It's possible to watch the Effective PPI of raster images when you are scaling them within Illustrator by using the Document Info Panel ( Window > Document Info then choose "Linked/Embedded Images" from the panel menu, whichever is appropriate) It's best to place the image at the desired output size and resolution, then reduce and never enlarge the image beyond it's original dimensions. So, if the image is enlarged too much the overall image quality may suffer due to less PPI upon output. If you place a 300PPI image into Illustrator, you can reduce/enlarge it as you please, but you won't change the image pixel data. An image enlarged by 200% will effectively half the PPI. Again, the effective PPI of the image is changed not the actual pixel data. (square root of total pixels, divided by dimension, equals effective pixels per inch)Ĭonversely if the image is enlarged, to say 12"x12", in Illustrator the total number of pixels are stretched to fill the enlarged dimensions, but the PPI remains the same. In order to figure the effective PPI for a raster image one works backwards. An image reduced by 50% will effectively double the image PPI.
In other words, Illustrator "condenses" the total number pixels into the new dimensions, meaning the change effectively alters the image PPI. With Illustrator, if this image is reduced, to say 3"x3", the total number of pixels does not change. the original image size 100%) the PPI will still be 300PPI upon output.Įxample (using simple dimensions for clarity):Ī 6" x 6" image 300ppi has a total pixel count of 3,240,000 pixels (3.24 megapixels).Ħ" * 300PPI = 1,800 (pixel dimension).
If the image is then output "at size" (圆, i.e. Quick Answer: It is possible to place something like a 300PPI image into an Illustrator document, reduce the image within Illustrator to 1/6th scale. The pixel data in a raster image remains the same, regardless of what one does in terms of scaling the image within Illustrator. Unlike raster image editors, Illustrator does not interpolate raster data.
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