Archiving: TIFF or PSP, 16 bit or 8 bit?

Discussion in 'Photoshop' started by Robert A, Apr 4, 2004.

  1. Robert A

    Robert A Guest

    Two questions, same subject:

    How do you permanently archive your Vuescan files? Do you leave them in the
    native TIFF format, or convert them to PSP? Moreover, do you leave them in
    the original 16-bit, or convert them to 8-bit to save space?

    -Robert Ades
    Robert A, Apr 4, 2004
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  2. Robert A

    Mike Russell Guest


    CD's and hard drive space are cheap. Archive your original raw scans, and
    save your corrected images as well on the same disk. The amount of work
    required to do each scan is much more important than the amount of storage

    If you have so many scanned images that the number of CD's is oppressive,
    either switch to DvD, or consider saving as 8 bit tiff.
    Mike Russell, Apr 4, 2004
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  3. Robert A

    Robert A Guest

    Mike, my 4000-dpi 16-bit scans take up more than 100Mb each. Normally when
    working in Photoshop, I convert to 8-bit right away. The reason I scan in
    16-bit is for greater dynamic range and shadow detail. Once the scan is
    done, is there any useful reason to keep that 16-bit data?

    Robert A, Apr 4, 2004
  4. Robert A

    Mike Russell Guest

    Are you scanning medium format? I wonder if you are getting any additional
    resolution over, say, a 25 or 50 meg scan. Have you experimented and can
    you see the difference on your prints? You may even be losing sharpness by
    scanning at too high a resolution. Scanning at a high resolution introduces
    softness, which you must then compensate for by sharpening.

    But back to your question. Volumes have been written on the topic of 8 bits
    versus 16, and I have contributed some bulk to that discussion.

    My personal conclusion is that 8 bits per channel is plenty for today's
    technology, and the evidence I offer is that (for a gamma 1.8 or greater
    image) it is impossible to tell by looking, and looking, after all, is what
    we do with photographs.

    But there are those for whom that argument is not convincing, and the act of
    throwing away any image data is not something they can justify. Whether I
    agree with the technical reasons for this extra data, I have to say many of
    these people do create better photographs and prints than I do.

    So, pick which side of the fence you want to be on. Above all keep your
    originals in a safe place - scanners can only continue to get better and
    Mike Russell, Apr 4, 2004
  5. Robert A

    Uni Guest

    If you prefer discard critical color information, reduce them to 8 bit.

    Uni, Apr 5, 2004
  6. Robert A

    Robert A Guest

    I'm scanning 35mm. I scan based on the intended print size, so for 13x19, I
    use 4000 dpi, for smaller prints, I adjust accordingly. I always scan at
    16-bit (actually 14-bit with my Canon FS4000US) to a TIFF file.

    Once in Photoshop, I adjust levels in 16-bit if necessary, then convert to
    8-bit and make all the remaining adjustments for final output in a PSP file.
    I know that my Epson 2200 printer only utilitizes 8-bits/channel, so I see
    no point in preserving 16-bit data for current prints. But I still retain
    the original TIFF file in 16-bit, unretouched or modified in Photoshop for
    later archive.

    My understanding is that it's important to SCAN in the highest bit depth as
    possible, but once you have the file in your computer, there's little if any
    use for the extra bits in terms of archiving. Is there any general
    agreement on this?

    Robert Ades
    Robert A, Apr 5, 2004
  7. Certainly don't even consider PSP as an archive format, it is a
    proprietary coding scheme which may not be supported in the future. TIFF
    is an open coding scheme which is supported by virtually all image
    processing applications and will not only continue to be supported but
    continue to develop.

    The 16/8-bpc argument continues, but I have yet to see any evidence in
    favour of 16bpc archiving, despite Dan Margulis issuing and open
    challenge for anyone to demonstrate an image which could be achieved in
    16bpc processing which could not also be achieved in 8bpc processing
    over three years ago. Given that failure, the generally accepted
    principle is to scan in 16bpc, or the greatest available bit depth of
    the scanner, optimise the image in terms of gamma and levels before
    archiving in 8bpc format.

    No doubt such sacrilegious advice will solicit much consternation and
    opposing views amongst the collective. ;-)
    Kennedy McEwen, Apr 5, 2004
  8. On what equipment are you experiencing this particular kind of madness.
    Scanning at an increased sampling density may not offer any more
    resolution in the image, but it certainly cannot make it any less sharp
    or softer!
    Kennedy McEwen, Apr 5, 2004
  9. Robert A

    Hecate Guest

    ;-) Only slightly..

    I prefer to scan at the highest bit depth possible, do nothing to the
    file, and then archive it to either/both DVD and a firewire hard disk.

    Then, I work on a copy of that file. It means I always have the 16 bit
    file to fall back on should something disastrous happen. I used to
    work in computer support and I've seen too many screw-ups which
    resulted in original files being trashed with nothing to fall back on.

    Anyway, that's my excuse - maybe I'm just paranoid ;-0
    Hecate, Apr 5, 2004
  10. Robert A

    Mike Russell Guest

    As you approach the Nyquist frequency, certain frequencies are reduced in a
    very predictable way. This is softness.

    Artificially boosting those frequencies yields a better approximation to the
    original image's frequency distribution, and a more natural appearance.
    This is sharpening.
    Mike Russell, Apr 5, 2004
  11. Robert A

    Robert A Guest

    But is there any benefit to having a 16-bit backup?
    Robert A, Apr 5, 2004
  12. Robert A

    Wayne Fulton Guest

    Not likely, if it already appears as a halfway decent image.

    16 bits may be useful for the extreme tone-shifting adjustments,
    like gamma specifically, but histogram B&W Points or Curve too
    (the latter is of debatable benefit, but it is popularly done as 16b).

    If we are scanning and saving RAW data (no adjustments done), then 16
    bits is good, since all of these operations are still to come. This
    would be the purpose of 16 bit data.

    But if these operations are already generally done (and archive seems to
    imply that), then there would be no point of saving 16 bits.
    Additional fine adjustments dont need 16 bits at all.

    Printers and video are 8 bit devices.
    Wayne Fulton, Apr 5, 2004
  13. Robert A

    Uni Guest

    Uni, Apr 5, 2004
  14. This is a contradiction of your earlier statement, since scanning at a
    higher resolution (ie. increased sampling density) results in a higher
    Nyquist limit and thus, by your latter argument, shifts the onset of
    this "softness" to higher spatial frequencies in the image. In short,
    your latter argument indicates that scanning at a higher resolution
    results in *less* softness, not more, in an image scaled at the same
    size! Which argument are you making?

    The reproduction of spatial frequencies are reduced by the MTF of the
    scanner, which decreases not only as you approach Nyquist, but
    throughout the spatial frequency range, usually monotonically from a
    maximum at zero cy/mm. Sampling density merely determines where on
    that MTF curve the Nyquist limit sits. As sampling density increases,
    more of the total MTF range is included in the spatial frequency range
    that can be unambiguously reproduced - so more information is resolved,
    not less. Clearly this is an issue of diminishing returns, but the
    result is always positive - more total detail resolved, not less and
    certainly not more "softness". In some systems it is possible to sample
    such that the Nyquist limit lies beyond the limiting MTF of the scanner
    (eg. most flatbed scanners) thus meeting the criteria for total
    elimination of aliasing. In such cases, increasing the sampling density
    will not gain resolution, but neither will it increase image softness -
    the end result is just more data representing the same image information
    Kennedy McEwen, Apr 5, 2004
  15. That is the $64k question. As mentioned, the general consensus is that
    after level adjustments are made there is little point in retaining the
    additional bits. As mentioned, the challenge is still out there to
    provide examples where this is not the case, but I am not aware of
    anyone having successfully done that (though quite a few have tried).
    Kennedy McEwen, Apr 5, 2004
  16. I have built systems (monochrome as it happens, but that shouldn't
    influence the result) with 12-bit ADCs on the video channel output. The
    difference cannot be perceived, but it is something the marketing folks
    like to exploit. ;-)
    Kennedy McEwen, Apr 5, 2004
  17. Robert A

    Mike Russell Guest

    Certainly I agree that a higher scan rez extracts more information.

    My point is that sharpening is an indispensable step after resampling. That
    resampling may be explicit, as when you resize an image in Photoshop, or it
    could be implicit, as when a large image is printed at a small size.

    For example, the original poster scans to 150 meg - if that is printed at
    8x10 without sharpening, it will be softer than an image scanned at a lower

    I believe this is supported by theory, as I described, and by common
    practice in the industry. If you disagree, or if you believe that
    sharpening is otherwise not needed, I'm interested in your explanation.
    Mike Russell, Apr 5, 2004
  18. Robert A

    Toby Thain Guest

    Not true; the Paint Shop Pro file format (at least through v8) is
    documented[1], as are its compression schemes (RLE and LZ77[3]). As
    proof of this, I have written a PSP format plugin for Photoshop[2]
    which is interoperable with PSP 5-8 *and released as open source under
    the GPL*. It is a more open format, for example, than Photoshop PSD or
    PSB; documentation for those is not freely available.

    Arguments for or against archiving in PSP format might perhaps take
    into account issues such as metadata and colour profiling. For
    interoperability with non-proprietary tools, standardisation and
    "future-proofing", TIFF or JPEG seem very good choices.


    [3] A PSP-compatible FREE implementation of LZ77 exists:
    Toby Thain, Apr 5, 2004
  19. But as you can see, from your first quoted line above which you have
    conveniently retained throughout this thread, your statement concerned
    high resolution scanning, not resampling.
    Kennedy McEwen, Apr 5, 2004
  20. As were the technical details of Betamax!

    It's specification may be available but it is still a proprietary format
    that is, in the main, only supported by JASC software and owned by them.
    Remember the GIF format and the Unisys debacle?

    Nobody else really bothers with PSP simply because it offers little that
    is not already available or bettered in industry standard formats. TIFF,
    in particular, supports a wide variety of compression techniques or,
    indeed, no compression at all, making it completely immune from Unisys
    type action.

    Folks will be using TIF and JPG formats long after JASC have gone bust
    or attempted to revoke the licences for PSP.
    Kennedy McEwen, Apr 5, 2004
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