Why a bigger picture than page is enlarged rather than shrinked in InDesign?

Question

We want to prepare a book for electronic publishing on iPad by using InDesign. Hence in the InDesign's Document Setup we entered as intent 'Digital Publishing' and as page size 2048px X 1536px.

We took a photo output from a Canon 5D Mk III and processed in Photoshop CC and imported it (by Place) in InDesign eiter via TIFF or PSD.

The image(s) is/are 5380px X 3704px (a very small crop was done). The dimensions are according with Photoshop CC's info and XnView MP Properties pane - I mention just two programs which say the same. Also knowing Canon's 5D3 sensor's resolution, the numbers are quite logical.

However, in InDesign CS6, the photo appears as a 1614px x 1111,2px image and in order to fit it to the width of the 2048px page, we must enlarge it at 126,88%

Why is that? Why a 5380px X 3704px photo is placed in InDesign as an 1614px x 1111,2px image? (approx. three times smaller)

Perhaps I should note that the recorded DPI in Photoshop's file is 240x240 but I assume that since I set up the InDesign document to be for 'Digital Publishing' and the units are pixels, my image should remain at the same pixel dimensions.

Answer 1

Here's what's happening under the hood: regardless of the fact that you have a pixel-based document, InDesign can only work with it as if it were a paper document.

InDesign "thinks" in physical dimensions. As far as it's concerned, 1 pixel == 1 point. Since there are 72 points to an inch, InDesign considers there are 72 pixels to an inch. As far as the program is concerned, that 2048 px page size is "really" a 28.4 inch page size.

When you place a 5380px, 240 ppi image, InDesign sees that as 22.4 inches (5380/240) and places it at that size on the 28.4 inch (2048 points) page, not as pixels relative to your pixel page. Even though your ruler bars and document setup say "pixels," for layout purposes InDesign sees points.

Despite gaining the capability of working in pixel dimensions and RGB, InDesign is still a print application at heart. It constantly thinks in physical, printed sizes. The engineering involved is deep in its DNA and undoubtedly very hard or even impossible to change without creating mayhem elsewhere in the program.

If you select your image and press F8, the info panel will show you "Actual ppi" (240) and "Effective ppi" (800), since InDesign hasn't changed the original image size, just the size "on paper."

InDesign (like all Adobe apps) considers 72pt == 72px == 1 inch, a fact that has other consequences you should be aware of. If you export your page to a raster format such as jpeg, it will be 2048x1536 only if you export at 72ppi. Export at 144 ppi and you won't get a 2048x1536 image with 144 ppi in the metadata, you'll get a 4096x3072 image with 144 ppi in the metadata.