I obtained an image from DPL in 2008 and it came on a CD with a resolution of 600 dpi. This was of a copy scan of an image from a photo album -- the view of the special train at Mound House, Nevada, about ready to leave for a day long trip to Keeler. I can go in quite nicely and see detail. For my use it worked out very nice -- used on the last (outside) page of an issue of
Journal of the Southern Pacific Narrow Gauge Historical Society at close to the original 8x10 print size
The other year I talked with Joe Strapac who has published the series of SP diesel soft-cover books. He says that for image reproduction he desires an image that would be 600 dpi from an 8x10 print -- or the equivalent (i.e. a 1200 dpi from a 4x5 print).
Brian Norden