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This topic comprises 5 pages: 1 2 3 4 5
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Author
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Topic: Sony exhibiting Da Vinci Code in 4K
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 06-02-2006 10:18 AM
In my opinion jitter and weave are much less of a problem than scratches--here's why:
We are conditioned to notice changing phenomena, not fixed phenomena. Jitter/weave manifest as a certain kind of unsteadiness, but it is a continuous unsteadiness that is always there in the background, and you can tune it out. It does not "come and go."
Scratching, in general, is most noticable and apparent because it changes. A single black line that holds its position perfectly is far less annoying than a single black line that comes and goes every frame. Similarly, scratches whose color changes (because depth changes) or position changes (platter scratches) are much worse.
Similarly, CAP codes are really bad because they are sudden. (I wonder what it would be like if CAP codes faded in and faded out over a 10 second period. Hrmm...)
I must say, I'm not impressed when film people go around evaluating presentations and claiming they are "rock steady." For film, that's never true (of course it is true for digital). The question is really how jumpy it is in each direction, and to evaluate that, you need a measurement, i.e. from the RP40 checkerboard).
[hmm. That would be a great use for "cheap" test film. No need to worry about the registration, as long as the magnification didn't change, it would be useful. High-speed contact printing, 30c/foot, here we come!]
--jhawk
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 06-03-2006 11:00 AM
quote: John Hawkinson
We are conditioned to notice changing phenomena, not fixed phenomena. Jitter/weave manifest as a certain kind of unsteadiness, but it is a continuous unsteadiness that is always there in the background, and you can tune it out. It does not "come and go."
Exactly. We mustn't underestimate the power of the human eye/brain system in removing extranious information and compensating for what it has learned is unnecessary and possibly distracting changes. White-level compensation is a remarkable example of how we correct for changes in the environment in away that makes them nearly transparant. Same with geometric distortion -- we can sit to the left and right side of the screen. In absolute terms, the picture is skewed and geometrically distorted, but our visual compensitory system says, ok, this is the steady-state for this image. You will only take a moment or two for the distortion to fade and for the picture to look "normal" to you.
Try this -- remove the anamorphic lens and watch a scope film for a reel or two. Although you see the compressed image with people compressed and skinny, it will shortly become more of something that can be intellectual acknowledged, rather than something that cannot be tolerated. Now put the anamorphic lens back in -- everything will look wrong....people will look fat even thought in absolute terms, the image is correct. It will take time for your compensation mechanism to "turn off." Nothing in our perception is "absolute."
In real life, your head is bobbing and weaving all the time; shake your head from side to side, what you see remains steady --it's your eye/brain system constantly correcting for extranious information. You drive your car, jitter is a constant, yet you are able to tune it out so effectively that you hardly notice it is there. Put a camera in that same spot and record what it sees without compensation, i.e., an absolutely correct record of what you see, and you will quickly appreciate how sophistocated our ability to "normalize" the perception of our environment really is.
Rock-steady, then, is much overated, unless of course you are watching UNITED 93 -- then your eye/brain just gives up and tells your stomach to punish you for taking them all to this movie.
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Christopher Seo
Jedi Master Film Handler
Posts: 530
From: Los Angeles, CA
Registered: Jun 99
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posted 06-08-2006 01:23 PM
Lyle, your point about when each frame starts and ends is an interesting one. Assuming the frequency of each mirror turning on and off remains constant through a single frame, any sudden change in that frequency could signal to our eyes' light receptors that a change has occurred. I suppose it really depends on the precise physiology of how the eye integrates such rapid light flashes.
As for the term "rock steady", I agree that it is often used too loosely, but I also think that a valid, rigorous definition for film could be formulated. For example, one could define a "rock steady" film image, based on 35-PA, as one in which the movement due to jump and weave is less than the distance between lines in the highest resolvable line pair. Such a definition would take into account all factors in presentation except for the minimum screen distance of the viewer, which could be added in as well.
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