Pixel dimension for same physical size is wildly different in Photohop and Illustrator

[stephanie28346195yge9]

I have Photoshop CS5 and Ilustrator CS6.

I wanted to make a template in Illustrator of a specific size, 210mm x 100mm.

When I made a new file with an artboard of 210mm x 100mm, the pixel dimension was 595.28px * 283.46px which is way off the expected 2480 x 1181 pixels. The expected dimensions comes from this calculation:

Converting mm to inches then multiplying the inches by 300 which is the DPI (resolution).

So then I made a template in Photoshop with the same physical size, and the pixel dimensions (after mm to inch and inch to pixel conversion) was indeed 2480 x 1181 pixels.

What is happening and how can I output a file of an accurate dimensions in Illustrator?

[stephanie28346195yge9]

Question Poster here.

I did some more tests and discovered that the file I created in Illustrator with pixel dimensions of 2480 x 1181, when exported from Illustrator as a jpg and opened in Photoshop, has a massive dimensions of 874 x 416mm instead of the intended 210mm x 100.

When I made a rectangle in Photoshop with physical dimensions of 210mm x 100mm and exported it as a jpg, then opened it in Ilustrator, the physical dimensions remained the same, but the pixel size (you can check the artboard size in other units such as pixels by going to File -> Document set up -> click on "Units" in top left corner and select a new unit -> click "Edit artboard".) was 595 x 283px so there is something going on with the pixel size in Illustrator.

[c.pfaffenbichler]

Image Resoltion is given in ppi, not dpi!

Illustrator is a vector oriented application. 

It probably just assumes 72ppi (what with tradition). 

But your description seems a bit unclear to me, please post screenshots with all pertinent Panels visible. 

[stephanie28346195yge9]

Yes I know digital resolution is in PPI and not DPI, but since I am using Photoshop for ultimately a printed product (to a required 300 DPI), I chose to use DPI fo convenience in my mind, apparently to your displeasure. We can quibble over D or P but the issue remains, the conversion size is different between Photoshop and Illustrator.

[c.pfaffenbichler]

Yes I know digital resolution is in PPI and not DPI, but since I am using Photoshop for ultimately a printed product (to a required 300 DPI), I chose to use DPI fo convenience in my mind, apparently to your displeasure. We can quibble over D or P but the issue remains, the conversion size is different between Photoshop and Illustrator.

Well, it seems the requirements you were given used the incorrect unit because a digital image does not have »dpi«. 

What are the pixel dimensions of the psd you exported with 300ppi Resolution? 

Can you please provide the ai and the psd? 

[stephanie28346195yge9]

I can't attach the actual thing I am working on, so here is a template instead, that was made in Illustrator CS6 and 210mm by 100mm. This item can then be exported as a JPG and the export opened in Photoshop (ie, I do not have a Photoshop file). When opened in Photoshop, the pixel dimensions are different in to what it was in Illustrator.

Also I just realised the intrinsic pixel dimensions of the exported JPG itself is different to what Illustrator displayed it as when the properties are viewed, even without opening in Photoshop, as seen in the screenshot.

For comparison, here is also a file I made in Photoshop CS5, to 210mm by 100mm in Photoshop. When exported as a JPG and opened in Illustrator, the pixel dimensions changes.

I need a template to a physical dimensions specs in mm (which is easier to do in Illustrator) but then upload it to a printing platform where it has to be of a certain number of pixels wide and high as well as a minimum D, not P, PI (the platform said 300 DPI which yes, I do know is dots and not pixels per inch), whch is why I then open it in Photoshop to check the size and resolution and add other edits as needed.

[c.pfaffenbichler]

Then I think you should stick with the intended dimensions in mm in Illustrator and export at 300ppi – if the print provider explicitly requires pixel images and does not accept pdfs. 

[D Fosse]

Yes, it's been a long standing gotcha that Illustrator just assumes 72 ppi in many situations. Not sure if that's still happening, but it certainly did in CS6. I haven't re-tested it now, but I remember many such cases from the forums.

The disconnect happens because Illustrator, as a vector application, defines data as physical dimensions. It doesn't do pixels, except as a secondary recalculated unit. Photoshop, on the other hand, works only with pixels, and physical size is a secondary recalculated unit.

What ties these two together, and allows translation from one into the other, is the ppi number. That's the translator. It has to be consistent, and if it isn't, you get this.

[c.pfaffenbichler]

And as an added bonus Illustrator can declare an object/artboart to be 595,2756 px by 283,4646 px whereas a Photoshop image’s dimensions cannot contain fractional pixels.  

[stephanie28346195yge9]

Can you tell me where to see this "72 PPI" in Illustrator setting? I never knew Illustrator uses 72 PPI. When I create a new file in Illustrator, I get the option to choose and by default, at least on my computer, it is 300, as seen in the screenshot attached here.

[stephanie28346195yge9]

Another screenshot of the panels in Illustrator showing the settings when I export.