Seems that WIA drivers shows up using TWAIN_32.DLL (Twain 1.x) while they don’t with TWAINDSM.DLL.
Why ? Searching for WIA in specifications gives nothing.
Are you talking about WIA 1.0 or 2.0?
32 bit or 64 bit?
32 bit, to my knowledge there is no 64 bit WIA drivers for professional document scanners.
Any WIA driver visible with TWAIN_32.DLL
TWAIN_32.DLL can only use 32 bit TWAIN Drivers. And the 32 bit WIATWAIN layer can only use 32 bit WIA Drivers.
But 64 bit WIA exists.
For your reference, we have developed professional 64 bit WIA Drivers for document scanners. So it is possible.
I wondered why TWAINDSM.DLL (32 bit) does not show WIA drivers while TWAIN_32 does.