scanners and file size

Discussion in 'Scanners' started by nobody nowhere, May 25, 2004.

  1. went to a pro shop, which hires equipment for scanning in the shop
    itself. I watched two pros scanning some medium format and large format
    slides with an Imacon scanner. The pictures appeared on a 22 inch Lacie
    Electron Blue monitor, and they took my breath away. But now comes
    the anticlimax: when I asked the size of the file, the medium format
    chap said it was 89MB, and the 4 X 5 chap said that it was ... 30MB! My
    Nikon 8000 produces a file of 430MB or so for a 6 x 6 slide (at 14 bit).
    Allowing for the fact that the pros slides were very much better than my
    normal output to start with (shot in a studio, etc), what could be the
    explanation for the stunning results? Was it the Imacon scanner (after
    all, a flat bed one)? Or I simply do not need files of the size I am
    getting? Yet there is a large school of thought in this NG that one
    should scan at maximum - in my case 4000ppi, and 14 bit! It looks like
    not all pixels have been created equal, and or that size does not matter
    that much. Any comments?
     
    nobody nowhere, May 25, 2004
    #1
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  2. nobody nowhere

    Fuzzy Logic Guest

    You need to scan for the device you wish to output to. There is not point in
    scanning at 4000ppi if the only output device will be a computer monitor (~
    75dpi). Here is an excellent web site that hopefully will get you sorted
    out:

    www.scantips.com

    In particular Scanning 101
     
    Fuzzy Logic, May 25, 2004
    #2
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  3. The Imacon scanners have a reputation for being near-drum-quality, so
    they're definitely among the very best. My guess is that those guys
    weren't working at maximum quality; they were scanning to a particular
    directed filesize (that's how I *order* professional scans), which was
    presumably chosen to be adequate for the intended purpose.

    I suspect the stunning results were largely due to the good lighting
    on the original subjects.
     
    David Dyer-Bennet, May 26, 2004
    #3
  4. nobody nowhere

    Tom Monego Guest


    8x10 x360ppi= 29.7mb
    13x19 x360ppi= 90mb

    Seems clear what they were doing. Scanning to output size.

    Tom
     
    Tom Monego, May 26, 2004
    #4
  5. Why didn't I think of that (no comments please!). They could have
    scanned at full numbers, and then downsampled to output size. Which
    would be better?
     
    nobody nowhere, May 26, 2004
    #5
  6. nobody nowhere

    cc0112453 Guest

    I can't go into all of the technical jargon but it was explained to me by a
    guy who runs a digital photo lab that does everything from shooting the
    pictures, processing them and scanning old film. He said that 35 mm film
    has a grain to it and if you match the pixel size to the grain size, you
    have the optimum resolution for scanning that image. His opinion was that
    if you go any finer all you are doing is putting more pixels inside of a
    piece of grain. Think of a piece of grain as a circle. If you want to
    reproduce that circle all you need is another circle of the same size, not
    twenty little circles. You don't get any better resolution if you scan at a
    higher resolution because the picture or film itself doesn't have any more
    resolution to offer once you have gotten down to one pixel per one grain.
    You can certainly go to four or fifty pixels per grain but then what are you
    accomplishing? You are simply taking a finer picture of a piece of grain.
    It doesn't improve the over all picture quality. Unfortunately I can't
    remember what he suggested as a reasonable resolution to scan at but I'm
    sure it varies slightly. I would suggest starting at 300, make some
    progressive sample scans and compare them. When you can no longer tell the
    difference, that is the resolution you want. Also remember that the higher
    resolution you scan at the bigger your files get. Another thing to consider
    is that if you are blowing up a photo, a poster is not viewed close up.
    Most people think that because they are blowing up a photo that they need a
    huge amount of resolution. That would be true if you were viewing the
    poster from two feet but on the average you look at a poster from at least
    five or six feet away and more like eight or ten. I have a 24"x72" poster
    in my office that if you took it down and inspected it you would think it
    was crap. Looking at it hung on the wall it is stunningly clear.

    Doug
     
    cc0112453, May 30, 2004
    #6
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