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Thread: Scanning DPI

  1. #1

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    Arrow Scanning DPI

    I have a Epson 4990 for scanning my 4x5 negatives. I wondered regarding dpi how high should you go for the best quality prints for the biggest size prints. I mean it can go to 12800 dpi and produce a 16gb file but surely there is an over kill point?

    Cheers,
    Jamie

  2. #2
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    Re: Scanning DPI

    Quote Originally Posted by jamiek View Post
    I have a Epson 4990 for scanning my 4x5 negatives. I wondered regarding dpi how high should you go for the best quality prints for the biggest size prints. I mean it can go to 12800 dpi and produce a 16gb file but surely there is an over kill point?

    Cheers,
    Jamie
    Tests have shown (confirmed by my own experience) that these and the V700/750 scanners do not gather up any more detail than about 2000-2400 pixels/inch.

    I scan at 2400 just because my computer needs the breathing room. I have scanned medium-format films at 3200 and then downsampled, but I haven't been able to detect any advantage to doing so.

    One problem I have not yet licked is that the scanner seems to posterize the tone curve to some extent, though I haven't yet done enough with color in that scanner to figure out why.

    Rick "still getting used to the V750" Denney

  3. #3

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    Re: Scanning DPI

    I have a 4990 and scan at 2400. As Rick points out, anything more, just gives you bigger files, with redundant pixels.

    One way to optimize resolution with these scanners is to find the point of sharpest focus, just above the glass. If you search this forum, you'll find lots of discussion of film holders from BetterScanning.com, as well as making do-it-yourself holders.

    One way to get more detail and fidelity - without purchasing either a high-end scanner or the services of a scanning service - is to move from 4x5 to 5x7. You get an immediate boost of 66%, and keep your affordable scanner. An 11x14 from a 5x7 is only a 2X enlargement: any scanner can handle that. With larger film, you'll probably never worry about scanner resolution again.

    If you only plan to make images as large as 16x20 from 4x5, these Epsons will be good enough to please all viewers except the most demanding Large Format shooters. Many of them, frequent this forum

  4. #4

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    Re: Scanning DPI

    Quote Originally Posted by rdenney View Post
    Tests have shown (confirmed by my own experience) that these and the V700/750 scanners do not gather up any more detail than about 2000-2400 pixels/inch.

    I scan at 2400 just because my computer needs the breathing room. I have scanned medium-format films at 3200 and then downsampled, but I haven't been able to detect any advantage to doing so.

    One problem I have not yet licked is that the scanner seems to posterize the tone curve to some extent, though I haven't yet done enough with color in that scanner to figure out why.

    Rick "still getting used to the V750" Denney
    That may be about the optical limit of the 4990, and as long as all the edges in your photograph are vertical or horizontal and land exactly on pixels, thats all you should scan at.

    If thats not the case you may find you experience less aliasing and retain more fine detail at higher resolutions.

    My tests with my 4990 show noticable improvments when scanning at 3200 dpi and VERY slight improvements over that at 4800.

    However, I'm wet mounting with a hybrid betterscanning/scanscience solution which does improve the optical limits of my system so that influences my results to some degree.

    Your best bet for determining the resolution YOU should scan at would be to scan several small swatches of the a few images, each at varying resolution, and compare them all at 100%.

    Scan at the lowest resolution in which you can discern additional detail over the next lowest setting.

    (That is assuming your system can handle the image generated. Scanning at a higher resolution and downsampling introduces a level of interpolation that may actually reduce details.)

  5. #5

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    Re: Scanning DPI

    Thanks for the replies I had a feeling it was around 2400.

    The Epson software is bugged... I try to scan any bigger than 2400 I get a message saying "scanner could not allocate required memory" although I have 200GB worth of free space in my temp drive.

    When I try and scan in SilverFast at these high dpi levels there i no problem.. weird.

  6. #6

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    Re: Scanning DPI

    How much RAM do you have ? What operating system ? Are you scanning b&w or color ? 16-bit, 48-bit ?

    Have you cropped the image before scanning ? If you're trying to scan something the size of the bed at high color depth, perhaps you really are running out of room somewhere.

  7. #7

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    Re: Scanning DPI

    Well Ken I don't see how as the same settings in SilverFast work fine :S

    4GB of RAM, on 32 bit system though so 3GB effective. Running Windows XP. Sanning B&W at 16bit.

    I am cropping the image from the preview scan also.

    Might try and older version of the Epson software :/

  8. #8
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    Re: Scanning DPI

    Quote Originally Posted by jamiek View Post
    4GB of RAM, on 32 bit system though so 3GB effective. Running Windows XP. Sanning B&W at 16bit.
    That's exactly how I'm scanning black and white 4x5 negatives, though I'm scanning at 2400. My system is less capable than yours--I only have 2G ram and the system is now 9 years old and running XP-Home without above 175,000 patches. I have been using VueScan, because I have two scanners on the same system and prefer to use one piece of software to operate them both. The version of Silverfast that came with my V750 will only operate the V750, not also my Nikon film scanner.

    Rick "whose stock holders seem to be well focused and who has not yet experimented with wet mounting" Denney

  9. #9

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    Re: Scanning DPI

    Well tomorrow I shall dry a back dated version of the Epson software. Im not the keen on the SilverFast it seems to produce weird results when selecting the options in negafix, like the film and type. The image looks better when I select the wrong film yet Epson software is automatic and produces a lot better image than of SilverFast (tones, levels). So need a fix for the memory problem :/

  10. #10

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    Re: Scanning DPI

    Try VueScan. It should work without problems.

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