My new Epson 4490 is allowing me to do comparisons between different lenses, films and aperatures. The following is a test of my Vivitar 135mm f/3.5 T-mount lens. The scans are at 3200dpi. Given some testing I have found that 3200dpi reveals a bit more detail then 2400dpi, but not a huge amount. 3200dpi really is the very edge of what the scanner can competently handle. The scans are deffinitely enough for an 8×12″, but really not any better without some up-resing utility.
The crops were taken from middle right (right most deck latice work). 100% enlargements at 3200dpi
As you can see at f/3.5 the lens is pretty soft, but at f/5.6 is sharpens up a fair amount and f/8 is just a bit sharper. At f/3.5 the lens is capable of acceptable 5×7, at f/5.6 and above an 8×12 would be acceptable (especially at f/8-f/16). The lens is not super sharp, but for a 3rd party lens that is more then 40 years old it isn’t to bad if you don’t mind stopping down a bit.