Background color for photo: "paper" or "none?" Does it matter anymore...?

It’s worth noting that the Overprint Preview (the print soft proof), and the Transparency Blend space settings can have a significant affect on the appearance of a [Paper] filled object when it is interacting with transparency—for print projects you really have to pay attention to the Overprint/Separation Preview setting.

Here the Transparency Blend Space set to CMYK with Overprint Preview turned on and off:

Same page with the Transparency Blend space set to RGB:

The same will happen in Photoshop when the Background layer is filled with 100% transparent pixels vs. 100% opaque white pixels.

Overprint Preview also works differently with process vs. spot colors:

https://community.adobe.com/t5/indesign/indesign-rendering-illustrator-linked-graphics-differently-across-pages/td-p/10873261

Yes I remember doing this too. It was to compensate for a Quark bug that would make some graphics that had contours come out "jaggy" so the frame always had to have a paper color.

In InDesign the frame can be whatever color is required.

When it's set to paper - and you make a PDF - you can turn on the transparency grid in Acrobat Preferences.

Under Acrobat Preferences

Page Content And Information

• Show Transparency Grid: Displays the grid behind transparent objects.

I get it...that paper is the actual paper color (I'm not trying to duplicate the look of it) I'm not trying to set it here. I'm assuming that the paper is "white" or "cream" or whatever, and that will happen when it's printed.

The question is: is the quality of the image, when reproduced...or the processing time for the printer (commericial 4-press printer) the same if I have a book filled with images that are (not needing a transparcncy setting) and either loaded into "container boxes" of "paper" or "none?" If there are quality or processing time issues, that's all I'm concerned about. It's a pretty basic question. Nothing fancy, no transparency, no k.o.s, and no "layers." I will keep them "none" unless I should change them for a reason.

And thank you for your response!

You should be using [None].

In simplest of explanations, the [Paper] colour in InDesign is really to allow you to change what your background is in your document to simulate the paper you are printing on. Most times, of course, your paper is white (or near white) so it's not really something people change often. But, say, you are printing on a coloured paper (like a cream stock or a kraft envelope) and you want to see on screen what your design will look like on that stock, you can edit [Paper] to something that approximates that colour. This is purely for the screen, and does NOT show up in output files. If you colour an object with the modified swatch, it will output with as if it was white.

Therefore, you giving your images a background of [Paper] is like laying a sheet of paper between your image and whatever background items you have. This will affect how certain Transparency effects work when applied to the image itself within the frame, e.g. Multiply.

The default [Paper] swatch is unique and represents the actual paper color with no ink printed. If I set the [Paper] swatch to pink, a blank page will display as pink—doesn’t matter what the [Paper] swatch color mode, or Overprint Preview setting is:

If I make a CMYK 0|0|0|0 White swatch and use it as the fill for the container frame holding a transparent PSD it will preview differently depending on whether Overprint Preview is turned on, but the output values for [Paper] and 0|0|0|0 White will be the same:

Overprint/Separation Preview turned Off

Overprint/Separation Preview On: