Let me be the first to say that I know nothing about newsprint, printing or ink, and lack the wisdom and experience our friends at prepress or Adam Drew may have about how those things impact the quality of printed design. This made it extremely difficult to know when to use inverse text and why forgoing it may be a better option.
Instead of printing an entire story half on a photo and half on rich black (see spring 2013 – yikes!), take a cue from this explanation shared by the Scripps central desk design director himself:
The above may look fine on the screen, but was very hard to read on the newsprint. This cutline was inversed on a color made out of three inks: C, M and Y. None of them are 100%. That’s actually the main problem.
Colors at less than 100% or halftones are made out of tiny dots of ink. These dots patterns are smaller as we use a smaller color percentage. These are also called screens. Like this closeup of a white letter on a screened Cyan or Cyan halftone:
As you can see, because the color is made out of tiny dots, the shape of the letter is NOT perfectly defined.
Only the color in 100% will bring a perfectly defined shape for inverse type
So when we use inverse type on a color made out of two screened ink colors, like this:
The letters’ shapes are not perfectly defined. They may read well only if the press has an accurate registration. Which is difficult for newspaper presses.
If the press doesn’t have accurate registration, the definition on the letters will be even worse. Like this example below made out of a screen of Cyan and a screen of Magenta with poor press registration:
So, anytime we use an inverse type on color shades, it will be a lot better to use one of the inks in 100% or very close to that. And this will have to be either Magenta or Cyan. Yellow is too weak to do this.
Using one of the two tones (Cyan or Magenta) at 100% or closer, it will define the letters’ shapes clearly, and if there’s a failure in press registration, the definition is much better than using percentages.
Like this example:
The second example is this:
If we are using inverse type on top of photos or shades. If the background is too light, then try black type. If it’s in the middle, (not light, not dark) than it’s time to look for another resource.
I’ve also provided a link to a PDF created by one of the lead designers about Contrast & Type
. This further explains inverse text and how contrast and font size and type play in to whether text is readable.