On Tue, 16 Jun 1998, Soenke Jansen wrote:
> WKato@xxxxxxx wrote:
> >
> > I just bought an XA with flash as a carry-around camera. I was looking at
> > the
> > tiny lens, about 1.25 cm. in diameter, and comparing it to the front element
> > of the SLR Zuiko 35m f 2.8, which has a diameter of 2.9 cm.
> > According to my calculations, over 5 times as much light hits the front
> > element of the SLR lens as does the XA. Where does it all go?
>
> Hmmm, basically it must be heating the camera!
> I'm in no way an expert, but the lens of the XA is much closer to the
> film, so less light 'get's lost' on the way there.
> OK, ok, this is a rather crude concept for something involving focal
> length, effective aperture, transmittance etc.
> Anybody with a sound explanation out there?
>
> Cheers,
> Soenke, Hamburg
>
Indeed your first explanation is very sound. The intensity of the light
decreases with the squared inverse of the distance. Furthermore, some of
the light would be scattered inside the lens boundaries and the camera,
so assuming that they are all black, it should be converted to - no matter
how small - heat. Otherwise, they would be reflected, and some of them
would escape back from the lens, and the rest would be converted to other
forms of energy to make the necessary deformation on the film to form the
image. This may be a significant cause of flare.
OMer
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