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Thread: "small" .tif or large jpeg

  1. #1

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    "small" .tif or large jpeg

    Following on a recent thread pointing to the "scan once, readjust master from there" I have a high end problem. I'm the imaging guy (among various hats, shoot AS 4x5 for fun) at a midsized museum and have been charged with scanning some plates from an old (1828) and even rarer book (book is not bound, so no issues there). I have an Epson 4990. Scan options are:

    - scan at 2400 dpi to get 2.26 GB 48 bit RGB .tif file. Then resize image to fit on CD-ROM for archiving (700 MB 48 bit RGB .tif). DVDs still have too many cross-platform issues, so is not an option.
    [LZW compression *increased* file size to 2.83 GB].
    - Take 2400 dpi 48 bit scan and jpeg it at highest quality with associated 24 bit conversion, producing files of around 250-320 MB. Neither the Epson scan nor Silverfast will allow me to scan at higher resolution than 2400 dpi because of some file size limitation.

    So the options for archiving on CDs are "small" 48 bit RGB .tif, or pixel-wise larger highest quality jpeg in 24 bit RGB. Needless to say, that the jpeg master would be converted to .tif before any work is done on it. The question is, what produces overall the better master file?

    I think intuitively that the jpeg route is better as there is so much more pixel information available, which will outweigh the loss of tonality due to the 48 to 24 bit conversion; tonality is not that much of an issue as the images are some sort of lithography (I think), so more colorized line-art than continuous tone photographs. The tif would be area-wise over three times smaller, or in linear dimension around 1.7-1.8 times smaller. Am I overlooking something?
    Daniel Geiger
    geiger at vetigastropoda dot com

  2. #2

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    Re: "small" .tif or large jpeg

    You might consider saving at the larger size in 16 bit JPEG-2000 format.

  3. #3

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    Re: "small" .tif or large jpeg

    How about a 24 bit TIFF?

  4. #4

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    Re: "small" .tif or large jpeg

    Unless you plan on studying the individual fibers in the paper, 2400 is overkill for scanning paper, esp. as the real resolution of the 4990 is significantly less than that. 1200 would be more than enough, and you could probably downsize to 600 with no loss in info. That would save a huge amount of space.

  5. #5

    Re: "small" .tif or large jpeg

    "The question is, what produces overall the better master file? "

    I agree completely with Ed, and further, I suggest saving as TIFF rather than JPEG. JPEG is going to lose something. But then maybe for this project that's not important?

    I'd only go for the huge files if your display department wanted to make giant reproductions and needed the resolution. (Which might happen later even if they think otherwise now.)

    Doesn't your organization have a standard practice for digital image archiving? CDs aren't very permanent. But you didn't ask about that.

  6. #6

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    Re: "small" .tif or large jpeg

    True optical resolution is certainly a good point. Then an adjusted 24 bit TIFF is perfectly fine and fits on the inferior CDs. Re study of paper fibers, the biggest problem I have is that the final purpose is not defined (despite requests for clarification on that key point). So, when in doubt, scan at higher resolution, to be on the safe side. Also consider cropping, and what ever else Exhibits/Marketing will come up with.

    Re institutional standards, we are a small place, with relatively few digital assets. While I store my personal stuff on RAID5 arrays, at work that's a dream still a long time away. We do have GB intranet with some servers, but based on some past hick-ups, I am pretty sure it's not RAID of any sort. I am the guy who is most versed in the digital imaging area (isn't that scary), and use my personal scanner as it is the best on around. Disregarding these minor issues, greatest workplace ever. Seriously.

    Thanks to everybody.
    Daniel Geiger
    geiger at vetigastropoda dot com

  7. #7

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    Re: "small" .tif or large jpeg

    If fitting it on a CD is the main problem, you can always use a compression/archiving utility such as zip and then span it over several CDs. What I would do if I were you is this:

    1. Create the highest resolution and quality scan possible and save it as TIFF. While neither you nor museum need this kind of quality now, why limit future options by today's needs?

    2. Use one of the widely available archiving/compression utilities such as zip (not too expensive and pretty capable) to create compressed archive spanned over several CDs.

    3. Create at least one extra copy of this set for redundancy, two would be better - CDs are cheap.

    4. Downsize the original to fit one CD and use it as a working copy.

    5. As above, create another copy of this CD, two would be better.

    This way, you will have the best of both worlds with relatively reasonable safety, insofar as CDs can be considered safe long-term storage, but that choice has already been made for you and you're trying to deal with it through redundancy.

    If you really wanted to be secure, copy each set of archived (high resolution) CDs to a fresh set every few years. For really critical work, uncompress, test and then re-compress fresh using the newest version of the utility.

    On the other hand, why don't you use external HD? They are also relatively cheap, highly portable, fast and easy to copy every once in a while?

  8. #8

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    Re: "small" .tif or large jpeg

    buy yourself a dvd+/- rewriting drive, and burn onto data DVD+/DVD-r's. This will mean you can have much higher quality images than is possible on a CD-r, and it will save space and chance of loss re: spanning.

  9. #9

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    Re: "small" .tif or large jpeg

    Have you tried png format? I've been able to get considerable lossless compression using png.

  10. #10
    not an junior member Janko Belaj's Avatar
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    Re: "small" .tif or large jpeg

    I have had similar challenge few years ago, and I'm happy that I choose the best quality offered in those days. I had to scan and archive really rare breviary (printed and than partially hand colored book from 17th century, size about 10x15cm - 370 illustrations...). First I have made some tests reprinting in 200% and 400% from 24bit and 48bit scans and have found that larger amount of bits wasn't necessary for that purpose. So I went on 24bit scans.
    Than I had to decide scan resolution - not to write some huge story about tests - I scanned with Scitex (Smart?) scanner at resolutions of 1200, 2400, 3600 and 4800... as mentioned above, anything above 2400 was overkill. 2400 ppi scan give option of printing 75x125cm@300dpi. That was enough - at that resolution, 16 A4 pages would be needed to show each original page. Or I could print saint's portraits with the finest detail still not loosing any data.
    I have got files of size about 370 MB. I saved them as 24bit RGB LZW TIFF - about 110 MB - 6 pictures on one CD instead of 2... 64 CDs in total. Than as JPEGs of best quality (about 40 MB each) burned on 22 CDs. And than I have bought one 80GB HD (was expensive in those days) and copied all files (TIFFs and JPEGs and small JPEGs for preview) to it. Today, that archive is still readable from the very 1st copy - date of scan (I'm looking at it now and am surprised how long time ago was that): Jul 11, 1998, 1:15 PM...
    So, I wouldn't go on 48bit and not over 2400 ppi with your job Daniel. just my 2¢...

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