Puzzled about Frame mode viewing.. at DVinfo.net

Dan Uneken · May 1st, 2003, 05:38 AM

Hi!

If I shoot in frame mode on my XL-1 I get 25 entire frames a second.
When I watch this footage on a monitor, does the frame get repeated twice? Does it get interlaced again by the TV?
To be honest, I like pans better shot on normal 2-field mode than on frame-mode. Looks like PAPAPAPAPAPA in frame mode, if you know what I mean.

I believe that in the cinema they also project each frame twice, because the human eye needs about 50 flashes per second to get the impression of continuous movement....

Thanks,

Dan.

Rob Lohman · May 1st, 2003, 10:34 AM

If you shoot in frame mode make sure to use a shutter of 1/50th.
This should reduce your stutter. An interlaced or progessive
signal are exactly the same from a TV point of view. The only
difference is when the image was created (with interlaced one
half of the picture is slightly later in time than the other). Your
TV will not alter the picture or something. Ofcourse it might look
different because the timing of the pictures is different when it
is being recorded/captured.

Cosmin Rotaru · May 2nd, 2003, 04:50 AM

I don't think in cinema they project each frame twice! :) Is just that it stays longer on the screen... If you cut it down to a very small fraction of time, on the TV screen you have just one pixel at a time, but you have the entire pic on the cinema screen.

Dan Uneken · May 2nd, 2003, 08:50 AM

The shutter in a film projector has two openings, on opposite sides of the circular plane, effectively projecting the image twice.

The human eye needs 48 interruptions per second to give a satisfactory illusion of continuous movement, hence 24 fps, projected twice.

Source: The focal encyclopedia of photography.

Peter Moore · May 3rd, 2003, 10:59 AM

With projection, the picture is not constantly "refreshed" like with a CRT, so the images don't need to be doubled. They are solid and constant. The only thing that would affect the eye's perception of movement is how fast the image changes, i.e. 24fps v. 60fps.

Dan Uneken · May 3rd, 2003, 02:21 PM

Take a look inside a film projector

Robert Knecht Schmidt · May 4th, 2003, 11:43 PM

Dan's correct, by the way--commercial film projector shutters, like those you'll find in the projectors at your cineplex, complete two cycles for each frame of film, which helps to reduce perceived flicker.

Digital Micromirror Device (DMD) chips as found in DLP projectors cycle in the MHz range!

May 1st, 2003, 05:38 AM	#1
Dan Uneken Major Player Join Date: Sep 2001 Location: Andalucia, Spain Posts: 301	Puzzled about Frame mode viewing.. Hi! If I shoot in frame mode on my XL-1 I get 25 entire frames a second. When I watch this footage on a monitor, does the frame get repeated twice? Does it get interlaced again by the TV? To be honest, I like pans better shot on normal 2-field mode than on frame-mode. Looks like PAPAPAPAPAPA in frame mode, if you know what I mean. I believe that in the cinema they also project each frame twice, because the human eye needs about 50 flashes per second to get the impression of continuous movement.... Thanks, Dan. __________________ Film & TV locations & production Spain http://www.fotofilmvideo.com/

May 1st, 2003, 10:34 AM	#2
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	If you shoot in frame mode make sure to use a shutter of 1/50th. This should reduce your stutter. An interlaced or progessive signal are exactly the same from a TV point of view. The only difference is when the image was created (with interlaced one half of the picture is slightly later in time than the other). Your TV will not alter the picture or something. Ofcourse it might look different because the timing of the pictures is different when it is being recorded/captured. __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

May 2nd, 2003, 08:50 AM	#4
Dan Uneken Major Player Join Date: Sep 2001 Location: Andalucia, Spain Posts: 301	The shutter in a film projector has two openings, on opposite sides of the circular plane, effectively projecting the image twice. The human eye needs 48 interruptions per second to give a satisfactory illusion of continuous movement, hence 24 fps, projected twice. Source: The focal encyclopedia of photography. __________________ Film & TV locations & production Spain http://www.fotofilmvideo.com/

May 3rd, 2003, 02:21 PM	#6
Dan Uneken Major Player Join Date: Sep 2001 Location: Andalucia, Spain Posts: 301	Take a look inside a film projector __________________ Film & TV locations & production Spain http://www.fotofilmvideo.com/

May 4th, 2003, 11:43 PM	#7
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	Dan's correct, by the way--commercial film projector shutters, like those you'll find in the projectors at your cineplex, complete two cycles for each frame of film, which helps to reduce perceived flicker. Digital Micromirror Device (DMD) chips as found in DLP projectors cycle in the MHz range! __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

May 2nd, 2003, 04:50 AM	#3
Cosmin Rotaru Major Player Join Date: Feb 2003 Location: Romania, Timisoara Posts: 453	I don't think in cinema they project each frame twice! :) Is just that it stays longer on the screen... If you cut it down to a very small fraction of time, on the TV screen you have just one pixel at a time, but you have the entire pic on the cinema screen.

May 3rd, 2003, 10:59 AM	#5
Peter Moore Trustee Join Date: Oct 2002 Location: Arlington VA Posts: 1,034	With projection, the picture is not constantly "refreshed" like with a CRT, so the images don't need to be doubled. They are solid and constant. The only thing that would affect the eye's perception of movement is how fast the image changes, i.e. 24fps v. 60fps.