Resolution for scanning slides?

Discussion in 'Digital Photography' started by Anthony Buckland, Feb 23, 2005.

  1. Just got my first scanner capable of scanning slides, and I'm
    wondering, what resolution should I use for scanning slides
    so as to neither lose data nor waste memory. Any thoughts?
    Thanks for any replies.
     
    Anthony Buckland, Feb 23, 2005
    #1
    1. Advertisements

  2. Anthony Buckland

    Rudy Benner Guest

    Can't do both. I would go for maximum resolution, then burn the images to
    CDs.
     
    Rudy Benner, Feb 23, 2005
    #2
    1. Advertisements

  3. Anthony Buckland

    drwxr-xr-x Guest

    Gee, it occured to me that this might be an FAQ.
    Therefore, I went to the largest FAQ repository on the
    web with your _exact_ Subject:

    http://groups.google.co.uk/groups?as_q=Resolution for scanning slides

    Learn to fish.
     
    drwxr-xr-x, Feb 23, 2005
    #3
  4. Anthony Buckland commented courteously ...
    Hi, Anthony.

    My limited experience with neg/slide scanning for 35mm
    worked best with a minimum DPI of 1800, preferably 2500.

    This will give image sizes from 2000 x 1600 to maybe 2700
    x 2200. That's pretty large, of course, and whether you
    need to go to 2500 or not depends a lot on the condition
    of your slides, e.g., exposure, film grain,
    sharpness/detail from your camera and developer, etc.

    Then, after post-processing to taste, reduce to the
    finish size you'd like and save to your favorite format.
    The finish size you choose depends heavily on if you want
    to just display your digitized scans on-screen or print
    them at as high quality as possible, or both.

    Err on the side of larger; you can always reduce in steps
    but it is impossible to significantly enlarge without
    loss of image quality.
     
    All Things Mopar, Feb 23, 2005
    #4
  5. Thanks, just the information I needed. To answer your second-last
    paragraph,
    I'll want to do both, a slide slow on a monitor, with printing of selected
    slides, probably no larger than 4x6. The camera was fairly good for its
    time,
    so it sounds as though 2400 would be a good place to start experimenting.
     
    Anthony Buckland, Feb 24, 2005
    #5
  6. Anthony Buckland

    Ron Hunter Guest

    Go here for information on scanning.
    www.scantips.com

    Everything you need to know about scanning.
    And more.
     
    Ron Hunter, Feb 24, 2005
    #6
  7. Anthony Buckland commented courteously ...
    Anthony, prevailing wisdom says you need about 200 PPI
    (pixels per inch) to get a "quality" print, better still
    the closer you get to 300 PPI. There're times when I
    severely violate that "rule", because I just can't get
    near that much PPI with "real" image information (e.g.,
    scanning a snapshot, where you max out at 200-300, even
    then, they're often soft, that's why scanning negs/slides
    is superior to scanning prints).

    But, if you took "200 min, 300 preferably" "rule" to get
    "good" 4 x 6 prints, you'd need in the range of *only*
    1200 x 800 to *maybe* 1800 x 1200. *Much* smaller than
    what you would scan at.

    Still, I recommend scanner at the higher DPI to get the
    best of the detail in the slide, plus while some may
    argue, its been my experience that scanning to 2500
    pixels, then resizing down to 1280 in two steps (with
    mild noise reduction and mild sharpening at the
    intermediate re-size), will yield excellent results. This
    is because the noise generated by film grain tends to be
    "compressed" out (in layman's terms), so you don't have
    apply much if any noise reduction.

    So, again assuming that there's sufficient detail in your
    slides, and you're saying that the camera was "fairly
    good", that leaves only the quality of your slide
    chemical processing (and the speed of the film, higher =
    more grain = scanner noise).

    So, if you think your printing needs will generally be 4
    x 6, you'd probably be OK with my "standard", 1280 x 900
    or there abouts. You could still print on your inkjet on
    glossy 8.5 x 11 paper, just view the prints at a distance
    of 2-3 feet and they'll look superb.
     
    All Things Mopar, Feb 24, 2005
    #7
  8. Depends on what you want to do with the scanned images. If you are going
    to see them only on the PC screen or project with a standard projector, a
    resolution of 720 or 900 (allowing for some cropping during processing)
    will be adequate. No much benefit for any higher resolution (i.e.,
    increasing the pixel count) as the viewing software would reduce the pixel
    count to fit the screen. Some slides you may like to scan at a higher
    resolution if you wish to crop out a large section of the image.

    For printing, higher the better.
     
    Gautam Majumdar, Feb 24, 2005
    #8
  9. Anthony Buckland

    gsum Guest

    You don't seem to understand what this NG is for. Try to keep a civil
    tongue in your head.

    The answer to the question is that it depends on the resolution of the film.
    Provia 100 needs about 2400 ppi, for example. Beyond that, you just
    get a better view of grain.

    Graham
     
    gsum, Feb 24, 2005
    #9
  10. Also, if you are not going to be doing any editing, saving the files as
    JPEG is probably okay. Better to use high res and JPEG than low res and
    non-lossy file format.
     
    Don Stauffer in Minneapolis, Feb 24, 2005
    #10
  11. Thanks for all the informative and helpful replies!
     
    Anthony Buckland, Feb 24, 2005
    #11
  12. Anthony Buckland

    Frank ess Guest

    And, two other considerations:

    Storage Is Cheap. If the slides are at all valuable to you, it is worth
    preserving even the enlarged grain;

    You're more likely to be prepared for Advanced Technology as it evolves,
    if you have bigger images (no telling when _that_ software will emerge;
    I mean the one that looks at your Big Slide File and generates a
    life-size hologram of your beloved pet naked mole rat).
     
    Frank ess, Feb 24, 2005
    #12
  13. Are you using a flatbed or dedicated film scanner?

    I've got a 4K dpi film scanner and generaly scan everything at maximum
    resolution and maximum color depth. I then open the scan in an image
    editor and give it a look at 100% or 200% real size. If the image is
    soft (SLow shutter without tripod, slightly out of focus, subject moved,
    photographer was drunk, etc.) I'll resample it to a lower resolution.
    I'll then do any neccessary color/brightness corrections by comparing
    the image to the slide as it sits on a lightbox. Next, reduce the bit
    depth to 24bit. Save as compressed TIFF and call it done.

    IMO, 2000 dpi will be enough for most casual photographs. Even this is
    too much for some P/S cameras, particularly when using faster print
    films. Saving at usually 4000dpi makes sense only for slow slide films
    that have been shot with a good lens.

    If using a flatbed, forget alleged output DPI and scan at 2000 dpi or
    less. While the scanner mfg. may brag about 4000+ dpi output, the
    optics are seldom better than 1500~2000. Find a good sharp negative and
    try scanning at increasing resolution. You'll reach a point where extra
    dpi does not yield any gain in resolution or detail. Stop there.


    -Greg
     
    Greg Campbell, Feb 24, 2005
    #13
  14. Thanks. I've now tried a few resolutions, and think I'll need to settle
    on about 600dpi. At 2400
    on my (5-year old Win98SE, 256 MBy, 1 GHz) machine, delivering the scan
    to a file takes a
    fair while, but _opening_ the file for editing, etc., takes forever and
    practically flattens the
    machine :(
     
    Anthony Buckland, Feb 26, 2005
    #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.