One serious option for very high resolutions is to use a good tool for increasing resolution. These programs work well for doubling resolution.
Looking at examples for photo zoom pro 4, for example, the results are pretty good (bear in mind the purpose isn't to sharpen the image but to provide meaningless detail for pixel peepers — from a sensible viewpoint, the image looks the same).
Ken Rockwell (the opinioned photographer) suggests saving all photos as max quality JPEG at a fixed resolution and if a client asks for a higher resolution tiff or whatever you simply convert it using photoshop, because no-one can really tell the difference. I believe in keeping as much data as you have, but I think he's pretty much correct.
Looking at examples for photo zoom pro 4, for example, the results are pretty good (bear in mind the purpose isn't to sharpen the image but to provide meaningless detail for pixel peepers — from a sensible viewpoint, the image looks the same).
Ken Rockwell (the opinioned photographer) suggests saving all photos as max quality JPEG at a fixed resolution and if a client asks for a higher resolution tiff or whatever you simply convert it using photoshop, because no-one can really tell the difference. I believe in keeping as much data as you have, but I think he's pretty much correct.