drchrisbarrett <drchrisbarrett@xxxxxxxxxxxxxxxxxxxx> writes:
> As I understood the statement from olympus, it was that 35mm format
> lenses could not be used with CCD chips as the angle of the rays was to
> oblique for the imaging elements to detect.
>
> I disagree with this because:
[...]
> 4 The explanation implied that the problem is greater for wide and super
> wide angle lenses. It is indeed true that a lens with a focal length
> shorter than standard, and therefore sitting closer to the film plane,
> would indeed generate rays with shallower angles at the film plane then
> the equivalent standard lens. However, SLR wide angle lenses are not of
> shorter focal length. They are what is known as a retro-focus design
I agree that the bit about wide-angle lenses is a bit of a red herring,
given the retro-focus nature of most SLR wide-angles. However, the fact
remains that *all* of the digital backs that you can get for conventional
film cameras do not cover the full area of the film. The various digital
versions of 35mm SLRs do not have a 24x36mm CCD sensor, and they typically
increase the effective focal length of a lens by 50%.
You can get CCD sensors that cover a 35mm negative, but only for medium
format backs, where the true film size is 60x45 or 60x60mm.
I can only assume that the reason why all these digital backs don't cover
the full film area is because they cannot cope with the shallow angles of
the incoming light at the edges of the film.
Alasdair
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