I've got a Lumagen HDP and have been checking out the difference between inputing a progressive signal and an interlaced one via HDMI, I've got a Pioneer 989 DVD player. I've found the progressive signal to be a bit sharper than the interlaced one, this is using a still image from DVE, so no fields to sort out. I tried the force film mode on the HDP and it didn't make any difference. I would have thought they should look the same.

I thought it might be the player doing something different to each signal, so I tried it with my GameCube. Booting up a game in progressive and interlaced, looking at a still menu frame, same result. I also tried going direct into my projector (Epson TW700) and forced the different deinterlacing settings there, same result.

Is it just something in the process of generating an interlaced signal that you'll lose abit of information, and therefore sharpness when weaving the fields back together?

If so, it means that inputing an interlaced signal into your processor to make use of its deinterlacing capabilities will cost you abit of sharpness.

Maybe this is a good case to use DVDO's deinterlacing of progressive signals (is that out yet?)

In the case of your game cube, it is typically using 2:2 cadence, and so you don't really lose much in the interlacing/deinterlacing process. Still, in many situations, there has to be some loss of sharpness inherent to the deinterlacing (or even interlacing) process.

I would first set your HDP to show you if you're in Video or Film mode (There's a remote control menu sequence that does that).

if your source is inherently progressive, it's always better to output that. The problem is when you have a DVD or another source that's inherently interlaced. That's where you want the processor to deinterlace it.