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Old January 10th, 2005, 02:11 AM   #31
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I think that a fair comparison between 1ccd and 3 ccd would be 4/3" 4Mp vs. 3x2/3" 2 Mp.
With these you get same resolution, pixel size and amount of light per pixel.
I would guess that single 4Mp chip is cheaper than three 2Mp's plus prism.

Only problem I see with bigger imager size is that there's no fast zoom lenses available.
Why is this?
Can someone elaborate?
Is it just that eg. with eng lenses picture quality is so bad with f1.8, that there is now such zoom lenses with 35mm imager?
(Panavision has a zoom with T2.3 but that's about it...)

If you want fast zoom, lets say 10x with f2, is the imager size limit really 2/3" and why?

As a far future dream would be that camera has a big imager with so much resolution and sensivity that in low light conditions one could just use a portion of the imager and faster lens...
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Old January 10th, 2005, 04:19 AM   #32
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<<<-- Originally posted by Toke Lahti : ... Well, isn't there same color filters in front of 3ccd block's cells than in front of 1ccd cell's pixels? Or how else green ccd gets only green etc.? -->>>


Some surfaces of the prism has a number of coating layers that let only certain wavelengths to pass based on interference (dichroic mirrors). The rest of the spectrum is bounced back and continue its way to the other CCDs. This is a more efficient way of utilising the incoming light than with a bayer filter where the unwanted portion of the light is just lost in the filter.
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Old January 10th, 2005, 04:54 AM   #33
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<<<-- Originally posted by Gabriele Sartori : "VERY IMPORTANT though, a similar implementation (and losses) assumes that no pixel shifting is present hence a 3CCD 2MP (per CCD) camera will have a maximum resolution of 2MP not 4, not 6. It will be more sensitive to the light though.
As I said, you can't have it both way. -->>>

I don't see a reason why you could not use pixel shifting and still taking advantage of the better sensitivity of 3CCDs. By pixel shifting you can increase the resolution and still the amount of light per pixel remains the same.

One interesting camera is the JVC 8Mpixel camera that uses 4 2MPixel CCDs (a red, a blue and two green). It uses pixel shifting in both the horizontal and vertical direction. The resulting pixel color arrangement and number is quite similar to a single 8MPixel bayer sensor. So the resolution you can produce is about the same. Still the individual pixels get more light with the pixel shifted camera.
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Old January 10th, 2005, 09:25 AM   #34
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I'm not sure if we should move this conversation under the topic " I don't believe 3-CCDs are needed anymore", but I'd like to question that is dichroic prism somehow more efficient than bayer filter?

Here's a nice illustration of 3ccd block:
http://en.wikipedia.org/wiki/Dichroic_prism

Let's take as an example white light coming in.
In 3ccd first mirror bounces blue light (1/3 of the whole) and blue ccd registers it.
How does this differ from blue filtered pixel in bayer ccd, where blue filter filters 2/3 of the whole resulting 1/3 to pass?
(And we are still comparing 4/3" 1ccd with 3x2/3" 3ccd, so the pixel size is the same.)

Then a little bit more about resolution: especially if yuv sampling is used where chroma resolution is less than luminance one 4Mp is as good as three 2Mp's. How about full rgb resolution?
What are the best debayer algorithms, how do they work and how efficient they are?
What is the needed resolution for 1ccd to get same acuity than 3x2Mp with full rgb (4:4:4) signal?
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Old January 10th, 2005, 11:39 AM   #35
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<<<-- Originally posted by Toke Lahti : Let's take as an example white light coming in.
In 3ccd first mirror bounces blue light (1/3 of the whole) and blue ccd registers it.
How does this differ from blue filtered pixel in bayer ccd, where blue filter filters 2/3 of the whole resulting 1/3 to pass?
(And we are still comparing 4/3" 1ccd with 3x2/3" 3ccd, so the pixel size is the same.) -->>>


If you use a bigger lens with a bigger CCD of course you will have better light sensitivity.

But if you use a single 4/3" CCD you need to have a lens with two times the focal length as opposed to a 2/3" CCD. If you enlarge an f2.8 lens to an f2.8 lens with two times the focal length the weight increase will be 8 times. And this lens will be able to give more overall amount of light to your sensor so that your camera can catch up with sensitivity. But with a similar sized big lens a 3CCD camera would be even more sensitive.

I don't say however that if you add together the price of the imaging block and the lens the 1CCD camera will be more expensive (of course only in the case of lenses with a mild zoom range). A 2/3" prism must be expensive. A cheap single chip 4/3" video camera would be cool.



<<<-- Then a little bit more about resolution: especially if yuv sampling is used where chroma resolution is less than luminance one 4Mp is as good as three 2Mp's. How about full rgb resolution?
What are the best debayer algorithms, how do they work and how efficient they are?
What is the needed resolution for 1ccd to get same acuity than 3x2Mp with full rgb (4:4:4) signal? -->>>


There are few RGB cameras available especially with a single sensor. In the case of the Panavision Genesis they put 11.5 MPixels to generate and record a 2MPixel RGB 4:4:4 image.
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Old January 10th, 2005, 04:41 PM   #36
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<<<-- Originally posted by Balazs Rozsa: <<<-- A 2/3" prism must be expensive. A cheap single chip 4/3" video camera would be cool. -->>>

I've also understood that it is too hard to use prism with bigger chips than 2/3" or smaller pixels than hdcam's because of thermal expanding (what's the right word in english?) etc.

4/3" appears very tempting.
40-150mm F3.5-4.5 for Olympus is $280.
By adding one 0 to the price I bet it could be 15-150mm/f2.8...
Mass market is the key thing.

Canon HJ11x4.7B/T2.1 for 2/3" weights 1.6kg and costs $23k.

<<<-- There are few RGB cameras available especially with a single sensor. In the case of the Panavision Genesis they put 11.5 MPixels to generate and record a 2MPixel RGB 4:4:4 image. -->>>

Genesis' brochure says: "12.4 mega pixel, true RGB sensor (not Bayer pattern".
Whatta heck?
Of course Panavision will add resolution when they develop better ways to record it.
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Old January 14th, 2005, 01:02 AM   #37
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Slow down.
A single chip camera is equivalent to 4-chip camera with every chip having FOUR times less pixels! Two chips are green - shifted by 1/2 pixel (!!!), one is green and one is blue (shifted also). If you believe in a single chip camera resolution you have to believe in increased resolution of 3 chip camera (except for a one green - not two). Study a diagram explaining JVC chip at work. It is equivalent, at least horizontally, to the operation of shifted sensors in 3 chip cameras.
That simple,
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Old January 14th, 2005, 02:38 AM   #38
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"A single chip camera is equivalent to 4-chip camera with every chip having FOUR times less pixels!"
you are so wrong!
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Old January 15th, 2005, 12:11 AM   #39
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The other two chips are blue and red (not green - sorry).
If you ever had chance to see an enlarged ccd sensor you would find that there are spaces between active pixels. Theoretically, one could put another pixel between every two active but it is not possible in practice. Now, use a 4 way prizm, put four sensors shifted by half of pixel spacing, up, down and right, and you got an effective sensor with a double resolution, verically and horizontally. The Sony HD camera has 1080 pixels verically so only horizontal shift is needed.
Is it clear now?
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Old January 15th, 2005, 12:54 AM   #40
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Andre,
Fuji have a small pixel in between the large pixels. It can be activated for capturing a little more highlight detail:
http://www.dpreview.com/news/0301/03...superccdsr.asp
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Old January 15th, 2005, 02:38 AM   #41
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"Theoretically, one could put another pixel between every two active but it is not possible in practice"
Doesn't work like that. Probably you don't know that a CCD has an array of microlenses in order to use almost all the area from pixel to pixel. The effective active area of a Pixel is indeed smaller but almost all the area is used without space in the middle in order to catch light thanks to the microlenses. THis is true for a single CCD or 3 CCD and doesn't really leave "space in the middle" unless is done intentionally but in that case some light is lost with all the consequences......

Only in the Sigma SD9 and in the Kodak 14N photo cameras there weren't microlenses since microlenses can produce aberrations in certain conditions (using some old optics) . Both cameras have ben discontinued and reintroduced in the market with the layer of microlenses.
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Old January 15th, 2005, 04:16 AM   #42
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<<<-- Originally posted by Andre Jesmanowicz: Is it clear now? -->>>

Very clear, as it has been.
Remember that no camera uses 4ccd construction.
If you are using pixelshifting with all ccd's, resolution with this 4ccd system would be identical to 1ccd system, that uses same amount of silicon. Eg. 4x 1/3" 1Mp compared to 1x 2/3" 4Mp.
What is the benefit of having 4ccd's then?
You want to have deep DOF?

When digital cinema will reach its prime (after some decades) there might be a need for multi imager systems again. If the imagers are already big enough and one would like to have more resolution and sensivity but not less DOF.
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Old January 16th, 2005, 01:27 AM   #43
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I want nothing. It was simple explanation of how one can get increased resolution by shifting a green chip in 3 ccd cameras.
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