Thank you, Charles Badland:

Is my understanding correct that Illustrator and Photoshop convert pixel width and height to inches differently? And, are you recommending that I specify my width and height in Photoshop in inches, not pixels?

I always work in either inches or picas (certainly both are "real-world scales" as you note) in Illustrator (Edit > Preferences > Units & Display Performance > General Inches).

I referenced pixels because Photoshop is a pixel-based program.

In Photoshop I work in inches or in pixels, depending on what Im creating.

I trust Illustrator and Photoshop to give me conversions of pixels to inches and vice versa, but I had no idea that they would be different, and I do not understand why at this time. What explains this?

While I understand pixels are units of measure for screen display, the image itself must have a true size (and resolution), which when enlarged and printed (beyond the true size) becomes pixilated. (I know this is correct. For example, right click and save any image from the Web, then enlarge it beyond its true size, and the printed copy will be pixilated.)

Working in Illustrator: When I enter pixel width and pixel height in the Rectangle Options, the measurements automatically convert to inches. Thus, entering 300 px (width) and 300 px (height) yields a square of 4.1667 x 4.1667 inches, as Illustrator automatically converts the pixel dimensions to inches. Also, this is shown in the Transform palette.

Is this a correct size, or simply arbitrary?

Photoshop also creates a size in inches based on the pixel width and pixel height specified, but it is different. For example, entering 300 px for both width and height yields a 1 x 1 inch image (Image > Image Size).

When I created my Photoshop document, I entered the pixel width and height I needed, not inches.

Following your explanation, I experimented by creating two documents in Photoshop: (1) Specifying width and height in inches (rather than pixels); and (2) Specifying width and height in pixels (rather than inches). When I placed the *.PSD files into Illustrator (Edit > Place) on the same page, side by side, sure enough, their sizes are different. Wow! Since both are coming from the same program, why are the different? And, which size is correct?

Of course, when saving the documents in Photoshop, the one created in inches yields a much larger file size (which may create problems of its own that I will have to handle next).

Thank you again for your answers, and please let me know if my understanding is wrong.

Does anyone know why Photoshop and Illustrator would convert pixel dimensions to inches differently? And, is there any way to program Photoshop to convert pixels to inches in the same way as Illustrator to eliminate mismatched image sizes?

wcwarren

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