Printing 60" x 48" Viewing distance vs. DPI

Discussion in 'Digital Darkroom' started by photo_dark, Jul 7, 2008.

  1. I am working on some images and graphics for posters that will be printed at 5' x 4' on heavy banner material. My
    question is, assuming these will be viewed at a distance greater than 5', what is the minimum DPI i would want to
    be using?

    Also, the raw images I am working with are 3888 x 2592. Assuming these are top quality images (sharpness and
    noise, given the resolution) what is the largest print you would consider doing? Note that there is some margin
    for pixelation given the material these will be printed on. Banner material is a lot more forgiving than trying
    to do gallery prints.

    Thanks for any advice or experience lended :)
     
  2. David,

    Being viewed at 5 feet or more, 150 DPI should be plenty, though a 10MP image like you describe, you could probably go to 233
    DPI and still have a nice image, though the file would be a PIG!

    Of course, the best way to determine will be to rez-up the image to the size you want, and print out some sections at 100% on
    your printer to see if it's acceptable to you. When doing enlargements, I get laser prints at 12 x 18. Not only do you get to see a
    larger section, but laser prints are pretty unforgiving, so if it looks clean on a laser, an inkjet on vinyl will probably be just fine. Lasers prints are
    cheap, if you're not happy with it, you're not out much.

    A trick I used to use when blowing up images for clients (usually crappy ones, much smaller than what you have) was to
    resample past what I was printing (say 400 DPI) and run 2-3 pixel "Median" filter, before resampling back down to the final print
    resolution. Keep in mind that this is a VERY slow process, so you should only consider this if you find the noise or pixilation to
    be unacceptable.

    Hope you have lots of scratch disk space!

    Good luck. Let me know how it goes!
     
  3. jumbogiant.com, which is where i get my prints done. wants 150dpi for any work. their sizes go from 8x10 to 40x60 or up 24x80 panoramas.

    the biggest i have had them print is 20x30inches and 12x48panoramas. results great.
     
  4. Excellent advice, Thanks Gary and TM. I'm really too overly worried..... I've just never upsized any of my own images before to this size before, and since the cost can run $500+, I want to make sure they are going to look good! I will definitely take your advice TM and print out some 12x18 crops first, especially around the faces and where there are details to test it.

    On a side note, I have a 7000 x 4000 px landscape stitched image that we will be using that will be upsized to 72"... I am actually quite looking forward to the end result :)

    Anyone have any further tips for me?
     
  5. Back when the Nikon CP 990 was named digital camera of the year, one was used to create a billboard. The billboard
    looked great, at distance, where we all look at billboards. The CP 990 is only a 3.3 MP camera, but it worked very well for
    that billboard.
     
  6. Besides agreeing with what everyone else said... You mention these are being used with images and graphics for posters, that to me implies there may be some text or something else with crisp edges. This usually means you'll need higher resolution than what you would otherwise need for photos. At 150dpi, 60x48 is only 200 MB, which isn't a lot in these days of plentiful memory.

    Also, keep in mind that a blurry image looks better than a pixelated image. Pixelation has got to be my number 1 pet peeve when looking at digital artwork. There's no excuse to have it these days, so up the resolution to whatever is necessary and be careful when upsizing.
     
  7. I print at 40 inches regularly. Every person who looks at my work walks as close as they can to the image (about 7-8
    inches) and looks in there. I believe there is no such thing as "viewing distance".

    I prefer 360 dpi for printing. However, I don't use Chromira, not a shiny paper guy. Using 300 - 3888/300=12.96 - yields a
    13 inch print at 300 dpi. Make that a 26 inch print at 150, a 52 inch print at 75. I wouldn't expect too much.

    lenny

    EigerStudios
     
  8. Yes there will be text, although it will be somewhat small. Here is my typical workflow, any advice would be helpful.

    Export from DPP as 16bit Tiff, ProPhoto RGB, bring into photoshop and do curves adjustments, or any other minor color corrections i'll be doing.

    Convert to 8bit, continue editing process (pushing highlights and shadows, local contrast)

    Upsize to 60" x 48" or 60" x 36" in photoshop at 250dpi (or so, depending)

    Add any text or vector work needed.

    Convert to CMYK, save as 8Bit TIFF, send to printing company.

    You know, it's so much less stress when you're only dealing with 5x7 prints and a replacement is cheap. 5' banners are pricey!
     
  9. Again, stating that I think your image will probably be fine, consider adding any vector based art/text BEFORE rezzing-up the photo.
    Vector objects aren't subject to pixilation the way bitmap art is, and since some degradation in quality is unavoidable, one thing that
    will draw attention to said degradation will be super-clean vector objects. Of course, there are no hard and fast rules; so while it might
    be kind of a pain, I would test it both ways. There could be a little balancing act between obvious clarity differences and "sawblades"
    on the letter "G."

    I once blew up this old photo of Johnny Cash for a friend, who wanted text (that would get this post deleted) on top of it. While not
    great, what really made the photo look bad was the fact that the text was so clean.

    Also, if you absolutely HAVE to go to CMYK (check with your printer; i almost always did LF prints in sRGB), I would do the conversion
    first. I'd like to prevent you from having to do your color corrections all over again, and RGB > CMYK conversions DO often do
    craptacular things to color, most notably it has a tendency to flatten color (blues and greens are a particular problem).

    I guess I just assumed, but don't know...this is a large format Ink jet onto Vinyl? If you have any other specs (namely the printer or RIP)
    let me know.
     
  10. With a 5 percent contrast the a great eye can resolve about 0.47 mm lline pairs at 1 meter. A 5 feet viewing distance is about 0.72 mm line pairs; ie 0.028 inch; ie 35 per inch; ie about 70 ppi . If its a poster on a billboard at 50 feet; then its 7 ppi; a 1/2 foot viewing distance thus is a 700ppi number. Amateurs often print higher; upsize where it doesnt matter for 2 reasons; they dont have goals like a commerical project; or over spec where it doesnt buy you anything. The viewing distance can be rigid in commercial print job; it can be a full wallprint to viewed while in a dentists chair; the chair is bolted to the floor. It might be a image and warning poster for a zoo; one would have to climb over snakes to get closer to the poster. For a giant wall map of a city the ppi/dpi required can be high so street names are readable,.
     

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