DPI question

I don't know for sure about the phone. I will look at the EXIF. I had received a second email and she said that "this was the original" so the first one must have been either resized or from a text or something. I looked and the data said the phone was a Samsung SM-N96OU

Thanks for those links!

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I see no reason to do any calculations. And there is no need to resize the photo. . That is an image that does not rely AT ALL on resolution of fine detail. . Fine detail has nothing to do with the aesthetic that is in place here.

What, exactly, do you or the photographer think it is in the image that needs to be resolved more than it currently is?

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It is indeed true that a perceived need for 300 ppi in a print is very dependent upon the distance from which a print is viewed...viewed from 10" away might need 300ppi, but if you are standing 40" away from a 20" x 30" print, the limitations of human visual acuity might well make a less number acceptable...the human eye cannot detect anything smaller than one half minute of arc and so smaller pixel size (more pixels per inch) are not detected by the human eye.

At 6 metres or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart, if ihe/she has 20/20 vision (US measurement of visual acuity)...

• 0.875 mm limit at 10',
  
• 0.437 mm limit at 5',
  
• 0.219mm limit at 2.5'
  

The SM-N960U seems to have a 12 mp sensor, so that suggests pixel dimensions of approx 4000 x 3000. If you print to 16x20", that gives 200 dpi. That is not a bad dpi for most photos.

Cropping/resizing during post-processing could have changed the dimensions.

You do need to pay some attention to the shape ("aspect ratio") of the file and the print. They should match. If they don't, as Wilt mentions, the print shop will make some decisions, and they might not be what the customer wants.

(Aspect ratio is width divided by height. So for a 16x20, it would be 1.25.)

Tom, I think the question was when she went to submit the photo to a service for printing, they sent an email back to her regarding the 300 dpi sizing

duckster wrote in post #19085124
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Tom, I think the question was when she went to submit the photo to a service for printing, they sent an email back to her regarding the 300 dpi sizing
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Yes, of course, but those are messages that should be disregarded, because they are sent by default, any time an image does not meet certain pixel counts. . There is no one looking at the images to see if they are images that rely on detail resolution or not.

A lot of people seem to be applying objective answers to a situation that is completely aesthetic in nature, and therefore subjective according to what type of look and feel each particular image has. . Each photo should have its own answer about pixel dimensions and resolution, because each image has different subject matter and each image's strength relies on showcasing that subject matter in a different way.

When someone "does math" to arrive at various pixel requirements, they are often not taking into consideration the very things that matter. . They would use the same math for an image of a foggy ethereal landscape as they would for a close-up portrait of a bird with a complex plumage pattern ...... which of course is a preposterous and wrong thing to do.

The look, mood, and feel of an image should also be taken into consideration when one decides what medium to have the image printed upon. . Metal is a horrid choice for some images, but a splendid choice for others. . Ditto for paper and canvas. . All choices should be made with one particular image in mind, so that the final output is the thing that will showcase that image to the greatest advantage and express the look and feel that the photographer was going for when they took the photo in the first place.


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duckster wrote in post #19085124
Tom, I think the question was when she went to submit the photo to a service for printing, they sent an email back to her regarding the 300 dpi sizing

Most services want to get the file size which permits 300 pixels per inch on the final requested print size, as they understand that the unknowing client might ask for a 20 x 30" enlargment, that only has the equivalent of 75 pixels per inch on the final print...because what is supplied to the lab is a file 1500 x 2250. And when client gets a 20" x 30" print back they stand only 10" away from it and complain about how pixelly it is...Yet the lab gave back the best they could do with the small file submitted by the client to them! So they caution about 300 ppi minimum requirement as a means to avoid such unknowing client complaints!

Excellent point.

duckster wrote in post #19085124
Tom, I think the question was when she went to submit the photo to a service for printing, they sent an email back to her regarding the 300 dpi sizing

If you want I would be happy to resize and sharpen the image in PS as I normally would for one of my metal prints.

That would be great. I would appreciate that

duckster wrote in post #19085503
That would be great. I would appreciate that

I sent you a pm.

Got it. Thanks.