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Old Dec 13, 2007, 6:26 PM   #1
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For farts and giggles I did some tests comparing my new AHD against a Panasonic HVX200.

Firmware 1.600

http://emrl.com/j/projects/AHD/

Just stills for now. I'll post video once I get it rendered.

Enjoy,

-Jay
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Old Dec 20, 2007, 9:56 AM   #2
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Thanks Jay, I was wondering about ChromaKey... Although I still have my 3CCD Panny GS-120 I'll probably use for it.
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Old Dec 20, 2007, 2:14 PM   #3
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cinejay wrote:
Quote:
For farts and giggles I did some tests comparing my new AHD against a Panasonic HVX200.

Firmware 1.600

http://emrl.com/j/projects/AHD/

Just stills for now. I'll post video once I get it rendered.

Enjoy,

-Jay
Interesting :G So which bitrate will you be using for video comparison? I understand you can go upto 100Mbps with this camera!
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Old Jan 3, 2008, 6:37 PM   #4
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Yes, it was 100mbps.



BTW, I uploaded some videos of the test if anyone is interested.



-Jay
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Old Jan 3, 2008, 7:58 PM   #5
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This is good stuff, the kind of thing most people don't bother to test. However, I would point out that the reason for the image skew on panning with the A-HD is not because it is a CMOS sensor. A CCD can do the same thing. For example, the Go-HD has a CCD as well as many of the logitech quick-cams. Yet, they suffer from the same issue. I've narrowed the problem down to the way in which the imager is accessed by the CPU. If it is accessed over some kind of serial data-transfer, then the communication is too slow. It makes the design easier, cheaper, and quicker to impliment, also allowing the designers to change the imager at the last minute or even during production. The way the imager should be read is on the CPU memory bus. Essentially, an imager is designed like a memory chip. It has address lines and data lines. The CPU fethces the information from a particular pixel in the same way that it would from an SRAM or DRAM chip. This method is much faster but requires a higher level of integration of the chip and CPU bus.
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Old Jan 4, 2008, 12:13 AM   #6
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If I take video sideways out the window of a car, of, say, a bridge railing with vertical posts, the posts appear very slanted on the resulting video. Is this due to exactly the same issue?
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Old Jan 4, 2008, 7:23 AM   #7
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Quote:
If I take video sideways out the window of a car, of, say, a bridge railing with vertical posts, the posts appear very slanted on the resulting video. Is this due to exactly the same issue?
Yes. Essentially the posts are in one place when the imager starts sending the top part of the frame, and the posts have moved to a different place by the time the frame is finished. You can see the progression of this all the way down the frame, hence, a bent-looking, slanted, or skewed image.

Things that are moving up and down in the picture (or an up-down pan) causes a different problem. Moving the camera down causes the entire picture to be "compressed" or "squeezed" looking where moving up causes it to expand.

One thing I've noticed is that the effect is lessened on cameras with a higher frame-rate (such as the A-HD which achieves a real 30 fps.) It is worse on cheap cameras that only do 10 fps.

As annoying as the problem is, and we've all discussed it on here before, it is possible to learn how to shoot video on these types of cameras and make this effect almost unnoticeable. The biggest thing is to hold the camera still or put it on a tripod.
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Old Jan 28, 2008, 7:11 PM   #8
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Jay,

Thanks for all of the info. Could you:

1. Some of the images are self-explanatory, but could you provide a liitle commentary on the waveform and vectorscope graphics?

2. Also, could you provide a still shot of the resolution charttaken bythe A-HD in camera mode. Basically, trying to see how much degradation occurs because of the compression.

Thanks again.


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