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I have designed a custom deck of cards and I want to send my designs to print. It took me a few weeks to complete my designs using GIMP. I'm new to digital design and made a mistake – I did not set the DPI for the canvas and my designs are set to 96DPI.

What do I need to do to ensure I get high quality prints?

Here's an outline of my project ad what I've done to this point:

  • The requirements are 822x1122 at 300dpi
  • I did an experiment and the results are confusing to me
  • I took a large image from the internet (1280x1008), opened GIMP with a 300DPI canvas and scaled the image to 500x394 and saved it
  • I opened GIMP with a 96DPI canvas and scaled the same image to
    500x394 and saved it then copied the image from the 96DPI canvas and pasted it into the 300DPI canvas.

I thought the 96DPI image would shrink on the 300DPI canvas however both images appear exactly the same in size and pixelation when zoomed in.

Are these images the same quality?

I could create new 300DPI canvases and paste my 96DPI designs into it but surely the data is already lost, but images scaled to a 300DPI to begin with do not look any better than my 96DPI images.

  • DPI does not impact pixels on a screen (that's why you're not seeing a difference in your test—they're the same). It is simply a way of relating an image on a screen to a printed copy. If you created your graphics at the specifications the client wanted (822 x 1122 pixels), and they require 300 dpi, the only thing that matters is whether or not they want the final print version to be 2.75 inches by 3.75 inches (and they had better). – Geoff Ball Jan 9 '17 at 16:18
  • So if I paste my 96DPI design into a 300DPI canvas will that be fine? I havn't lost quality anywhere? – Ziggletooth Jan 9 '17 at 16:24
  • Just be sure not to send the images at 500x394px - reducing the number of pixels is what removes details of the image. – jsbueno Jan 9 '17 at 16:25
  • That's right. Your client can print your 822x1122 pixel document any size they want. The only size that will get them "300 dpi" is 2.74x3.74 inches. Print larger, and the dpi is less. Print smaller, and the dpi is more. If they knew what they were asking for—and wanted to mention a resolution—they would have asked for the document in a dimension of size (inches, mm, etc.), not pixels. – Geoff Ball Jan 9 '17 at 16:28
  • I understand now, thanks a lot for all your help guys. – Ziggletooth Jan 9 '17 at 16:40
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Any PPI requirement only makes sense if it is accompanied by a physical size, and if you're given a pixel size requirement then the PPI is irrelevant. As long as your pixel dimensions are correct then the PPI doesn't matter.

As I previously said here:

PPI is not an inherent property of an image. There is no such thing as a 300PPI image, or a 72PPI image. PPI is just a useful measurement for determining the print size of an image.

Which means PPI is completely irrelevant unless accompanied by physical dimensions. If someone says "Can we have that image in 300PPI?" they need to tell you a physical size in inches or centimetrs or whatever else, otherwise the question makes no sense.

A 100 × 100 pixel image saved at 300 PPI is exactly the same as a 100 × 100 pixel image saved at 72 PPI, or 10 PPI, or 1 PPI. They are even exactly the same if you print them at the same size.

The only times PPI is a useful measurement are...

  1. You have a physical dimension requirement and you need to know how many pixels you need in your image.

    Say you need a 6 × 4 inch image at 300 PPI, that allows you to calculate how big in pixels your image needs to be. 6 × 4 (inches) times 300 (PPI) is 1800 × 1200 — and there is your required size in pixels.

  2. You have an image at a certain size in pixels, and you want to know how big you can print that image.

    Say you have a 1800 × 1200 pixel image and you want to print it at 300 PPI. 1800 × 1200 (pixels) divided by 300 (PPI) is 6 × 4 — and that is your print size in inches.

  • Lots of good information here, except you never mentioned how to access DPI settings in GIMP (Image > Print size). I think seeing and fiddling with the print size in GIMP can help someone understand what it really means. – Scribblemacher Jan 9 '17 at 16:39
  • 1
    I understand now. Its used to relate pixels to a print size and has nothing to do with some inherent quality of the image. So if I wanted to double the quality I could of made my designs 1644x2244 pixels at 600DPI and that would give me the same physical size as 822x1122 pixels at 300DPI which all relates to 2.74x3.74 inches. Thanks for all your help. – Ziggletooth Jan 9 '17 at 17:07
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TL;DR: don't worry about the image settings for DPI – they are just a number. If you have it at the required number of pixels, everything is going to be fine.

The, often incorrectly required "DPI" – for "Dots per Inch" is only an indicative of how many printing dots per each linear inch your image will have. The number of pixels, on the other hand, is what conveys the actual image information.

To set the DPI on GIMP images, you can simply go to the Image->Print size... dialog box, and type in 300DPI, and see GIMP calculate the physical size the images will be printed at no loss.

See that if you have your image at 822x1122 pixels, and on the same dialog set it to "96DPI", the print size will be calculated to be larger than the physical card.

However, there are other issues at hand: if there is any text or drawings on the line (as opposed to photographic content), do not send them as jpg files – be sure to export your printing files as .png or .tiff.

  • First of all I am extremely impressed by this forum. The relative speed and quality of responses is very impressive. I think I understand how DPI works now, and what was wrong with my thought process. I was worried I would have to find the original assets and redo everything, I am happy that I was wrong. – Ziggletooth Jan 9 '17 at 16:39
  • @Ziggletooth I think part of the unbelievable efficiency comes from the fact that we're not a forum. Off topic answers get deleted, comment trails (like this one) most probably will be deleted too. – Zachiel Jan 9 '17 at 19:28
  • @Ziggletooth Don't forget to mark accept one of the answers if it helped solve your problem. It's the little checkbox to the left of the answer. Welcome to GD.SE! :) – Vicki Jan 9 '17 at 22:43
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Just to complement jsbueno's answer. PPI is just a number except if you really need it.

The point you are missing is that you never, ever, mention a phisical dimension.

The total pixels you have 822x1122 make sense in 300 ppi using this operation:

822/300 = 2.74 inches. 1122/300 = 3.74 inches.

Your cards are measuring 2.74x3.74 inches.

Then the 300 ppi matches the requirements.

If you had not used the total pixels, but the phisical dimensions plus the 96ppi then you were in trouble.

96x2.74= 263 px 96x3.74= 359 px

But you are safe.

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