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I've mainly used Photoshop before and only just picked up Illustrator a few days ago. Anyway, I used Illustrator to create lots of images (with transparent backgrounds) of different letters, each one filled with circles. More to the point, upon exporting as a .PNG, I noticed a resolution option. Me being the little derp that I am, I figured a larger resolution is always better, so I set this to high (300 ppi).

Upon importing the images into my project however, I realized that the images had become a lot larger than they should be. Upon tweaking the export resolution setting, I noticed that if I set this to low (72 ppi), the images come out as the expected size. I was just wondering how I should expect this to effect my drawings. If I were to keep the high resolution images I exported at 300 ppi, am I always going to be forced to reduce their size afterwards by a certain amount? Otherwise, should I always stick to 72 ppi in order to keep the size of the image the same and to avoid needing to re-size things later?

Image quality is not so important in this case, so there probably isn't much reason for me to use anything higher than 72 ppi anyway. Just for the sake of learning however, I thought this would be a good question to ask.

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72 dpi is a screen resolution 300/240 dpi is a print resolution. neither has anything to do with physical size, it's actually how many pixels you get within that size. That's the general rule. Regarding your drawings - what do you mean size? Are your art boards planned in pixels or mm's? What do you do with them? Use them online or print them?

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  • Actually 72 ppi is an historical "screen resolution" and 300 ppi is a standard print resolution, but it can change depending on the printing system. And although we sometimes make the same mistake, dpi is not the same as ppi. :o)
    – Rafael
    Commented Feb 25, 2015 at 11:00
  • I'm always using pixels as measurement. Strangely, when I save a image as 72 ppi, and then open it using Windows Photo Viewer, it is much smaller than a image saved as 300 ppi. Opening either on Photoshop leads to the same effect, where the 72 ppi image is much smaller than the 300 ppi one. If I were to open either on Illustrator however, they are both the same size.
    – JimmyK
    Commented Feb 25, 2015 at 11:02
  • Jimmy, they are not the same size. If you print them they will be the same size but with different quality. Naty stated that on screen it has nothing to do with phisical size. In this case you say you are working with pixel units, but when you export you are changing that value again. Export as the same resolution settings, in this case I feel that 72 is the correct one.
    – Rafael
    Commented Feb 25, 2015 at 11:11
  • Rafael - you are talking about retina displays with 144 dpi, or 150% magnification. So unless you're using a Mac with retina display or designing for iphone/ipad 72 dpi is screen resolution. Jimmy - The reason photoshop opens it smaller or bigger is because as a design software, it allows you to edit every single pixel in the file, so obviously if it has more pixels you will see them all. Try viewing the 100% size of the document - ctrl/cmnd + 1
    – Naty
    Commented Feb 25, 2015 at 11:31
  • philosophical question: you have two displays, both 1920x1080. Both have a 72 (or 96) dpi "screen resolution" as presumed and reported by the OS. One is 13" diagonal, one is 30" inch diagonal. Do they have the same resolution?
    – Yorik
    Commented Feb 25, 2015 at 16:01
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You need to define what is "your project".

The main 2 projects are printed ones and electronic media.

If you are printing, work with phisical mesurements, and at the end you just export at 300ppi. (Or just leave it as vector format) But I'm almost sure that is not your case.

For electronic usage the ppi dosen't matter at all. Look for the pixel values. You need lets say an icon 128x128px, or a background 1920x500px.

If you are preparing icons for a web aplication you probably can use a vector based format like svg. That will keep the image resolution idependent. Another way to do it is to export them to a font based format.

But, again, first you need to define what is your project.

Edited. In this case 72 ppi gives the same pixel size as the declared pixel size on my drawing. If you change the value to 300 ppi the program is re interpreting the size, transforming from 72ppi to inches and then again to 300ppi. So basicly just use 72ppi.

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  • Sorry by project, I just meant a Visual Studio WPF Application.
    – JimmyK
    Commented Feb 25, 2015 at 11:19
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Illustrator has really no pixel unit, what ot does is it equates pixels with points. Sine a point is 1/72 th of an inch you get one pixel is one pixel with 72 ppi export. Otherwise illustrator will just assume your image in inches and act accordingly.

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