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

Discussion in 'Nikon' started by Gary Whitehead, Aug 16, 2004.

  1. 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!
     
    Gary Whitehead, Aug 16, 2004
    #1
    1. Advertisements

  2. Gary Whitehead

    RSD99 Guest

    Sounds good ... but jus to be sure include a raw scan of a well-known target ... such as
    an IT-8 target for which you have the data, or an image of an Macbeth color checker ...
    with your archives.
     
    RSD99, Aug 16, 2004
    #2
    1. Advertisements

  3. Gary Whitehead

    Greg Guest

    Go for it.

    The scanner hardware, I believe, *always* scans with a gamma of 1, with the
    gamma adjustment
    being performed by software.

    The *only* reason I don't use a gamma of 1 is that the profiler I use (the
    Little CMS scanner profiler)
    will only use 8-bit scans. If I feed the profiler higher bit depth target
    scans, the profiler definitely
    does not make use of the extra resolution. So, I use a gamma of 2.2 to get
    around this problem.

    I think your workflow makes complete sense, and aside from the difference in
    gamma, it's
    the same as my workflow for all intents & purposes.

    Greg.
     
    Greg, Aug 16, 2004
    #3
  4. Gary Whitehead

    Greg Guest

    Good point - I forgot to mention that I use JPEG 2000 to archive my scans.

    Gary - I suggest you look into JPEG 2000 as a possibility for storing your
    achives. JPEG 2000 supports greater than 8-bit per channel encoding, whereas
    standard JPEG doesn't.

    Yes, I use JPEG 2000 in lossy mode, but it does have a lossless mode as
    well.

    Greg.
     
    Greg, Aug 17, 2004
    #4
  5. DAT tapes!

    Having the disc space for this is not a problem nowadays, but I certainly
    would not be doing it without backup. The entire collection should fit on
    around 30 tapes (12GB), at a cost of about 150 euros.

    I'm also reckoning on us being at a cusp, i.e. in a few years the amount of
    data that this will produce will fit easily into normal spec machines.

    Cheers,

    Gary.
     
    Gary Whitehead, Aug 17, 2004
    #5
  6. And here I'm up to something on the order of 2 sets of 60 DVDs plus a
    complete backup on a second computer. I have about 3,000 to 4,000
    negatives left to scan and about a 100# worth of *old* prints all the
    way back to tintypes and the "petrified cardboard" prints.
    The unedited TIFFs run about 60 megs each.

    All slides and negatives are indexed in notebooks.

    Roger Halstead (K8RI & ARRL life member)
    (N833R, S# CD-2 Worlds oldest Debonair)
    www.rogerhalstead.com
     
    Roger Halstead, Aug 17, 2004
    #6
  7. Gary Whitehead

    Al Guest

    You have an excellent film scanner there. Though I may not know much about
    that type of scanning, at 4000dpi x 3-4000 scans, I'm assuming you have a
    terrabyte server handy :)

    I can only assume that if you scan at a default 1.0 gamma, you still have
    more than enough information to change it to a better gamma/icc profile
    through photoshop, possibly even through using a repetitive action. But I
    also think that not all pictures will be the same, therefore a pic that
    looks decent with a gamma 1 may not be applicable to another pic. But
    that's just my newbie thinking ;)

    Good luck anyway in whatever you choose to do.

    Al
     
    Al, Aug 18, 2004
    #7
  8. On Mon, 16 Aug 2004 22:52:30 +0200, Gary Whitehead

    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.
    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 been using the same since some where around Feb., or March.
    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.
    My experience, using the SF210 automated slide feeder using digital
    ice only will be roughly 30 to 40 seconds per image.
    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
     
    Roger Halstead, Aug 18, 2004
    #8
  9. Long term, I do not see too much of a problem in that relatively cheap
    devices that can hold the entire collection without raising a sweat are
    only around the corner - 300GB consumer drives are now available. Then I
    can easily manage redundant online storage.

    Short term I will have the set online on my server (for myself and my
    girlfriend I run a house (Linux) server, files, printing email etc), and
    rely on DAT tape for the offline backup. Basically, I can manage it now
    (with some hassle) and have redundancy, and wait in hope for the whatever
    cheap terabyte devices that are available in a couple of years. DAT tapes
    are advertised to have an archival lifetime in the range of at least a
    decade (and tape is a mature technolgy) which is much longer than I intend
    to rely on them for. They are also relatively cheap in cost/GB.
     
    Gary Whitehead, Aug 18, 2004
    #9
  10. Aye, but I plan to have them online as well (a couple of discs nowadays),
    the tape is for redundancy. However, I must admit that restoring the
    collection in the case of a disc failure would not be fun (c3hrs per tape).
     
    Gary Whitehead, Aug 18, 2004
    #10
  11. I have been thinking about this and looking at my scans of the IT8 targets.
    I don't think that it actually matters much that we profile the scanners
    using 8 bit scans.

    Reasoning:

    1. The scanned targets are actually quite noisy (film grain/target surface),
    giving in the midtones (using Photoshop's histogram tool) a standard
    deviation ~4-5bit (out of 256) on each channel, and maybe 1.5bits in the
    highlights, and 0.5bits in the shadows (for a single target square).
    Before anyone shouts at Wolf Faust, as I will explain below this is "Good
    Thing".

    2. At 4000dpi we are averaging around 10000 samples for a colour square and
    maybe 40000 for a greyscale square. The resolution of the average can be
    approximated to the standard error which will be

    SD/SquareRoot(NoOfSamples).

    This gives me in the case of the midtones a standard error of around 1/25th
    of a bit for a colour square, which is almost an extra 5 bits of precision,
    i.e. around 13bits. No useful improvement would be seen by using a 16 bit
    scan. The other way of looking at it is that the quantisation noise of
    8bit sampling (0.5bit) is insignificant compared to the target noise.
    (Errors should be added as a sum of squares).

    This is actually a standard technique in digital measurement, where it is
    recognised that the mixture of some noise (greater than the bit resolution)
    and averaging multiple samples allows sub bit resolution.

    The only area that I have some doubt on this argument is in the deep
    highlights (1-3 bits) and shadows. It is possible that there may be some
    clipping of the noise component which would tend to shift the average
    towards the midtones. I will take a look at a 16bit image later which I
    will range expand (i.e. expand levels 0-2 -> 0-256). The test here is
    whether I see a normal distribution of points. If I do, then this should
    also be safe at the extremes.

    Of course this does all depend on the profiler perfoming its calculation in
    a sufficiently accurate data type and exporting the profiles in 16bits.
    Little CMS does appear to use the LUT16Type in its output, but I have not
    checked the code to see how it is calculated.
     
    Gary Whitehead, Aug 18, 2004
    #11
  12. Gary Whitehead

    Greg Guest

    Gary,
    I have not digested your notes in detail yet, but, I do know that the
    version of the Little
    CMS profiler I am using definitely will *not* use anything greater than
    8-bits per channel
    in the IT8 scans - I have even had this confirmed by the author himself. It
    will load
    the scan and process it, but it will not use the extra precision - it will
    discard it.
    Because of this, the author himself has said that it is very important *not*
    to use a gamma
    1 scan - it is important to use a perceptually uniform gamma, such as 2.2.
    As you say, this issue is specific to the profiling software - other
    profilers which really
    can use the full precision would be entirelly suitable for use with gamma 1
    IT8 target
    scans.

    Now, after saying all this, I am not sure whether there is a more recent
    version of the
    profiler available now - it's possible that this limitation has been
    removed.

    Greg.
     
    Greg, Aug 19, 2004
    #12
  13. I hope to end up with a pair of 320s on each of three machines with a
    serial RAID on the 4th. That 4th machine is remote in another
    building.
    Currently I run redundant on line (mine) storage as do you.
    I have the work machine, one for backup and archive on DVD.

    I figure Hard drive data should be refreshed at least once a year if
    not more often. So far I've had good luck and it's quite fast across
    the 100 Mbps network.
    I have close to that now across my network at a relatively reasonable
    cost. Going to the 6 300 Gig plus drives and the serial RAID will not
    be trivial. They will make the 3 to 4 gig dual processor machine
    coming up look pretty reasonable.

    I run too much *stuff* and can bog down a single 2.8 gig processor.
    True, but with he advertised life of a decade I'd want to refresh at 5
    years, which is only three refreshes over 20 years.
    Good luck, It sounds like you have thought out your system well.

    Roger Halstead (K8RI & ARRL life member)
    (N833R, S# CD-2 Worlds oldest Debonair)
    www.rogerhalstead.com
     
    Roger Halstead, Aug 19, 2004
    #13
  14. Gary Whitehead

    Greg Guest

    Gary,
    I have checked with the author (Marti Maria), and there is in fact a new
    version of the scanner
    program, available here: http://www.littlecms.com/profiler_qs.htm and this
    really
    does work with high resolution scans, and so in theory, gamma 1 should be
    safe.
    Marti cautions us that a) there is no support, and b) we should test it
    thoroughly
    with gamma 1 before relying on it too much, as gamma 1 still needs great
    care.

    If this is the version you're already using, then ignore my earlier warning.

    Greg.
    p.s I post this information with permission from Marti.
     
    Greg, Aug 19, 2004
    #14
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.