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Archive 2013 · Resolution Needed for 18x24 Print
  
 
Ken_K
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p.1 #1 · Resolution Needed for 18x24 Print


A friend called today and wants to have an image printed at 18 x 24". My first question was "What is the resolution of the image"? It was shot at 2278 x 2828 giving 6,487,744 pixels. My gut feeling is that there are not enough pixels to properly print this image at the given size. I'm also guessing that a print this size would probably be printed at 150-200 dpi.
Can someone a) Correct my assumptions and b) Provide a formula or reference to determine the maximum size for this image to look acceptable.
Thanks for your help.



Apr 26, 2013 at 11:13 PM
hugowolf
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p.1 #2 · Resolution Needed for 18x24 Print


Ken_K wrote:
A friend called today and wants to have an image printed at 18 x 24". My first question was "What is the resolution of the image"? It was shot at 2278 x 2828 giving 6,487,744 pixels. My gut feeling is that there are not enough pixels to properly print this image at the given size. I'm also guessing that a print this size would probably be printed at 150-200 dpi.
Can someone a) Correct my assumptions and b) Provide a formula or reference to determine the maximum size for this image to look acceptable.
Thanks for your help.

There is no set formula. It isn't just the input resolution that matters, but also the quality of the pixels and the subject matter. So 120 ppi may work, and depending on expectations, it may not.

It is also probably worth noting that 2278 x 2828 is not the same aspect ratio as 18 x 24 inches, so it will have to be cropped.

Brian A



Apr 26, 2013 at 11:24 PM
Eyeball
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p.1 #3 · Resolution Needed for 18x24 Print


Depends quite a bit on expected viewing distance and the detail in the image. A portrait can probably get by with a little less than a detailed landscape, for example.

Just to give you an idea, here are the PPIs recommended by the late Bruce Fraser based on viewing distance and a viewer with 20/20 vision:

Viewing distance in inches/PPI
8 / 480
10 / 360
12 / 300
18 / 240
24 / 180

I calculated 118 PPI for the most restrictive dimension in your case. I suspect it will look OK but not fantastic as long as viewers aren't going to be close to the print. Doing some careful up-rezzing, perhaps with a package like Perfect Resize from OnOne Software may help a little bit, too, but it won't perform miracles.

I recommend doing a test print of a cropped portion of the image at the final resolution. A 4x6 will only cost a few cents and should give you a decent idea.



Apr 26, 2013 at 11:30 PM
aubsxc
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p.1 #4 · Resolution Needed for 18x24 Print


To obtain an 18" by 24" print at x dots per inch, you would need (18x)*(24x) dots. If you have an image with y pixels, the maximum resolution, in dots per inch, you could obtain (without scaling the image) in an 18*24" print is [y/(18*24)]^0.5, assuming the image has already been cropped to the 3:4 aspect ratio.




Apr 26, 2013 at 11:35 PM
bfs208
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p.1 #5 · Resolution Needed for 18x24 Print


If you print the long side (2828) so that it is 24 inches the other dimension will have to be cropped down to 18 inches from about 19.3. That will print at about 118 ppi which seems pretty borderline for a print that size. If you print at 150 ppi then the long dimension will be almost 19 inches (print would be about 15x19). At that size 150 ppi would probably be acceptable if you don't try to view it from too close a distance. At 200 ppi it will be approximately 11x14. I hope this is helpful.


Apr 26, 2013 at 11:41 PM
Ken_K
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p.1 #6 · Resolution Needed for 18x24 Print


I appreciate all the feedback. It looks like I drew the right conclusion but now I know why
Thanks for "teaching me to fish".



Apr 27, 2013 at 12:47 PM
 

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sbeme
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p.1 #7 · Resolution Needed for 18x24 Print


Of course there is also the issue of how will the image will look uprezzed to something closer to, say 200 ppi at 12x18. Again, much depends on subject, quality of image, viewing distance and subjective acceptability. Portraits, architectural images might uprez very well, for example. Landscapes are a different story unless we are talking long exposure water scenes for example.
What is the subject?
Scott



Apr 28, 2013 at 01:57 AM
Ken_K
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p.1 #8 · Resolution Needed for 18x24 Print


sbeme wrote:
What is the subject?
Scott


I've not seen the image but believe it is a landscape.



Apr 28, 2013 at 02:45 PM
sbeme
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p.1 #9 · Resolution Needed for 18x24 Print


You need to see the image in its largest file size to have a better sense of the ultimate quality of the print.


Apr 29, 2013 at 02:09 AM
Mr Joe
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p.1 #10 · Resolution Needed for 18x24 Print


For reference, you can figure out the resolution of an image in Photoshop by:
Image - Image Size
Uncheck the box that says "Resample Image"
Put in your width and height in inches, and the resolution will be calculated for you.



Apr 29, 2013 at 07:08 PM
smjphoto
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p.1 #11 · Resolution Needed for 18x24 Print


Contrary to the tone of many of these response, I would not hesitate to try a 24" print. I would uprez in photoshop or print out of LR. Both are better at this than we often give them credit. It is important to sharpen after the uprez in photoshop, so that assumes you have access to a file that hasn't been ( over ) sharpened already. I would uprez to a resolution that made my printer happy, 360dpi for epson, 300 for canon.

Most people will be very happy w a large print of an image they like and will not care if it doesn't look perfect at 12", though im not saying this wouldnt produce a perfectly nice print. We get hung up w rules that are overly restrictive. A lot of people believe canvas works well at lower resolutions than paper prints, so that is another possibility.

FWIW, I print large most of the time w 20x30 my normal print. Yes, I prefer large files, but I have lots of older images produced w 6-12 Meg camers, and 16 x24 images are quite good when prepared properly.

I would encourage you to try it before you assume it won't work well. Good luck.
Stuart



May 06, 2013 at 05:09 PM





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