I recently scanned 3 4x5 transparencies. The original scanned files were 23,000x18,000 pixels. For my website, they were shrunk to 4,000x3,200. I think that's a reasonable size. The photos were captured near San José, California, in Alviso, California. My vintage scanner is still chugging away. It's an Epson Perfection 4870 Photo.
