Nidelva river through Trondheim Norway

Nidelva river through Trondheim Norway
by Saaru Lindestokke                

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I'm looking to print a 12' by 5' banner. Got a photo taken with Nikon D600 in RAW format. But because photo needs to be cropped somewhat, after importing it to Illustrator and resizing, the image ends up being somewhere around 50 PPI.

Is this good enough for a banner this big that is going to be viewed from 10 feet or so? Is the pixelation going to be discernible?

PS: Not sure if this is the right place to ask in StackExchange, but it is related to photography somewhat.

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possible duplicate of How do I generate high quality prints with an ink jet printer? – mattdm Aug 14 '13 at 0:04
up vote 4 down vote accepted

I wrote an answer (rather, "article"), some time back that covered human visual acuity and how to derive the necessary PPI in order for the image to appear continuous at a given distance. In that article, I provided a simple formula that allows one to easily derive the necessary PPI, assuming all measures are in inches:

1 / (P * D)

Where:

  • P is the visual acuity constant
    • 0.00029 for 20/20 vision
    • 0.00020 for 20/10 vision
  • D is the viewing distance

Running the numbers for a print viewed at 10 feet for 20/10 vision (which accounts for the very vast majority of potential viewers):

1 / (0.0002 * (10ft * 12 in/ft)) =
1 / (0.0002 * 120in) =
1 / 0.024 =
41.666

A PPI of 50 would definitely be good enough, and would allow some leeway in actual distance. Hope that helps. :)

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1  
Wow thank you for the very detailed and scientific explanation! :) – pixelfreak Aug 13 '13 at 22:57
    
Appologies for the tagged on question, @jrista but I don't full understand the equation. Would image viewed from 5 ft require a resolution of just under 100PPI ? Or something else? Thanks – Phill Healey Sep 9 '15 at 14:35
    
By my calculation: 1/(0.0002 * (5*12)) = 83.33 PPI. Since that usually is not an option, I would say 100PPI, yes. – jrista Sep 11 '15 at 5:41

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