645 MF in pixel equivalent

Discussion in 'Digital Photography' started by drs, Oct 2, 2004.

  1. drs

    drs Guest

    I just saw an item on the internet that said a 645 medium format
    negative contained 63 megapixels of information. That statement is
    ambiguous at best, isn't it? Wouldn't different sensors have different
    numbers of pixels? But regardless of whether the statement is true,
    how does a 645 negative scanned at 4000 dpi compare to a photo taken
    with a digital slr (not medium format)?
    drs, Oct 2, 2004
    1. Advertisements

  2. Check out:


    Roger N. Clark (change username to rnclark), Oct 2, 2004
    1. Advertisements

  3. drs

    Bill Hilton Guest

    No doubt it's the Gospel Truth, since you never find any misinformation on the
    internet :)
    You can get pretty much any number of pixels you want by scanning at a
    particular scan rez ... with my 645 films and my 4,000 dpi scanner for example
    I get around 56 Mpixels. Scanning at a higher rez with a drum scanner (which
    can scan 11,000 dpi easily) would increase the pixel count, so basically what
    your quote says is you're still plucking out useful info from the film at a
    slightly higher rez than 4,000 dpi, which I would agree with.
    I interpret it to mean you are still scanning info out of film with scan
    resolutions slightly over 4,000 dpi ... the most common figure I've seen is
    that film maxes out at around 5,000 dpi, though some (like Roger) disagree with
    this. At some point you're just scanning grain though and the extra rez isn't
    buying you anything.
    What do you mean by "sensors"? This is film. The number of pixels you end up
    with depends on your scanner rez (unless you interpolate).
    I just shot some aspen photos last week with a Canon 1Ds (11 Mpixel digital), a
    Pentax 645 with Velvia and a Mamiya 6x7 with Velvia, shooting the same scenes
    with comparable lenses so I could answer this question to my own satisfaction.
    I'm going to print a couple of scenes to make this comparison for myself
    tomorrow once I scan the film @ 4,000 dpi. I'm printing 16x20" on an Epson
    4000 and will show the prints around to see what others think too.

    When I've done this test with the 1Ds vs 35 mm film the 1Ds won handily. I've
    already printed a couple of the digital images and they look fine but I suspect
    the scanned medium format film will look a bit better, though not as much
    better as the file sizes indicate. One thing I did notice was the film (on a
    light box) has a wider range of colors (ie, a wider gamut) ... how well this
    will translate onto a print is something I'll see tomorrow I guess once I print
    the film images. You rarely see this discussed and it's not important for many
    types of shots digital is fine for (portraits, most product shots, wildlife),
    but for landscapes I prefer having a wider gamut range to capture subtle
    colors. My money is on the film for this print test (especially the 6x7 cm)
    but we'll see.

    Here's a very controversial site that ran this same test and concluded that the
    1Ds beats medium format film easily. Most people who have run similar tests
    reached the opposite conclusion though, feeling that 11 Mpix is getting close
    to 645 but doesn't quite surpass it ...
    http://www.luminous-landscape.com/reviews/shootout.shtml (this one always
    brings out the loonies :)

    Bill Hilton, Oct 2, 2004
  4. Can't really translate film and digital. Astia can resolve 150 lp/mm but
    what can the lens deliver?
    ~Darrell Larose~, Oct 2, 2004
  5. drs

    Tony Guest

    Tony, Oct 2, 2004
  6. << Can't really translate film and digital. Astia can resolve 150 lp/mm but
    what can the lens deliver? >>

    Darrell et al-

    This brings up another point that I didn't see mentioned here. When you scan a
    negative, you are using an optical process that has another lens. Even if it a
    good one, you still have a resulting digital image with imperfections
    compounded by the imperfections and resolution of two lenses plus a limit
    determined by both the film's grain and the digitizer's sensor matrix.

    In other words, you are kidding yourself if you think it is a fair evaluation
    of medium format film images compared to high-megapixel digital images.

    Fred McKenzie, Oct 2, 2004
  7. Bill,
    Please specify what film you are using. My own tests showed fuji
    velvia was equivalent to about 45 megapixels digital equivalent.
    I believe that with velvia you can get a little more info beyond
    5000 dpi, but it really is diminishing returns. However, grain
    becomes smaller and less noticeable at higher res scans (like
    8,000 dpi).

    Roger N. Clark (change username to rnclark), Oct 2, 2004
  8. This assumption is false because the two optical systems
    (original camera lens and scanner lens) are not necessarily
    similar. For example, a good drum scanner uses microscope
    optics, so can resolve many times more detail than a
    typical camera lens.

    Roger N. Clark (change username to rnclark), Oct 2, 2004
  9. drs

    drs Guest

    On Fri, 01 Oct 2004 18:10:17 -0600, "Roger N. Clark (change username

    Your sites are informative although they're way above my head in terms
    of understanding everything. Thanks for suggesting them. Part of why I posted the note in the first place is I'm trying to
    match what camera equipment I want with what I can afford. Since I
    already use a 645 MF, I was wondering how scanning the negs would
    compare to shots taken with some of the digital slrs that I can't
    afford. Not that high quality scans are cheap but that was behind the
    drs, Oct 2, 2004
  10. Insanely overoptimistic would be a more accurate assessment of that
    16.7MP vs 645: http://www.pbase.com/davidjl/image/34473562/original

    16.7MP vs 35mm: http://www.pbase.com/davidjl/image/34473670/original

    These compare 300D images taken at 22mm and 35mm focal lengths upsampled
    appropriately with a 4000 dpi scan of a Tech Pan frame shot with a Mamiya
    645 + 35/3.5 lens.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Oct 2, 2004
  11. drs

    Bill Hilton Guest

    These two statements seem contradictory to me, if you mean 45 Mpix for 6x4.5 cm
    medium format. 45 Mpix implies a scan rez of about 3,600 dpi or so (I get
    about 55 Mpix at 4,000 dpi) ... you say "you can get a little more info beyond
    5000 dpi" but even 5,000 dpi would mean about 93 Mpixels or more than twice as
    many pixels.

    Can't have it both ways :) If it's really 45 Mpix then the scan rez is well
    below 5,000 dpi, assuming you meant 645 ...

    BTW I got the 5,000 dpi number from Bill Atkinson, often called the "Ansel
    Adams of digital photography". His home scanner is a Tango drum that goes up
    to 12,000 dpi or so and in a class I took with him he said he scanned both MF
    and large format Velvia at various resolutions from 4,000 dpi up to 10,000 dpi
    and decided 5,000 dpi was the point at which he simply didn't see any further
    improvement with LightJet prints.

    Bill Hilton, Oct 2, 2004
  12. drs

    Bill Hilton Guest

    You can get a really nice MF film scanner like the Nikon 9000 for (I think)
    under $2,000. You didn't mention how large you want to print but with this
    setup you'll definitely get better large prints than with digital files from
    the 8 Mpixel dSLR's, based on what we're seeing with our Canon 1D Mark II's.

    Bill Hilton, Oct 2, 2004
  13. drs

    drs Guest

    I haven't printed anything larger than 24 inches wide but those have
    been very clean with the MF. I guess I want the impossible: a digital
    I can afford that will match the detail I like with MF. I'm not
    familiar with the Nikon 9000 but I'd probably put that kind of money
    toward a camera. I keep hoping a dslr with about 15 mp will be
    available for $1500. I'm sure it will but I'd sort of prefer it within
    my lifetime.
    drs, Oct 2, 2004
  14. Yes, you are hoping for the impossible. Maybe, next year. ;-)

    Seriously, if you want MF quality prints from digital, you won't get
    it from any digital camera or MF digital back today, even those $10k
    to $20k, 36mm x 48mm, 22MP ones are really only equivalent to a good
    35mm camera and 100 speed film. For 645 equivalency, you'd need
    around 3 times 22MP, since 645 is a little more than 3 times the area
    of a 35mm film frame. Film still has the edge over digital where
    resolution is concerned. So, a good film scanner and a medium format
    film camera is still the most cost effective solution for now. And
    don't cut corners on the printer either, or you'll have wasted that
    money buying a good camera and film scanner. Your prints will only
    be as good as the weakest link in the workflow.
    Stefan Patric, Oct 3, 2004
  15. I meant that the maximum detail scanned from 645 film would produce
    an image that would require a digital camera with about 30 to 45
    megapixels to match spatial detail. The ~30 megapixels is the luminance
    spatial resolution, and ~45 megapixels is the color spatial detail.
    A 4000 dpi scan of 6x4.5 cm film would give about a
    7000 x9000 pixel image, or 63 megapixels but have somewhat
    less real resolution. A 5000 dpi scan would come close to
    getting all the detail off the film. Of course the film would
    have much less signal to noise than a digital camera image, so
    a much smaller digital image, like Canon's new 16 mpixel camera
    can apparently look as good or perhaps better, but would have
    less actual resolution. I think we've agreed on this
    in the past. It is hard to quantify the increase in perception
    of image quality with signal to noise alone, but it is quite
    I put the number at 6000 dpi personally. For drum scans, I've
    been getting 6000 dpi scans of 35mm velvia which give approximately
    140 megabyte files. I've seen 11,000 dpi drum scans of
    35mm kodachrome 25 enlarged to 30x40 inches that was jaw-dropping
    (I thought it was at least 6x7 medium format).
    I done tests of velvia scanned up to 11,000 dpi,and the
    interesting thing I find is that while no more spatial detail
    gets scanned, the grain pattern appears smaller and less
    apparent in the higher resolution scans (above 6000 dpi)
    (yet another web page on my list to build).
    For 4x5 I've done many ~3300 dpi scans for 650 megabyte files
    (just fits onto a CD). Now, I've gone to 16-bit scans,
    so these file sizes double. My opinion from all these tests
    is that scanners in the 4000 to 5000 dpi range maximize apparent
    grain of fine grained films like velvia.

    Roger N. Clark (change username to rnclark), Oct 3, 2004
  16. I agree. Another thing if you are interested in landscapes and
    use small apertures, like f/16 and smaller: digital cameras
    suffer from dust on the sensor that becomes real apparent
    at small apertures. Thus, you are much better off with film.

    Roger N. Clark (change username to rnclark), Oct 3, 2004
    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.