I just want confirmation on what I am thinking is true.
So I print product boxes, and normally photography comes into me at 180-300dpi.
A recent photo shoot came in at 72dpi, but still the same file size as most photos, so the image was more than large enough to print.
I put it in illustrator, and scaled it down about 25%. The printed version came out blurry while other photos on the box were fine.
If I change the image in Photoshop to 300dpi and put it in illustrator, I don't need to scale it down at all as it has brought the pixel size down.
My question is: When I scaled the 72dpi image, did it print the scaled size at 72dpi hence coming out blurry? I thought it would print the same because it was compressing the image to be more detailed and the dpi at that point wouldnt matter?
I am just guessing that illustrator just prints that image at 72dpi after being embedded no matter where I scale it too, and that it should always be >180dpi even if the file size of the image is the same?
Yep. It prints blurry because it has to scale the image - Illustrator SUCKS at resizing and doesn't do it right at all. You should always scale to the correct size in Photoshop and then open in Illustrator. The main reason is that Illustrator only references the original file, depositing it into the final print as postscript raster data when you go to print - the scale is referenced from the original file and Postscript also sucks at resizing (worse than AI).
Incidentally, if you are just doing basic cut lines, try doing them in InDesign (ID) instead - InDesign is a sort of go between PS and AI. You do it the same way - load your path from AI in ID, then load your scaled PS file. Lay your outline over the top of the PS file and then make your mask and go from there. I like ID because you can tell it to edit either PS or AI files directly in PS or AI, respectively. It's a layout app, like Quark Xpress, but I find it easier to use than Quark Xpress.