Let's say we have a reel that has very consistant densities save for one small section, perhaps an eight page issue, that was spliced into the reel. This scenario actually happens a lot with older film. Let's say, now, that this spliced-in section is clearly over-exposed as compared to the rest of the reel. Taking a reading from this section will significantly alter the reel's average density, especially if the technician takes only 6 readings from the reel. Do you under-expose the reel to accomodate for the over-exposed section, or is it better to expose for the reel and sacrifice the small section? A good duplicating technician can find a happy-medium to produce a more consistant and acceptable reel of microfilm that can be digitized with good results.