you might want to take a look at the inexpensive computer microscopes. You can buy for less that $80 and have a large picture on your computer screen that is from 10X up to 60x or so. (You can buy much higher magnifications with a much higher price) I bought one on eBay for $60 and it is well made with good quality work. I use it to check gemstones for flaws and faceted faces for potential re-cutting and/or re-polishing. Most come with software and very easy to setup and use. A standard jeweler's loupe does not show enough area to be useful. You can also take a look at map makers magnifiers that are on legs the right height to focus on a map (or other printed matter). Hank

Exactly what are you scanning?

Digital images that were printed? Those would possibly have pixelization (and possibly "noise"), but not grain.

Traditional photographic prints? Those may show some grain (depending upon the ISO/ASA of the original negative or slide), but won't show any pixelization.

Black & white prints typically exhibit more grain than color prints. But it really depends a lot upon the original film type and the printing method used.

If you are scanning half-tones such as images in books, magazines and newspapers, those will exhibit dot patterns that make up those images. Magazines and books are commonly 120 to 180 dpi or higher. Newspapers are commonly under 120 dpi. Monochrome images will show the dot pattern more obviously than full process (4-color) printing where there's often some perceptual blending of the multiple inks.

Whenever you scan there is some "gain" with grain, noise or pixelization... Each new generation of an image tends to add a little (or a lot if done carelessly). They can be kept to a minimum with careful post-processing and some scanning software can automatically reduce them (ICE, Silverfast AI, etc.), but you may see some loss of fine detail if those are applied too heavily. More sophisticated NR software might be helpful too. (I use Lightroom's, Photoshop's, as well as Photoshop plug-ins Nik Dfine and Imagenomic Noiseware. The last is the most sophisticated and versatile.)

Like some others, I really don't see any purpose to a loupe. It is what it is. What really matters is the unmagnified appearance of any digital file displayed online or any print that's made from the original. Size reductions would minimize the appearance, while any enlargement will tend to amplify it.

Note: Viewing digital files "at 100% in Photoshop" is actually pretty silly. A file from a 24MP camera that's displayed on a typical monitor is like making a 40x60" print, then viewing it from 18 or 20" away... far larger and far closer than most "real world" uses. If making an 8x10 or 11x14 print from that file, it would make a lot more sense to evaluate image pixelization, sharpness, graininess, noise and even focus "at 25% or 33%". Sure, it's fine to zoom in to high magnification while doing fine retouching and corrections to images.... But it's unrealistic for a lot of the evaluations. Depending upon the resolution you scan at, you might bee seeing similarly ridiculously over-magnified images "at 100%" on your monitor... far beyond what you'll actually be using.