Archival scans, 48bit, Nikon Coolscan 5000 ED, ? Gamma 1.0 ?

  • Thread starter Thread starter Gary Whitehead
  • Start date Start date
G

Gary Whitehead

Hi All,

I wish to scan ~3-4000 slides, for two reasons, one to have the images
available electronically but mainly to have a safe archive/backup of the
images (most of these slides cover the period when I used to work for
the British Antarctic Survey, are c20 years old and I would be gutted if
I lost them...).

I've had a Nikon Coolscan 5000 ED for a couple of months, and have spent
the time becoming familiar with it.... and colour management. On the
colour management issues I am now just starting to get a good overall
idea of how things work (and I must admit it was not simple, and I am
speaking as a lapsed physicist!).

I would like to scan these slides ONCE - i.e. I would like to get it
right the first time. I intend to scan at 48bits and 4000dpi (i.e. the
max resolution of the scanner).

Can anyone comment on the scenario below:

---------------------

* 16bits/channel / 4000dpi
* Raw scanner RGB at - gamma 1.0 - (Nikon colour management turned off).
* Only processing performed by the scanner being digital ICE
* Scanner calibrated using it8 targets and resultant icc profiles used
to perform conversion to the working colour space (presently Wide Gamut
RGB) on import of the raw gamma 1.0 files to Photoshop

----------------------

I am aware that there is a somewhat heated discussion on the subject of
gamma 1.0 editing, which is not what I am proposing here. My concern is
complete retention of the data delivered by the scanner. My reasoning is:

* The scanner sensor has a 16bit resolution.
* I acknowledge the sense in outputing a higher gamma file when using 8
bits/channel in order to space the resultant resolution perceptually.
However when performing such a transform on the full bit data all I see
is an increase in spacing of the scanner resolution at the shadow end at
the cost of lost information in the highlights. I.e. I see no gain.
* The scans are archival - I might wish to use the data in a couple of
decades, with display technologies that may be completely different from
today (i.e. why gamma encode the data with a value that derives from
today's display technology).

I would be particularly interested to hear from people in the high gamma
camp(!), since I would guess from the gamma 1.0 camp I am going to hear
"Go for it". The only potential problem that I can see here is whether
the application of a gamma 2.2 curve through Photoshop/icc profile is
any less accurate than in the scanner itself. I acknowledge that there
may be others I have missed....

Cheers,

Gary Whitehead.



N.B. I too fought with the colour management on the scanner, and gave up
in near disgust. Wolf Faust's targets, and resultant ICC profiles gave
the best results I had seen within minutes of generating them!

Apologies for cross posting - I missed this high volume group in the
first trawl.
 
i assume you want to set the black point and white point on each image
to use the full capability of the scanner's dynamic range ?


Have you considered Silverfast Ai with HDR ?

Frank
 
Gary Whitehead said:
Hi All,

I wish to scan ~3-4000 slides, for two reasons, one to have the images
available electronically but mainly to have a safe archive/backup of the
images (most of these slides cover the period when I used to work for
the British Antarctic Survey, are c20 years old and I would be gutted if
I lost them...).

I've had a Nikon Coolscan 5000 ED for a couple of months, and have spent
the time becoming familiar with it.... and colour management. On the
colour management issues I am now just starting to get a good overall
idea of how things work (and I must admit it was not simple, and I am
speaking as a lapsed physicist!).

I would like to scan these slides ONCE - i.e. I would like to get it
right the first time. I intend to scan at 48bits and 4000dpi (i.e. the
max resolution of the scanner).

Can anyone comment on the scenario below:

---------------------

* 16bits/channel / 4000dpi
* Raw scanner RGB at - gamma 1.0 - (Nikon colour management turned off).
* Only processing performed by the scanner being digital ICE
* Scanner calibrated using it8 targets and resultant icc profiles used
to perform conversion to the working colour space (presently Wide Gamut
RGB) on import of the raw gamma 1.0 files to Photoshop

----------------------

I am aware that there is a somewhat heated discussion on the subject of
gamma 1.0 editing, which is not what I am proposing here. My concern is
complete retention of the data delivered by the scanner. My reasoning is:

* The scanner sensor has a 16bit resolution.
* I acknowledge the sense in outputing a higher gamma file when using 8
bits/channel in order to space the resultant resolution perceptually.
However when performing such a transform on the full bit data all I see
is an increase in spacing of the scanner resolution at the shadow end at
the cost of lost information in the highlights. I.e. I see no gain.
* The scans are archival - I might wish to use the data in a couple of
decades, with display technologies that may be completely different from
today (i.e. why gamma encode the data with a value that derives from
today's display technology).

I would be particularly interested to hear from people in the high gamma
camp(!), since I would guess from the gamma 1.0 camp I am going to hear
"Go for it". The only potential problem that I can see here is whether
the application of a gamma 2.2 curve through Photoshop/icc profile is
any less accurate than in the scanner itself. I acknowledge that there
may be others I have missed....

Cheers,

Gary Whitehead.



N.B. I too fought with the colour management on the scanner, and gave up
in near disgust. Wolf Faust's targets, and resultant ICC profiles gave
the best results I had seen within minutes of generating them!

Apologies for cross posting - I missed this high volume group in the
first trawl.
Click to expand...

Would 48bit rgb (or 64 bit, including infrared channel) gamma 1
Vuescan raw files do? And bring up the gamma through Vuescan
scan-from-disk?
 
degrub said:
i assume you want to set the black point and white point on each image
to use the full capability of the scanner's dynamic range ?


Have you considered Silverfast Ai with HDR ?

Frank
Click to expand...


Silverfast, I did, but just too expensive - I have to stop spending at some
point. My main interest was in the icc profiling, and I have now
determined that I can do it with freely available tools, and secondly, so
long as I keep the orginal it8 target scans I can always reprofile if
better tools become available.

One point that I have been wondering (linked to your black and white point)
is the issue of autoexposure in the scanner. With NikonScan I cannot find
any method of setting a manual exposure (exposure compensation, Yes, but to
be sure that I am getting the same exposure each time, No) - unless anyone
can point out that I have missed anything. Does this affect the validity
of a profile (my thinking is it must somewhat, especially if any of the
transformations are non linear).

Cheers,

Gary.
 
Mendel said:
Would 48bit rgb (or 64 bit, including infrared channel) gamma 1
Vuescan raw files do? And bring up the gamma through Vuescan
scan-from-disk?
Click to expand...

Vuescan seem a rather good tool for its price, and I have purchased a copy
(if nothing else allows me to use my scanners when in Linux).  The only fly
in the ointment for me is that its handling of defect removal is poorer
than ICE, especially for "pepper grain".

I have tried it as a profiling tool, and it does seem to work quite well,
and of course as you say it can be used to convert to a working colour
space.
 
Gary Whitehead said:
* The scanner sensor has a 16bit resolution.
* I acknowledge the sense in outputing a higher gamma file when using 8
bits/channel in order to space the resultant resolution perceptually.
However when performing such a transform on the full bit data all I see
is an increase in spacing of the scanner resolution at the shadow end at
the cost of lost information in the highlights. I.e. I see no gain.
Click to expand...

On the other hand, you don't see any real loss, because your scans have
been transformed into "perceptual space". In short, the information
discarded in the highlights was imperceptible to begin with, whilst the
increased histogram spacing in the shadows merely indicates the limited
bit depth of the scanner in that "perceptual space". In short, your
scanner sees linearly but you see logarithmically.

It is just a coincidence of nature that the gamma law of the CRT is
approximately the opposite function of the perceptual response of the
eye over the levels of illumination that are relevant here. So, unless
you are expecting some future technological developments to change the
operating principles of your eyes, it does not make one iota of
difference whether you archive in gamma 1.0 or gamma 2.2. Ultimately
you will need to convert it to gamma 2.2 for use, and you will lose just
as much data then (perhaps more - see the discussions on PS limitations)
as you think you are losing now.
 
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