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I just placed a large image (6016x4016px) into my illustrator doc.

Artboard is 3000x3000px, and both the illustrator doc and my placed image are 150ppi. However, when I check out the image's info in the links panel, it says it is scaled at 100%. After clicking on the image, the toolbar tells me that it's only at 2887x1927px!

Why does it say scale is at 100% when my image is clearly not scaled to it's full size?

enter image description here

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Ok, you are tripping on the consequence of demanding that a pixel is a unit. Everything you see is entirely correct. Your image is scaled to full size.

So in order to facilitate that people can design in pixels and physical units there are three options:

  • Decide that a pixel has a fixed size.

    This is what adobe has done, this is also what the SVG comitee has done etc. This has certain drawbacks but is essentially the easiest option for a vector application. It also has the easiest perks.

  • Let user define pixel size in relation to units.

    This is what is done in raster applications. However raster applications have the luxury of having only one size. This wouldn't solve your issue since you can still have two different sizes of pixels. This would be even more confusing in a vector application than the fixed conversion rate. Essentially you would have one more problem.

  • Disallow pixel and physical units from mixing

    This still wouldn't solve your problem. This is essentially the right solution but would require 80% of users to redo basic math courses so not realistically an option.

Ok, whats going on? A vector drawing application is a page description language. As such it can have many separate sizes of pixels in the same document. It is perfectly possible to have two images of the same physical size on the same page. So imagine you import two images one at 150 PPI and one at 300 PPI (yes your using DPI technically you sgould say PPI). So now what?

Well since adobe decided to use the first option they have just defined one pixel as 1/72 th of an inch. So your image is correct

72/150 * 6016 = 2887.68

Which is what you see.

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  • Thank you for the detailed response! For some reason, I am still having a hard time wrapping my head around this, but I'm getting there. The math makes sense, I get the conversion taking place. But, It still confuses me why a 3000x3000px document at 150ppi is showing a roughly 6000x6000px image at 150ppi as smaller. Shouldn't it appear twice as large as the artboard? Why does illustrator use 72ppi as a conversion factor for representing my image when I set the document to 150ppi? I want my image larger, but it's already at "100%" scale. Does that matter?
    – Emily Werner
    Jan 31, 2020 at 16:46
  • @EmilyWerner artboard describes a paper a raster image may have any size on paper. Paper offcourse has no pixels. Turn your units to say centimeters makes much more sense. Pixel as a unit is not the same thing as a pixel as a element on a image, because there could be many images with different sizes of pixels. And a unit can only ever have one value.
    – joojaa
    Jan 31, 2020 at 16:54

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