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-   -   Puzzled about Frame mode viewing.. (https://www.dvinfo.net/forum/techniques-independent-production/9171-puzzled-about-frame-mode-viewing.html)

Dan Uneken May 1st, 2003 05:38 AM

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.

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!


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