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

On Mon, 16 Aug 2004 22:52:30 +0200, Gary Whitehead
wrote:

Hi Gary,

As I mentioned in a previous post I've gone through many a thousand
images so far. They ranged from Kodachrome (many versions with some
as old as 50 years) Ektachrome, and a wide variety of 35mm negatives.

It might help if you sort your slides by age, but you will find some
pretty wide variations.

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 think the backup is a good idea, but if the slides were properly
processed they will probably be around in good shape longer than the
original digital media to which you save 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

I've been using the same since some where around Feb., or March.

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).

At that resolution and depth the basic slide with no cropping will run
about 126 to 130 megs. That comes out to about 520 Gigs of storage.
or about 113 DVDs.

I scan at 8 bits and haven't found any reason to go beyond that. The
files are still roughly 60 megs as TIFFs.


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

My experience, using the SF210 automated slide feeder using digital
ice only will be roughly 30 to 40 seconds per image.

* 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

Here lies a problem. To maintain data integrity you are going to have
to refresh it at least once every ten years, or more frequently, as
there is no real data to support storage life beyond that. Beyond a
few years data lifetime is based on accelerated lifetime testing and
projections.

When archiving, the general approach is to make two copies and store
them in separate locations that are friendly to the medium. (Dark,
with temperature and humidity control)

As you are not going to be using a rolling backup that rules out
magnetic storage. Tapes and hard drives may have lifetimes of many
years, but the lifetime to maintain data integrity is very short.

Even with today's advances in hard drives which last 100s of thousands
of hours you can not depend on that kind of life for the data.
Typically HDs are refreshed on a monthly basis. I'd not want to trust
one even in storage beyond a year.

Optical on the other hand is potentially very long lived, but not
proven. How long a particular medium remains viable (will the hard
ware remain available to read and write said medium) and what media is
practical for the amount of storage you need? Beyond 10 years there
is the very real possibility of the need to change to a different
media.

Currently about the only thing I see that would meet the goal are DVDs
and they come with no guarantee, only a projected lifetime.
Unfortunately DVDs tend to vary in quality and can be susceptible to
damage from handeling, which pretty much describes most optical disks.

Store them on edge in Jewel cases and keep away from sun light. They
should also be kept in a relatively low humidity and cool, but not
cold temperatures. Check the manufacturers specs on storage. Above
all, do not flex DVDs as most do when taking them out of the case.
Press down in the center of the case and the DVD will pop out. Do not
pull up on the edges. That will cause flexing and the DVD is a two
layer device which can separate, or fracture.

You are really on your own as far as quality control and how often you
check them for data integrity. If you ever find a corrupt file you
know you have waited too long. Hopefully the ones on the second backup
will still be good, or at least the same files will not have failed.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
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!