Quote:
Originally Posted by EricB
Thanks Malcolm. So the ideal CCD camera would be high resolution and would have a high frame rate per second.
I have noticed that the high resolution DSK cameras ($649) only have 15 frames per second, as opposed to 60 frames per second for the cheaper lower resolusion ones ($379). Why the difference?
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The difference is bandwidth basically.
If you double the resolution horizontally and vertically, you quadruple the amount of data that needs to be transferred.
So 640x480 = 307,200 pixels per frame
1280 x 960 = 1,228,800 pixels per frame
Uncompressed that is (roughly) 0.92MB per frame vs 3.7MB per frame
so for the same bandwidth, you can capture 4 times as many frames in 640x480 as you can at 1280x960
These figures assume 8 bits per pixel for each Red, Green and Blue channel, or 24bit colour as it is sometimes called)
To capture 60 frames per second at 1280 x 960 uncompressed would be about 216 Megaytes per second!
USB 2.0 has a maximum theoritcal transfer rate of 60MB per second, it is slower than this in reality due to overheads, but you can see that for uncompressed data, 15fps at 1280x960 = 54MB/s which is as fast as USB2.0 can go.
Of course, compression can allow faster data rates, but the same principle applies, if you quadruple the amount of pixels, and the bandwidth is fixed, you end up with 1/4 the frame rate.