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Re: Electronic Cinema



>Rod Sommerich wrote:
>
>>I dont know about others but I am constantly irritated by a stuttered
>motion in
>>what should be smoth pans in cinema.  I can only attribute this to
>electronic
>>enhancement in the post phase of production.  In particular You've got mail
>had
>>a severe problem when I saw it at the cinema.  I could not understand why
>this
>>happened, any comments.
>


Well, the amount of motion blur is a function of not just the frame rate
but also the shutter angle in the original camera. A wide shutter angle
increases the exposure time of each frame thus increasing the motion blur
which tends to smooth out the judder caused by the slow temporal rate of
24fps. The total exposure of each frame (shutter blade angle plus lens
aperture plus amount of light on the set or shoot) is decided by the DP to
control the amount of light getting to the film. Sometimes shutter angle is
compromised to allow for television monitors to be in the picture.
Sometimes sychronous strobe lighting will be used to make each frame very
sharply resolved and this will make motion judder very obvious. I can only
assume that this would be done so green screen or blue screen mattes are
cleaner but perhaps one of the DP lurkers could answer this one. What are
the factors a DP takes in to consideration when deciding how much motion
blur is needed or desireable? I know that most CGI for film incorporates
motion blur when rendering moving images to make them more realistic. This
has been around at least since Jurrasic Park.

Another point here;  Judder of this sort will not inherently change with
electronically displayed cinema as the same factors will come in to play;

1.	Frame rate of the original taking device whether it is Electronic
Camera or OCN
2.	Exposure period of each frame
3.	Type of lighting in use

Screen flicker (different from motion judder) should be considerably
reduced with light valve displays since the display is "always on" unlike
film projection which must block the light and go dark while the film is
pulled down to the next frame.

And yet another point;  There was a reference to "motion artifacts" a few
entries ago in certain electronic displays. If these are temporal artifacts
caused by the film frame rate and exposure period then that is not caused
by the display but rather by the source material.  However, I have seen
certain artifacts with DLP projection which are caused by the mirrors
flipping up and down to pulse width modulate the amount of light from each
pixel.  This shows up as an artifact but only if your eye is scanning the
image and your focal center point is moving across the image.  You will
notice a texture in the image that disappears as soon as your eye stops
moving.  I understand that TI have improved this artifact enormously but
haven't had the opportunity to see it for myself recently (we were somewhat
busy at NAB and didn't get a chance to see much other than our own booth).
Perhaps someone from TI  would like to comment on this?

Best regards
Dave

Dave Corbitt
Engineering Support for Innovation TK
15 Garfield Ave.
Madison, NJ 07940
USA

ph (973) 377-2017
fax (973) 377-1741
Cell (973) 714-2322
e-mail  <dfc47 at earthlink.net>
http://www.innovation-tk.com/



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