Digital Light & Color

It seems that the framing makes a halftoned image kind of antialiased.
It is not necessarily, it may even improve the result by making the image more contrasty, but it is of the user's control.

The Frame transformation generally resamples the input image. To avoid this, set Base Size On to Fixed Image Width and then set Target Width times Resolution equal to the input image width in pixels.

While I was trying, just out of curiosity, to do away completely with the visible difference and avoid resampling, I found that the Target With would have to allow five decimal places because, in my example, 6,3325 inches were too much and 6,3324 were not enough.

But as I said, resampling can and in fact will improve the image quality by suppressing too bright white dots in dark areas. I would dare to say that it is a more welcome than unwelcome effect.

To simulate the effect made by Frame without using Frame I used Resize, set the output size just one pixel smaller and got the same result. It is a simple but interesting step and perhaps might be added straight to Halftone transformation in the form of an option check box.