always a 3rd party rom will give you more control than stock.
what options do you have on your camera in terms of storage? MASS storage? LUN?
what adapter are you using?
I have a sony a99 and ill connect it up to the phone and report back...
I see the dev has an amazing support forum. have you contacted the dev about his app and if the htc is compatible?
<<-- post your question there and get direct suport as the op on this ticket has the same issue