Question about 24P and Computer Monitors...

[moontrip]

Hi, everyone. I'm curious about something that I can't find the answer to in all the reading I'm doing. Here's the basic question:

Is it ever possible to watch 24P DV loaded into your computer played back in true 24P on your computer monitor?

The reason I ask is that as far as I can tell, most computer monitors in the U.S. (if not all) are 60 field progressive scan monitors. So if you're editing on 24P video in Final Cut Pro, on a 24 frame timeline, and you've removed the pull-down frames, are you actually seeing 24P played back on the computer screen? Or does the computer add the pulldown back and simulate the 24P as you watch it?

On the same topic, are there any external monitors out there that can actually play back 24P, or are all U.S. monitors (including HD) based on the 30/60 standard?

Thanks in advance for your help. I'm totally confused on this subject.

Bill

[redwudz]

I don't think you would have a problem with the computer monitors. This site has some information about the format: http://www.adamwilt.com/24p/#24pRecording

[moontrip]

Thanks redwudz. I've actually read that page before, and unfortunately it doesn't really get very technical as far as playback on a computer monitor is concerned. I know you can play back 24p footage on your computer monitor and on an NTSC monitor. But my question is whether or not you can actually get true 24p playback, or if you're always watching a realtime conversion of the 24 frames into 60i or 60p. Thanks...

Bill

[BJ_M]

it is a conversion -- but there are monitors and projectors which are modified (used in the film industry) to play back 'true' 24p ...

[junkmalle]

Is it ever possible to watch 24P DV loaded into your computer played back in true 24P on your computer monitor?

I don't think there are any monitors that can scan that slowly. You wouldn't want to watch at true 24p anyway -- it would flicker like crazy. Note that even film movies in theaters are show at 48p -- each frame is displayed twice.

Assuming your system is set up to switch frames during vertical blanking, what happen is the frames are repeated to get as close as possible with the refresh rate of the monitor. For example, if you set the monitor to 72 Hz refresh you will see each frame 3 times. At 60 Hz some frames will repeat 2 times, some 3.

If your system doesn't wait until vertical blanking to switch frames you will see a torn image where the top part is from one frame and the bottom is another.

[moontrip]

Okay, thanks, junkmalle and BJ_M, for your responses. What you're saying makes sense...but it also raises new questions.

I'm not sure if this is the right forum for this topic, but now I'm confused as to why shooting DV in 24p (with a prosumer camera like a Panasonic DVX 1000a) gives you more of a "film" look than 30i. If the whole process from both a shooting perspective and a playback perspective is really a cheat, with pulldown frames being dropped and added, then isn't it all semantics? If you're staying in the video world (and not actually outputting to film), why does 24p deliver a different image on tape than 30i? I can understand how changing the gamma settings can give you a different recorded image, but why should the frame rate, especially when it's a cheat, make your video look different?

Also, junkmalle, can you actually change the refresh and vertical blanking settings on your computer system? I'm working in the Mac world, and I didn't know that was even possible...

Thanks for your help on this subject, I really appreciate it.

P.S. Are films really projected at 48 frames per second?!?! I can't believe I didn't know that...

[junkmalle]

I suspect 24p lets you use longer exposures resulting in more motion blur. With 30i each exposure can be a max of 1/60th second since a video camera captures one fields at a time.

Longer exposures probably also give you more latitude to play with the aperture, hence more depth of field, contrast, etc.

Or maybe people just like the fast-jerkiness that 3:2 pulldown creates.

[BJ_M]

Is it ever possible to watch 24P DV loaded into your computer played back in true 24P on your computer monitor?

I don't think there are any monitors that can scan that slowly. You wouldn't want to watch at true 24p anyway -- it would flicker like crazy. Note that even film movies in theaters are show at 48p -- each frame is displayed twice.

Assuming your system is set up to switch frames during vertical blanking, what happen is the frames are repeated to get as close as possible with the refresh rate of the monitor. For example, if you set the monitor to 72 Hz refresh you will see each frame 3 times. At 60 Hz some frames will repeat 2 times, some 3.

If your system doesn't wait until vertical blanking to switch frames you will see a torn image where the top part is from one frame and the bottom is another.

there are and we use them .... they are for on screen use and are sync'd to the shutter ... they are 48 or 24fps ....

then special playback projectors are used in some locations for dailys ... modified to match a 2 blade film gate or could match a 3 blade i suppose ..

sonys 950's use ussually 1/48 sec shutter speed to match the film blur look on pans - though nowdays , some directors are getting away from this (thank goodness)

[ribac]

Off the topic.
What's the benefit of shooting in 24p except out for film??
I have Panasonic NV GS400 which supposed to shoot in 24p.
But my camera is PAL (so 25f).So is there actually benefit for just output to DVD??