A microfilmer's job is to capture everything you give them. If they're filming a bound volume...

• they capture the bound volume covers (a rarity with older microfilm)
• pages are filmed exactly as they are bound even if they're out of order
• bound volumes tend to interleaf supplements inside an issue. Modern standards would have supplements filmed (bound) after (behind) the proper issue

In a perfect world, pages are unbound and filmed individually. Loose pages filmed under older microfilm standards are often stacked one atop the other...

• this can affect the resolution i.e. decreasing focus
• if there are excisions, such as obituaries, you won't necessarily notice unless you read the paper or assign bounding boxes and/or article classifications

Ideally the microfilmer will place a black sheet of paper behind said cutout (again, this rarely happened in older film)

The best possible orientation for a newspaper is 1A. Older papers were often filmed in a 2B orientation to save space, even if it meant filming at a reduction so high that the paper barely fit inside the exposure...

• this filming method is especially problematic for the NDNP spec that demands no less than 300dpi

Microfilmers are easily distracted. The usual result is duplicate, sometimes triplicate, page images...

• to be fair, not all duplicate images come from the microfilmers. Darkroom technicians have been known to splice in a refilm without first removing the section that needed refilming!

Pre-standards film didn't care what a microfilmer used to hold down corners or flatten pages (arms, pencils, ashtrays; you name it, they used it)

Microfilm cameras have a device called a "gate". The gate increases or reduces the size of the camera bed being exposed. Preferably, the gate is closed such that there is a 1" margin around the page. Older film didn't always care about the gate. Many times you'll see cords, shirts, adjoining tables, and even the camera head tower in the exposure.