----- Original Message -----
From: "drchrisbarrett" <drchrisbarrett@xxxxxxxxxxxxxxxxxxxx>
> Dear Mr Ling (sorry I don't know the best way to address you),
>
You can call me CH.
>
> Your point about the Nikkor 105 on a 1/2" CCD is valid. It will only
> image the central portion of the image.
>
> However, its is not the core of my argument:
>
> Even in this case, the 1/2" CCD images rays emerging from the whole of
> the rear element of the lens (but obviously not all since some fall
> outside its area). I don't know what the rear element diameter is, but
> it will be large enough to give similar angles to those in my table.
>
The further the light beam deviated from the center the larger the angle,
Olympus also mentioned the normal lens design mainly affect the light fall
to the edges of the CCD not center. If your CCD is 640x480 the size may be
even only 1/3", the angle will be too small to cause problem.
> I don't know what you mean by a specially designed perpendicular lens
> for a video CCD. With the lens to CCD distances they use on video
> cameras, and the f numbers they obtain, they must be using largish rear
> elements relatively close to the CCD. The onlt way to "design" a lens to
> give almost perpndicular rays at the CCD is to design it with a very
> small rear element a long way from the CCD plane.
>
I'm not sure about your statement "small rear element a long way from CCD"
is need to reduce the angle is true or not, I just know Olympus claim they
design the E-10's lens with light perpendicular to the CCD. They have a rear
element larger than the CCD NOT smaller, sorry!
> If non perpendicular rays are a fundamental problem with the Fuji
> Finepix, then the same effect of color shifts across the image will also
> occur with a video chip. The resolution of the chip is not an factor.
>
Actually if a CCD of around 1/3" (I think most video CCD is at that range),
with a 640x480 pixel, the pixel size will be large enough to accept some
light coming with an angle. A CCD of 1/2" with 2M pixel like the Olympus
C2000 will have much smaller CCD pixel size, it will have much more problem
than a large pixel CDD element, that's the relative surface area vs deep of
the pixel that count, I hope you understand what I mean.
C.H.Ling
> Hope this helps.
>
> Chris
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