Resolution vs physical dimension confusion

[Beth23082061er6k]

Our customers submit print-ready files to us and with one in particular we've noticed that the resoulution is high, but the physical dimensions of the file are quite small. For instance, their recent png file shows dimensions in inches as 0.789 x 1 with a resolution of 2850 ppi. Our actual print size is 7.5 x 10.5 inches. We can downsample the file to 300ppi and our preferred dimensions and it seems to print fine, but we are trying to determine what the customer is doing on their end to have it come out this way and if we should have them do something different. We believe they are using Photoshop to create their art. The relationship between resolution and dimensions has always been a point of confusion for me, so hoping someone here can help clarify and explain what is going on and if we or the customer need to do something different. Thanks!

[D Fosse]

It's very simple.

The file is just pixels. It has no size.

The size is determined by the pixels per inch number assigned. Pixels per inch means exactly what it says.

[Lumigraphics]

Why are customers sending png files for printing? This is why page layout apps and Postscript were developed, to be resolution-independent.

I assume you aren't a real printer, since imagesetters and digital presses and RIPs can handle much higher than 300ppi artwork.

And never downsample. Just convert to the correct print size while keeping all the pixels.

[Beth23082061er6k]

Why do customers do anything? I wasn't sure why they were sending us pngs for print either. A coworker was just confused about the small physical dimensions displayed in Photoshop and I was trying to find an answer for them as to what the customer could be doing on their end. While our RIPS can certainly handle the higher resolutions, our work is almost exclusively newsprint so not really necessary. 

[Stephen_A_Marsh]

Possibly no need to resample...

In image size, uncheck resample and change the physical print size. The effective resolution will then be calculated and displayed.

PNG files created using export or save for web are stripped of resolution information. PNG files created using save retain their resolution info.

[Beth23082061er6k]

I believe that we did resize them to our print size.. I don't know if the end user used the resample option or not, but I will let them know to uncheck resample moving forward. We were just trying to determine what the customer did to have it be the dimensions it was. If they are doing something incorrectly, we want to work with them to avoid issues in the future. If we are doing something wrong then we need to alter our workflow. 

[Stephen_A_Marsh]

I believe that we did resize them to our print size.. I don't know if the end user used the resample option or not, but I will let them know to uncheck resample moving forward. 

By @Beth23082061er6k

That is step 1, determine if there are sufficient or insufficient pixels for a good quality print at the desired print dimensions.

If there are insufficient pixels, notify the client.

If there are sufficient pixels, are there way too many? Then you may feel the need to downsample, but then one has to be careful that the interpolation does not produce unwanted artefacts that were not in the original (i.e. beware fine repeating patterns).

[Nancy OShea]

the resoulution is high, but the physical dimensions of the file are quite small.

By @Beth23082061er6k

=======

Maybe the image was enhanced from a low-res thumbnail.  There are several AI upscalers available. Some are better than others.

https://www.elegantthemes.com/blog/design/best-ai-image-upscalers#1-gigapixel-ai

[Beth23082061er6k]

Hadn't considered that as possibility...

[Conrad C · Accepted solution]

…the resoulution is high, but the physical dimensions of the file are quite small…their recent png file shows dimensions in inches as 0.789 x 1 with a resolution of 2850 ppi. Our actual print size is 7.5 x 10.5 inches.…we are trying to determine what the customer is doing on their end to have it come out this way and if we should have them do something different.

By @Beth23082061er6k

It turns out that 0.789 inches at 2850 ppi is the same number of pixels as 7.5 inches at 300 ppi. So when that 0.789 inch image is sized to 7.5 inches long without having to resample, it ends up at about 300 ppi, as shown in the demo below.

The length does not meet the requirement, it’s 9.5 inches long and not 10 inches long. That can happen if the original image has a different aspect ratio than 7.5 x 10.5.

I’m not sure how they ended up there. However, it’s very easy for someone to get it wrong if they don’t have a full understanding of how pixel dimensions, real world inches, and ppi actually interact. One way to ensure they get it right every time is to teach them this simple technique, shown in the demo below:

1. Select the Crop tool.

2. In the options bar, choose W x H x Resolution from the first menu. This will lock the Crop tool result to the exact specifications that are about to be entered.

3. Enter the intended print dimensions and resolution: 10.5 in, 7.5 in, 300 ppi.

4. Make any crop adjustments needed, and apply the crop. (You can apply the crop by clicking the check mark in the options bar, the Done button in the new Contextual Task Bar which is what I show, or press the Enter/Return key.)

At the end, you can see that the dimensions can be confirmed in the status bar at the bottom of the Photoshop document, if the status bar is set to display Document Dimensions. And then Image Size is opened to show it is also correct there.

Why use the crop tool? Well, I noticed that if the original is the standard 3:2 aspect ratio image common in digital camera sensors, 10.5 x 7.5 inches is a different and narrower aspect ratio. This requires cutting off the ends of a 3:2 aspect ratio image, so the Crop tool can be used to compose within the final aspect ratio that has to result from the W x H x ppi values entered in the options bar.

[Beth23082061er6k]

I normally use the crop tool as you described when I resize images in Photoshop. I feel like others who have replied here are correct in that they are probably using the Export option rather than sizing the file correctly from the get go and then we end up with the odd dimensions. Some customers tend to forgo using page layout programs to design their ads for us and use Illustrator or Photoshop instead and then try to export their entire ad as a graphic. Our trim size is an odd size too and most people are designing for 8-1/2x11 so their bleeds are off too when they do this. 

[Lumigraphics]

So you charge extra to fix their files.

I used to work for a commercial print where the owner offered "free typesetting" which in practice meant that we sometimes had to recreate customer files from scratch. Business decision I guess.