Is a 4992 X 2474 pixel photo big enough to print a 20 by 30?

Discussion in 'Digital Photography' started by ieani, Jul 31, 2007.

  1. ieani macrumors 6502a

    ieani

    Joined:
    Jan 3, 2006
    Location:
    the states for now
    #1
    According to Shutterfly and York Photo I can but has anyone tried this? If so, what is the quality like? I was told by the photographer that a 16 by 8 would be as large as Id want to go. But I would really like a poster version.
     
  2. seenew macrumors 68000

    seenew

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    Dec 1, 2005
    Location:
    Brooklyn
    #2
    I printed a 2448 x 3264 image (scaled up) at 16x20 and it looked fine. I don't now if this helps, but people told me it wouldn't work, and I think it looks good. I sharpened it a bit when I upscaled it.
     
  3. OreoCookie macrumors 68030

    Joined:
    Apr 14, 2001
    Location:
    Sendai, Japan
    #3
    Yes, of course. The reason is two-fold: first of all, the average viewing distance is rather large, so -- as with billboards -- you don't notice any potential artefacts.

    The second reason is that the resolution of large prints is actually lower, too. Smaller prints (up to 30x45 cm in my lab of choice) are printed with 300 dpi, hence the photographer's recommendation (8 inches x 300 dpi = 2400 pixel). Larger prints are usually made with inkjets at 720 or 1440 dpi. Now this seems larger, but unlike dye-sublimation printers where 1 pixel can take all 16 million colors, colors have to be dithered. Hence 720 dpi effectively correspond to about 150 dpi. 150 dpi x 20 inches = 3000 pixel. Even at 1440 dpi, you will still be ok.

    You should be fine. (Again, you might notice artefacts when you stand right in front of the print and look for them, but practically, it doesn't matter.)
     
  4. Mike Teezie macrumors 68020

    Mike Teezie

    Joined:
    Nov 20, 2002
    #4
    Absolutely. I've had many several 20x30s printed with files from my 5D, and they all looked great.
     
  5. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #5
    Running it out as is to those dimensions would give an effective resolution of approx 166 ppi. And that in itself sounds pretty coarse.

    However, for a print that size you tend not to look as closely as it as if it were an 8' x 10'... it's poster-size so you might typically view it from a few feet away or across the room.

    As the previous poster said, upsampling it and some slight unsharp masking might help. However, depending on the image quality, it's probably best to upsample in small increments in 16-bit to avoid posterisation in certain areas, 2-5% at a time, until you get to your desired size. You can do that with a repeating action in Pshop... Then you can convert it back to 8-bit for printing.

    At that size and viewing distance, 180-225ppi would probably be fine.
     
  6. oscuh macrumors 6502

    Joined:
    Apr 27, 2007
    Location:
    Michigan
    #6
    A good rule of thumb based on a CMYK image is to take the base x height of the finished piece, and divide by 35. In the case of a 20x30, that is 17.15, meaning your image size in CMYK mode, should be at least 17.15 MB. Bigger won't hurt, but that is a minimum size to be sure you have enough resolution.

    Based on the dimensions you're giving with your current image, the CMYK actual size should be approximately 47 MB ... PLENTY big enough.
     
  7. ieani thread starter macrumors 6502a

    ieani

    Joined:
    Jan 3, 2006
    Location:
    the states for now
    #8

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