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Posted by Jan Panteltje on 11/09/07 12:20
On a sunny day (Fri, 9 Nov 2007 02:12:08 +0000 (UTC)) it happened
davem@cs.ubc.ca (Dave Martindale) wrote in <fh0flo$gup$1@swain.cs.ubc.ca>:
>Jan Panteltje <pNaonStpealmtje@yahoo.com> writes:
>
>>It is a bit more complicated then that.
>>This camera, the HV20, is a single sensor chip model.
>>To get color, the chip's sensor elements are covered by red, green, and blue
>>filters:
>> http://en.wikipedia.org/wiki/Bayer_filter
>>Likely Bayer patterns (as Canon mentions 'simple RGB' in their specs).
>
>>Just this fact, in itself, sort of reduces the luminane resolution by
>>half the horizontal pixels, see:
>> http://www.cambridgeincolour.com/tutorials/sensors.htm
>
>No, that's not correct. A Bayer-sensor camera is able to achieve a
>*luminance* resolution that is comparable to a monochrome camera with
>the same number of pixels, not half.
Very slightly better, if you also use the 'in-between' method,
as pointed out in that link.
A white spot of size 2 pixels wide (just looking in H for simplicity)
will also be 50% over the previous, and 50% over the next 2 Bayer elements.
spot
[]
RGRGRGRG sensor filters
-- -- --
B
-- --
A
'Spot' in this case is over pixel 2 G, and pixel 3 R, and combining 2 and 3 in A
gives 100%.
But it is also over the pixel 2 in the pair pixel1 pixel2, giving output
there, and over pixel 3 of the pair 3,4, giving output there, resulting in
__ 100%
-- 59%
-- 30%
--------------- 0%
(Green is more then red).
While it should have been:
-- 100%
--------------0%
>The reference you point to even
>says that you can do better than half resolution in demosaicing.
'A little better', as the above example shows.
>In the digital still camera world, which I'm more familiar with, a 6
>megapixel camera with a sensor that's about 3072x2048 pixels can resolve
>nearly 2000 tvl per picture height - not the half-resolution 1000 that
>you suggest.
If you say so... :-)
Did you notice the HV20 only has
http://images.camcorderinfo.com/images/upload/Image/Canon/Canon%20HV20/Video_Performance/3000lux/Canon_HV20_3000lux_24P_vivid.jpg
quote:
In 1080i, the HV20 showed a vertical resolution of 575 lw/ph and a
horizontal resolution of 625 lw/ph. In 24P, the camcorder actually
improved the vertical resolution, producing less break-up and
artifacting in areas of high-density information, boosting the vertical
resolution up to 600 lw/ph. The horizontal resolution remained unchanged
at 625 lw/ph.
^^^^^^^
end quote.
Now that is including the lens, but a good reality check I'd say.
See also the 600 vertical, and this is for the 1920x1080 sensor.
In YOUR theory, you's get 1000 lines vertical, and >1500 horizontal.
Now that is clearly not the case, and I bet Canon would have LOVED to do it,
if they could.
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