PPI vs DPI export - Resolution resampling clarification

[wckdtall]

Knowing Illustrator operates at 72ppi, I'm looking for clarification on how the resampling works when exporting higher resolution.

If I have a 300ppi image inside a 72ppi document and export at 300dpi, is it resampling the image @ ~416%? Or is it 300dpi at the physical dimension of the artboard in inches?

Mainly asking, as the pixel dimensions are 1000 pixels(AI and Bridge) @ 72dpi, vs exporting @ 300dpi it's 4167 pixels.

The links panel looks like the dimensions match the 300dpi export, but just curious as the measurements are a bit confusing.

Looks to me like the image is 300dpi based on the physical size of the document and not the pixel dimensions.

[Anshul_Saini]

Hi @wckdtall,

Great question! Illustrator uses PPI (pixels per inch) rather than DPI for export settings. Let’s clarify how this impacts resolution and resampling during export.

Illustrator’s Export Process and PPI

1. Illustrator artboards work at 72 PPI by default, meaning that if you create an image with, say, 1000 x 1000 pixels at 72 PPI, that image represents a physical size of about 13.89 x 13.89 inches on the artboard.

2. When you export a document at a higher PPI (e.g., 300 PPI), Illustrator resamples the entire document to match that specified resolution.
Here’s what happens:

• If you set the export PPI to 300, Illustrator scales the document accordingly. So, a 1000-pixel image created at 72 PPI will export at approximately 4167 pixels when set to 300 PPI.

• This does not resample the original image within the document itself but scales the output to produce a higher resolution image based on the specified PPI for export.

Hope this clarifies it better! Let me know if anything else needs explaining.

Best,

Anshul Saini

[wckdtall]

Thanks!

Is it correct to assume, that all vector based portions of the graphic are scaled higher for output, and the raster items are scaled up or down only if the output resolution doesn't match?

Below is a test with an image at 1000pixels within the document, vs the pixel dimensions of the document itself.

Generally I think in the terms that if I have a 900dpi image, I can scale my graphic to 3x the size and it will be 300dpi. Looking at the relationship of physical size here is a bit confusing, as in photoshop dpi is relative to the physical pixels of the document itself, although I guess this would be similar to links or smart objects.

[Brad @ Roaring Mouse]

"Knowing Illustrator operates at 72ppi"

Not really, no.

Yes, dimension-wise, there are 72 points in an inch, as is anything typographical would be, but that doesn't define the resolution. Vector objects sent to a printer, of course, are rendered at the resolution of the ouput device, and any high-res images would carry through. Illustrator does NOT reduce them to 72ppi in any way. However, if you are exporting to an image-based format, Illustrator will export at the resolution you select. Points and pixels are associated on a one-to-one factor. Hence, say you have designed a document that is 500 pixels wide x 200 pixels high, Illustrator sees that as 500 points wide x 200 points high, so to export an image at exactly 500 x 200, you would select the Screen Resolution (72ppi) setting in Export. Exporting with higher settings would create a much larger image according, Medium at 150ppi (1042 x 417) and High at 300ppi (2084 x 834).