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Old November 28th, 2005, 06:08 AM   #31
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Thanks for that tip, Charles. I know I will use it and now I don't have to learn the hard way. I'll bet there is another human process that makes different rack speeds make sense. Perhaps it has something to do with the way the brain shifts attention. Maybe it shifts faster when it is more highly excited?

If there exists some sort of book called something like "The Biology of Cinematography", I would love to get a copy. I would love to know if someone has done a study on why different film techniques work the way they do for human perception.

Glenn, I really hope that you are correct. I know that blurred images take less to compress (there are greater zones of similar color/brightness) in a still image, but will it really leave more room for details in the DV compression format? I would love to know for sure. That would be an excellent side-effect.
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Old November 28th, 2005, 10:25 AM   #32
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Another thing to think about, though, is whats about the worst thing for compression? Grain. There arent many things that dehomogenize (is that a word?) an image on a fine detail level than that. So as soon as a 35mm adapter starts adding grain, it is possible it would significantly worsen the video compressor's ability to be unnoticed. And it doesnt help that the loss of light in such an adapter might cause some of us to turn up digital gain, adding digital noise, even worse for compression than (static) grain.
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Old November 28th, 2005, 10:37 AM   #33
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Charles, thanks for the tip. Those are the kinds of things that can help go a long way toward making amateur or independent or even entry-level pro filmmakers stop making such horrible-to-watch movies.

I use the term movies because "videos" makes the skin crawl, but we aren't shooting "films" around here either. ;-)

Glenn, the real question is:

Is it that a soft background leaves more room for less compression in the rest of the frame... or is it that the DV25 compression algorithms compress everything a given amount, period? For example, a JPEG compressed heavily will show an "artifacty" subject regardless of whether the background is out of focus or not.
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Old November 28th, 2005, 11:06 AM   #34
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With DV compression it is both fixed and adaptive. Yes, there are only 25Mbps to work with. How those bits are allocated is part of the compression scheme. If some areas of the image are "simple," then there are more bits left over for those areas that are "complex." Whether you achieve that simplicity through shallow depth of field or through simple set design, the effect is the same: better use of DV compression.

The adaptive quality of it holds true for black and white DV as well. Shooting black and white in-camera will result in a better image than converting to black and white in post. Since the color channels are vastly simplified, nearly all of the bits are used to create a very high-quality black and white image.

As for in-camera sharpening, nearly all cameras do it, most overdo it by default, and it is rare in non-professional cams to have any control over it. My GS400 has a slider in the menu to control sharpness. Simply turning it down results in perceptiblly shallower depth of field, because out of focus objects are allowed to stay out of focus and not sharpened up by the camera. Also simplifies the image, improving the overall quality, per my first point.

I have heard of a lot of video shooters who always use a ProMist filter to "take the edge off" their video. However, the filter is outside the camera, and while it may soften a bit, the camera generally going to defeat that effect by the excessive sharpening that it performs. It's like allowing the camera to fight against itself. A better solution is to find the sharpness or detail setting in the camera and just take it down a notch.

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