consider scanning it in 16bit and maybe
stepping the scans by 3x or 4x and using Photoshop CS. There were areas
of my slide that only showed detail when scanned at 16x the "optimum"
exposure.

Does this help?

A
 
Hello, Don
you wrote...
So, if I just boost master Analog Gain that won't do much for my
already meager dynamic range, in particular red. Setting the neutral
point only creates an ugly image full of artifacts, from pixelisation
to banding, reminiscent of a false color image not a continuous tone
photograph.
Click to expand...

I never had these problems with the few Kodachromes I scanned on my
LS40. But I would think that using advanced workflow together with long
exposure pass should solve the problem in vuescan. Did you ever try?
 
Hello, Bart van der Wolf
you wrote...
The particular combination of Kodachrome dyes and LED spectral emission of
Don's Nikon scanner result in too low a signal for some channels. In that
case it could be a benefit to be able and adjust individual channel
exposure.
Click to expand...

If this is the case for Kodachrome generally, I don't see why Ed does
not use differently balanced RGB exposure values as he does for color
negatives (in order to compensate orang mask)...
 
Erik Krause said:
I never had these problems with the few Kodachromes I scanned on my
LS40. But I would think that using advanced workflow together with long
exposure pass should solve the problem in vuescan. Did you ever try?
Click to expand...

I have had a problem with greeen spots showing older slides (of the
US-sponsored overthrow of Presideant Allende-ca. 1972?) that I scanned
with a Nikon 4000 ED using Vuescan and the "long exposure pass". Ed
Hamrick said that the ccd was bleeding charge between sensors, causing
the problem. I have no reason to disbelieve him, but I found out that
if I manually expose at different exposure times and combine the scans
in Photoshop (which is what I think the long exposure pass does
automagically) I do not get these green spots. I don't understand it,
but I recommend doing it by hand.

A
 
Bart van der Wolf said:
The particular combination of Kodachrome dyes and LED spectral emission of
Don's Nikon scanner result in too low a signal for some channels. In that
case it could be a benefit to be able and adjust individual channel
exposure.
Click to expand...

That's his guess, but there are no numbers to back it up. I really
doubt that having the ability to separately control analog gain on
each channel will make the slightest difference in the resulting image.

It would be useful to see a raw scan file of an example of a
Kodachrome slide that needs separately controlled analog gain.

Regards,
Ed Hamrick
 
I never had these problems with the few Kodachromes I scanned on my
LS40.
Click to expand...

I believe LS40 has a Kodachrome mode, my LS30 does not.
But I would think that using advanced workflow together with long
exposure pass should solve the problem in vuescan. Did you ever try?
Click to expand...

Due to lack of individual Analog Gain control VueScan is incapable of
scanning dark Kodachromes on my LS30, but I don't like/use VueScan for
a variety of other reasons anyway.

I've been at this for almost a year now and - in my particular
situation - the solution seems to be to adjust individual Analog Gain
in NikonScan to get a reasonable dynamic range and then (if necessary)
contrast mask before doing the fine color balancing in Photoshop.

Don.
 
If this is the case for Kodachrome generally, I don't see why Ed does
not use differently balanced RGB exposure values as he does for color
negatives (in order to compensate orang mask)...
Click to expand...

I asked the very thing a while back and got an insolent response back
that dark Kodachromes with a heavy blue cast is "the default color
balance" and it's my fault for not liking it... :-/

Don.
 
I have had a problem with greeen spots showing older slides (of the
US-sponsored overthrow of Presideant Allende-ca. 1972?) that I scanned
with a Nikon 4000 ED using Vuescan and the "long exposure pass". Ed
Hamrick said that the ccd was bleeding charge between sensors, causing
the problem. I have no reason to disbelieve him, but I found out that
if I manually expose at different exposure times and combine the scans
in Photoshop (which is what I think the long exposure pass does
automagically) I do not get these green spots. I don't understand it,
but I recommend doing it by hand.
Click to expand...

Apparently, in order to get noise from the scanner you need to set
exposure time to several seconds which translates into several
thousand times the nominal exposure so I doubt that's the reason.

Reading about various other VueScan problems (e.g. the infamous
"pepper spots" with some scanners) I would not be surprised if it were
yet another bug, especially since you can remove the green spots by
doing it by hand. If relevant, maybe you can try a more recent version
of VueScan?

Don.
 
Hello, Alan
you wrote...
I have had a problem with greeen spots showing older slides (of the
US-sponsored overthrow of Presideant Allende-ca. 1972?) that I scanned
with a Nikon 4000 ED using Vuescan and the "long exposure pass".
Click to expand...

This was most likely the integer overflow problem in the blending
algorithm in vuescan that was corrected some versions ago...
 
Don said:
I believe LS40 has a Kodachrome mode, my LS30 does not.
Click to expand...

Neither scanner has anything in hardware that's used especially
for scanning Kodachrome. NikonScan for the LS40 has some improved
features, but this has nothing to do with the hardware.
Due to lack of individual Analog Gain control VueScan is incapable of
scanning dark Kodachromes on my LS30
Click to expand...

No, this is incorrect.

Regards,
Ed Hamrick
 
Don said:
I asked the very thing a while back and got an insolent response back
that dark Kodachromes with a heavy blue cast is "the default color
balance" and it's my fault for not liking it... :-/
Click to expand...

No, the response was that color balance and analog gain are
two different things. Analog gain is used to get most of the
pixel data stretched into the 10 bit samples, color balance
is done post-scanning.

You seem to believe that separately controlling the analog gain
of each channel will result in significantly better stretching
of the pixel data into 10 bit samples (on the LS-30), but seem
to confuse this with color balance.

I realize you're just being argumentative and have no real
interest in solving this with VueScan, but in the off chance
you're actually interested in investigating this, it would be
useful if you made available a raw scan file from a Kodakchrome
slide from your scanner that illustrates the problem.

Regards,
Ed Hamrick
 
I have had a problem with greeen spots showing older slides (of the
US-sponsored overthrow of Presideant Allende-ca. 1972?) ...
Click to expand...

The 11 of September of 1973.
Do you have photos of the military coup?

Geo
 
That's his guess, but there are no numbers to back it up. I really
doubt that having the ability to separately control analog gain on
each channel will make the slightest difference in the resulting image.
Click to expand...

Okey-dokey, here we go...

NOTE: I removed the watermark from VueScan images because it was
getting in the way. (I used unregistered version.)

For the record: Nikon LS-30, NikonScan 3.1, VueScan 7.6.84, 2700 dpi,
3600 x 2400 pixels
Photoshop preparation for upload: Reduced to 600 x 400, jpeg = 10.
Subject: Balcony, winter, around noon, snow, pigeon tracks (we all
know what color snow is...).


NikonScan - Baseline/Reference scan:
Auto Exposure = On
Nikon Color Management = Off
ICE = Off
AG = 0 (Reset)
As expected from an LS-30, the scan is dark and has a heavy blue cast.
===> http://members.aol.com/tempdon100164833/VS/NS-Base.jpg


VueScan mutilation #1:
Scan from: LS-30
Media type: Slide film
Bits per pixel: 48 bit RGB
Scan resolution: 2700 dpi
Exposure clipping: 0.1
Color balance: White balance
Slide vendor: Kodak
Slide brand: Kodachrome
I hope those are all the relevant settings. (It's hard to tell with
VueScan's hide-and-seek user interface.)
===> http://members.aol.com/tempdon100164833/VS/VS-1.jpg


VueScan mutilation #2:

These are trivial to scan with VueScan. Just set "Input|Media type"
to "Image" (not "Slide film"), preview the image, click with the right
mouse button (or holding down the control key on Mac OS) on a neutral
color, then press the Scan button.
Click to expand...

Settings same as above, except:
Media type: Image
After preview, right-click on the snow around the middle of the image.
(There's no feedback so I can't tell exactly where I clicked. I don't
know how to redraw the preview based on this right-click selection, so
I just right-clicked once and pressed the Scan button.)
===> http://members.aol.com/tempdon100164833/VS/VS-2.jpg


NikonScan using individual Analog Gain settings:
All settings same as baseline/reference scan, except Analog Gain:
Master = 2.0
Red = 2.0
Green = 0.8
Blue = -1.4 (note the minus sign)
This was very much quick-and-dirty. If I were to do this for real, I'd
fiddle around some more and then contrast mask to recover burnt out
highlights. However, it's quite clear that - even with this cursory
adjustment - the dynamic range has been boosted considerably to enable
meaningful post processing.
===> http://members.aol.com/tempdon100164833/VS/NS-AG.jpg


Now, I have always tried to be fair so to show (once again) that I'm
trying to be objective, I'll play my own devil's advocate. Here's an
example of a VS scan that does work just fine (using the same settings
as in the first VS scan above):
===> http://members.aol.com/tempdon100164833/VS/VS-OK.jpg

Of course, NikonScan also works without problems with such a slide.
There's enough dynamic range to color balance later without having to
use individual Analog Gain, although using it doesn't hurt either.

But to dogmatically state that individual Analog Gain is not needed
is, I'm sorry, just patent nonsense - as just demonstrated above - and
only damages credibility of anyone making such blanket statements.

Don.
 
No, the response was that color balance and analog gain are
two different things. Analog gain is used to get most of the
pixel data stretched into the 10 bit samples, color balance
is done post-scanning.
Click to expand...

I'll let you argue with yourself:

--- cut ---
LS-30 works fine with Kodachrome.
You just don't like the default color balance.
Click to expand...
--- cut ---
You seem to believe that separately controlling the analog gain
of each channel will result in significantly better stretching
of the pixel data into 10 bit samples (on the LS-30), but seem
to confuse this with color balance.
Click to expand...

No, I do not believe either of those statements and have said so
repeatedly and unambiguously:

--- cut ---
Forget color balance, how about using Analog Gain to extend dynamic
range?

Given an image with the following histogram highlights (after
adjusting Master AG):

Red - around 120
Green - around 125
Blue - around 250

Setting the neutral point post-scan will *not* recover the missing R &
G range (it will just cause banding). Using individual Analog Gain
will.
Click to expand...
--- cut ---

In other words and taking the above example, once Master Analog Gain
is boosted so that the blue channel starts clipping i.e. bumps up
against 255, while red is still loitering around 120, the dynamic
range of the red is stuck at 120 or less if it doesn't start at 0.
That's just not enough for any meaningful editing without introducing
artifacts, yet the Master AG can't be boosted anymore because that
will cause blue to clip significantly.

By selectively boosting red (and maybe cutting blue) the red's dynamic
range will be extended significantly without clipping the blue. At the
very least, it will be boosted sufficiently to perform editing without
resulting in artifacts.

If this individual Analog Gain adjustment results in better color
balance, so much the better. It's the cherry on top, but not the
immediate goal.
I realize you're just being argumentative and have no real
interest in solving this with VueScan, but in the off chance
you're actually interested in investigating this, it would be
useful if you made available a raw scan file from a Kodakchrome
slide from your scanner that illustrates the problem.
Click to expand...

Let's see first what you think of the images I just posted...

If I were argumentative I wouldn't go out of my way every time to
indicate that others may differ, I wouldn't acknowledge there are many
happy VueScan users, nor would I take the trouble to upload an image
to prove that VueScan can work as I just did (!), etc, etc...

However, that doesn't mean I will take any old statement at face value
if it's illogical, changes the subject, it's evasive, doesn't make
sense or is plain wrong.

So, I think you may need to re-calibrate your objectivity. ;-) It
seems to have acquired a dark, blue cast - not unlike Kodachromes -
which is not that surprising since you consider that the "default
color balance"... ;o)

Don.
 
Neither scanner has anything in hardware that's used especially
for scanning Kodachrome. NikonScan for the LS40 has some improved
features, but this has nothing to do with the hardware.
Click to expand...

The subject was not hardware but software. Therefore, the key question
is does NikonScan on LS40 have a Kodachrome option turned on or not?

If it does (which is what I believe, but don't know for sure) then
that explains why Erik had no problems with Kodachromes.

If it doesn't, then Erik knows what he's doing and managed to wrestle
the LS40 to the ground on his own. ;o)
No, this is incorrect.
Click to expand...

As can be read here repeatedly, others who do not have a vested
interest (and sporting other Nikon scanners as well) seem to think it
is correct.

Don.
 
(e-mail address removed) (Don) wrote in @news.individual.net:
Subject: Balcony, winter, around noon, snow, pigeon tracks (we all
know what color snow is...).
Click to expand...

Don't eat the yellow snow!

Sorry, couldn't resist...
 
Back
Top