LCD projection and HD

[Matthew OSullivan]

Hi, newbie here to HD and to these forums... sorry if this topic has been covered elsewhere but I can't find it in a search. I posted this in the HD forum as well.

 

A fast upcoming HD shoot features rear-projected video. The playback will probably be NTSC DVD video, coming from a laptop and projected with an LCD (not DLP) projector.

 

Should this be smooth as butter, or are there any potential flicker/judder issues?

 

Thanks for any hands-on feedback!

 

Matt

[David Mullen ASC]

Should be OK.

[Matthew OSullivan]

Fastest reply in history. Thanks David! Have you done a similar thing with success? And, the original source is 24fps film, transferred to video. Might this cause any problems (aside from possible judder on slow pans)?

[David Mullen ASC]

Haven't done it myself. Lester Dunton, who set up a big projection system for "Derailed", told me that he felt that for film projects, it worked better when the plates were also shot on film. Although personally I would think since the view out the windows is supposed to be "reality", some sort of high frame rate, grainless digital image would work better and let the movie camera capturing the scene add the film look. Maybe he was thinking more in terms of film's superior exposure range working better for background plates.

 

Anyway, I believe even when showing 24P material, the LCD projector is using a higher refresh rate than 24Hz, so you might only have some motion strobing problems now & then for fast motion on the plates interacting with fast motion on the camera. But generally with projection, one or the other has a lot of motion, usually not both.

[Matthew OSullivan]

Interesting... thanks again. We might be going that way (out the window "reality") a lot in future, as we've done in the past with still images. I agree that the cleaner the projection the better... good thought about the dynamic range - he might also be thinking about matching stock?

 

The thing at hand is an artsy montage of "memories" to be projected behind the actors, and there's no need to simulate reality - it can even look kind of dirty or have some low-fi look. At the moment I'm just concerned with any flicker issues due to the various factors of projector Hz, LCD decay rates, frame rates, etc. But you think this should be fine showing NTSC projection to HD camera? I see no reason why not. The projector should be around 60Hz minimum.

[David Mullen ASC]

NTSC is rather low-rez so hopefully your backgrounds will be out of focus anyway.

[Michael Nash]

I was gaffer on

, Mike Rizzi was the DP.

 

Shot with an HVX200 at 24PN. The LCD rear projection was fed by both DVD playback and live feeds from DVX100's. I believe the DVX's were set to 24P, although I can't say for sure now. In any case, there were absolutely no problems with flicker, and live monitoring on an NTSC monitor also looked fine.

 

The only potential problem I see with 24fps film>60i video>60i DVD playback is you could potentially see some "combing" on some of the field-split frames containing horizontal motion. 24fps film>24P video>24P DVD playback would avoid this, or shoot 30 fps film>60i video>60i DVD. I would think the faster motion sampling of 30fps might be better to create "reality" for the BG element anyway.

 

I remember reading that the show 24 used to use a Sony PD150 (interlaced NTSC) to shoot background elements for LCD rear-projection in their helicopter scenes. I guess the BG's must have been out-of-focus enough to hide any possible combing or aliasing in the NTSC material.