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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old September 17th, 2009, 01:43 PM   #16
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I've just figured out how to make the 5D continue to output 1080i while recording.
Well that blows my theory about needing the second chip to do this - I wonder what the second chip does in the 7D? Do you have any way to monitor processor load or temp? I wonder if running full res will tax the system beyond some level that Canon is comfortable with.
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Old September 17th, 2009, 01:54 PM   #17
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I wonder what the second chip does in the 7D?
I believe that its main function is to enable high-speed continuous shooting of 8 images per second. It's possible that it's needed for 720p60 encoding, but I'm not sure. (I doubt it.)

Two processors are definitely not needed for 1080p24, since 24p is slower than 30p. The 5D2 might have a hardwired clock that makes it impossible to upgrade to 24p with firmware alone, but it definitely doesn't need another processor to go slower.
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Old September 17th, 2009, 02:19 PM   #18
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I believe that its main function is to enable high-speed continuous shooting of 8 images per second. It's possible that it's needed for 720p60 encoding, but I'm not sure. (I doubt it.)

Two processors are definitely not needed for 1080p24, since 24p is slower than 30p. The 5D2 might have a hardwired clock that makes it impossible to upgrade to 24p with firmware alone, but it definitely doesn't need another processor to go slower.
This brings up a question about which I have not expertise. I remember days of overclocking motherboard chips, how about the idea of slowing the clock in the camera to get defacto 24p even though the chip thinks it running at 30p.?
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Old September 17th, 2009, 04:01 PM   #19
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I wonder what the second chip does in the 7D? Do you have any way to monitor processor load or temp? I wonder if running full res will tax the system beyond some level that Canon is comfortable with.
My guess is the same as Jon's -- the higher frame rate modes require a faster scan of the chip. This will also reduce jello if the sensor can be scanned in 1/80th of a second rather than 1/40th.

I'm not very confident that we'll be able to do much with a windowed read of the sensor. In LiveView mode the noise goes up dramatically while reading a small section, which makes me think that either the NR algorithm requires the entire scanline, or that reading a small section quickly requires the ISO to be bumped temporarily.
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Old September 17th, 2009, 08:35 PM   #20
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NR algorithm requires the entire scanline, or that reading a small section quickly requires the ISO to be bumped temporarily.

hahaha Tramm, i love reading your posts... I don't understand them but i love it that someone does AND is doing something about it!

On behalf of everyone, thank you!
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Old September 17th, 2009, 08:44 PM   #21
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tramm,

just like modern TVs modulate scan line frequency to improve picture quality, does the 5/7D adjust cmos scanning frequency to compensate for different shutter speeds?

i.e.: if the shutter speed is set to 1/40 will the camera scan slower than say if the shutter speed is set to 1/80?
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Old September 18th, 2009, 02:19 AM   #22
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The 5D2 takes 1/40 seconds to scan the sensor, regardless of the shutter speed. This means that we get the same rolling shutter no matter what adjustments we make to the camera controls.

Unfortunately, the sensor scan time is quite unlikely to be improved by firmware. The only good news is that it forces us to get better stabilization gear, which helps us make better films. :)
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Old September 19th, 2009, 05:25 PM   #23
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Do we know the scan time for the 7D?
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Old September 20th, 2009, 11:11 AM   #24
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Do we know the scan time for the 7D?
Not yet.

All we need is for somebody with a prototype to film some flashes at about 1/40 shutter. Then we need to see three full-res screenshots

(1) With the entire flash captured within a frame,
(2) with some of the the flash captured in the bottom lines of a frame, and
(3) the frame immediately after (2) with the end of the flash captured at the top of the frame.

Tell us your frame rate, count the lines, and you can find out the shutter speed, the time between scans, and the time to scan the sensor.

Hopefully, it's faster than the 5D2. If Canon were to update the 5D2 to cover 7D frame rates, the two bodies would make a killer pair. (As of now, they have no common frame rates.)
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