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There's no way this flatbed scanner will actually realize 4800dpi. Epson's 4800-6400dpi models max out at 2100-2400dpi of somewhat softish resolution. The Canon won't be much better; likely a little less. The old but quite popular Canoscan 9000F managed about 1700dpi (from a nominal 4800). I see no reason to expect the modern variant will perform any better.
Fortunately, your solargraphs are likely on formats much larger than a 35mm film frame, which means that even a scan resolution of, say, 1200dpi will likely be more than you'll ever need.
Keep in mind that most of the discussion on this forum w.r.t. flatbed scanners will revolve around their use as film/transparency scanners. The Canon LiDE400 AFAIK is a document/reflective scanner exclusively. This is perfectly fine for your solargraphs on paper, of course.