Patent: Video from Digital SLRs at

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Old April 6th, 2008, 11:50 AM   #1
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Patent: Video from Digital SLRs

"In order to operate at 30 frames per second (the video capture speed called for in Teradaís patent), the mirror would have to bounce up and down 3 times faster than the rocket-fast Canon EOS 1D Mark III. Clearly, thatís not a desirable (or quiet) way to do video on a DSLR.

The patent calls for a mirror that remains in the path of light. Itís a special mirror though. It reflects 30% of the light and transmits 70% of the light, allowing the light to make its way to the image sensor without moving anywhere."

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Old April 6th, 2008, 12:07 PM   #2
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Too much prior art. The magic mirror is nothing but a beam splitter, already used in the classic Pellix 35mm camera. The beam splitter routed some of the light to the viewfinder, and let the rest fall on the film plane. One of the quietest 35mm cameras I ever used, no flopping mirror.

Besides, how do you think they split the light to 3 CCD's in 3-CCD camcorders? Beam splitters.

Don't think a patent would survive a serious legal challenge.

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Old April 6th, 2008, 12:39 PM   #3
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Lots of patents rely on prior art for part of their approval. My take on the article is that his Automatic Focusing algorithm/program is the NEW technology. This is the kernel of his patent, not the mirror - which as you correctly pointed out is 'old school' cine gear.

I think the article is not very clear, but it seems as if he's developed a program that will sense the different mode, and apply some sort of auto focusing correction that will prevent the lens from hunting and 'breathing' while shooting in cine mode. At least, that's what I took away from it.
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Old April 9th, 2008, 10:31 PM   #4
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Martin is correct; the Pellicle Mirror concept is nothing new even to still cameras.

In the late 80's Canon produced the EOS RT and later the EOS 1n RS which both had the pellicle mirror. The viewfinders in both cameras were darker than standard-mirror cameras and weren't widely received by the full-time pros who it was marketed for, but did find a home partly with wedding and event shooters who wanted a nearly-silent SLR for their work.
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