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Archive 2019 · Calculating the Largest Print Size

  
 
rcm123
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p.1 #1 · p.1 #1 · Calculating the Largest Print Size


I am trying to determine the largest size prints (sharp/good quality)that I can expect to have made from images that I have. Several online articles that I read indicated that the maximum size of a print should be calculated by dividing the dimensions of an image (in megapixels) by the DPI to be used by the printer. Also, for the highest quality prints (to be reproduced in a magazine or displayed in a gallery) the megapixel dimensions should be divided by 300 DPI. For good to very good quality prints to be displayed at home, the megapixel dimensions should be divided by 200 to 250 DPI.

However, when I used this approach, I was surprised by the results in that the maximum size of a quality print that could be made from some of my images seemed to be much smaller than I expected. So, I ran the formula on some images that I previously had blown up and printed by a professional printer at 16" X 24." For those images, the formula (even at a "minimum" of 200 DPI) indicated that the largest print was only 10" X 14."

Did I misconstrue the formula for calculating maximum print size? Or, is there some other formula that is better to use? Thanks in advance for any information you may be able to provide.




Oct 03, 2019 at 05:18 PM
rico
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p.1 #2 · p.1 #2 · Calculating the Largest Print Size


I'm happy to use 150 PPI for prints that will withstand close scrutiny. Since my cameras are 24MP (6000x4000 pix^2) I can create 2'x3' prints to this standard. I arrived at 150 MPI by experimenting on my printers (Canon Pro-100, Pro-2000).


Oct 03, 2019 at 06:43 PM
John Wheeler
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p.1 #3 · p.1 #3 · Calculating the Largest Print Size


Hi rcm123

Most of those equations are based on a viewing distance of 10 to 12 inches and only considering the resolution limit of the average eye for distinguishing detail.

If you are viewing at 20 to 24 inches, then the resolving power of the eye is cut in half and using 1/2 the dpi of the formulas would be just fine.

Note that it is normal for one to observe a larger print at the distance of about the diagonal of the print. So an 8x10 viewed at 12 inches is pretty normal and viewing a 16 x 20 print viewing at 24 inches is pretty normal. Large prints can get by with less resolution following that viewing distance rule.

However, the catch is there is always someone wanting to view a large print really close up (the pixel peeper types) and under those circumstances, the print the larger prints would look a bit softer.

So it depends on the viewer and the closest expected viewing distance. Yet this should help expalin why your larger prints were looking just fine, I bet you were looking at the with your eyeball right on top of them.

Hope this helps.



Oct 03, 2019 at 08:06 PM
AcuteShadows
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p.1 #4 · p.1 #4 · Calculating the Largest Print Size


Viewing distance is generally at about diagonal of a print. But for wide angle, maybe you want viewers to be closer to the picture. Or, for a landscape photo, viewers may be interested in the details as well as in the overall pictures. So the resolution you need depends on the picture and the specific circumstances of the presentation of the picture.

Even if you can distinguish colors of individual pixels, your lens, or a moiré filter, or noise reduction, may reduce effective resolution at a specific level of contrast reproduction (i.e. modulation transfer) to a value that is lower than the senser pixel resolution. Therefore you need to evaluate all characteristics of the picture, in addition to the pixel count.



Oct 03, 2019 at 10:53 PM
Imagemaster
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p.1 #5 · p.1 #5 · Calculating the Largest Print Size


There are too many differing viewing factors for there to be any single magic formula.


Oct 03, 2019 at 11:11 PM
rcm123
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p.1 #6 · p.1 #6 · Calculating the Largest Print Size


rico wrote:
I'm happy to use 150 PPI for prints that will withstand close scrutiny. Since my cameras are 24MP (6000x4000 pix^2) I can create 2'x3' prints to this standard. I arrived at 150 MPI by experimenting on my printers (Canon Pro-100, Pro-2000).


Rico, thanks for the info. One question though: while the original images produced by my 5D IV or 1DX II have good dimensions in terms of pixels, I almost always crop the images to some degree in post processing. Am I correct that in calculating possible print sizes I should use the dimensions of the cropped image?



Oct 04, 2019 at 07:20 AM
rcm123
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p.1 #7 · p.1 #7 · Calculating the Largest Print Size


John Wheeler wrote:
Hi rcm123

Most of those equations are based on a viewing distance of 10 to 12 inches and only considering the resolution limit of the average eye for distinguishing detail.

If you are viewing at 20 to 24 inches, then the resolving power of the eye is cut in half and using 1/2 the dpi of the formulas would be just fine.

Note that it is normal for one to observe a larger print at the distance of about the diagonal of the print. So an 8x10 viewed at 12 inches is pretty normal and viewing a 16 x 20 print viewing
...Show more

John, this is very helpful. I actually gave no thought to the expected viewing distance. It makes a huge difference in real life and explains (for me) why my larger prints look so good despite the "formula" predicting that the digital image could only be used for a much smaller print. Thank you, Rich

BTW, even when I look at my larger prints up close, there is no noticeable pixilation.




Oct 04, 2019 at 07:26 AM
rcm123
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p.1 #8 · p.1 #8 · Calculating the Largest Print Size


AcuteShadows wrote:
Viewing distance is generally at about diagonal of a print. But for wide angle, maybe you want viewers to be closer to the picture. Or, for a landscape photo, viewers may be interested in the details as well as in the overall pictures. So the resolution you need depends on the picture and the specific circumstances of the presentation of the picture.

Even if you can distinguish colors of individual pixels, your lens, or a moiré filter, or noise reduction, may reduce effective resolution at a specific level of contrast reproduction (i.e. modulation transfer) to a value that is lower than
...Show more

Acute Shadows, thank you. Your comments about the subject matter/presentation of a picture dovetail with the other posted comments and have helped me form a much better understanding of the whole process.



Oct 04, 2019 at 07:32 AM
rcm123
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p.1 #9 · p.1 #9 · Calculating the Largest Print Size


Imagemaster wrote:
There are too many differing viewing factors for there to be any single magic formula.


Thanks Imagemaster. Based on the other replies to my post I understand your point.



Oct 04, 2019 at 07:35 AM
rdeloe
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p.1 #10 · p.1 #10 · Calculating the Largest Print Size


It's the cropped image that is sent to the printer. So yes, use the dimensions of the cropped image to calculate your desired print size.

There are lots of perspectives on this out there, as you've already seen from the responses. There are also too many variables in play to make one-size fits all answers sensible. Printing the picture and then positioning it where it's going to be is always a good way to decide if you're happy with resolution.


rcm123 wrote:
Rico, thanks for the info. One question though: while the original images produced by my 5D IV or 1DX II have good dimensions in terms of pixels, I almost always crop the images to some degree in post processing. Am I correct that in calculating possible print sizes I should use the dimensions of the cropped image?





Oct 04, 2019 at 07:50 AM
rico
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p.1 #11 · p.1 #11 · Calculating the Largest Print Size


rcm123 wrote:
Am I correct that in calculating possible print sizes I should use the dimensions of the cropped image?


As already mentioned, you calculate with the cropped image. PPI and viewing distance can be condensed to the singular measure of angular resolution. The human eye has limits to resolvable detail, called visual acuity: https://en.wikipedia.org/wiki/Visual_acuity If you view a roadside billboard at 1' then the detail doesn't impress. Inkjet prints are similarly unimpressive when viewed under a microscope—although the dithering pattern is cool.



Oct 04, 2019 at 08:10 AM
mrca
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p.1 #12 · p.1 #12 · Calculating the Largest Print Size


The recommended viewing distance of a painting or photo print is one to 1.5 times the diagonal of the print...unless you are a photographer, then it is the length of your nose. Ever see a painter working then stand back from the canvas. That's to examine it at the proper viewing distance.


Oct 04, 2019 at 10:26 AM
rdeloe
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p.1 #13 · p.1 #13 · Calculating the Largest Print Size


You can treat your prints with sprays that reduce the impact of photographers' noses leaving greasy marks.

mrca wrote:
The recommended viewing distance of a painting or photo print is one to 1.5 times the diagonal of the print...unless you are a photographer, then it is the length of your nose. Ever see a painter working then stand back from the canvas. That's to examine it at the proper viewing distance.





Oct 04, 2019 at 11:49 AM
AcuteShadows
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p.1 #14 · p.1 #14 · Calculating the Largest Print Size


rdeloe wrote:
You can treat your prints with sprays that reduce the impact of photographers' noses leaving greasy marks.



A technique also known as de-nosing.




Oct 04, 2019 at 06:16 PM
EB-1
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p.1 #15 · p.1 #15 · Calculating the Largest Print Size


A print has to exceed my corrected vision at 12" and still look good at 10".

EBH



Oct 04, 2019 at 11:49 PM





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