Yes - come to think, one would hardly expect a conversion right down to
f17.5 to work very well. I will put in another post to ask whether any one
has experience of the Canon tele converter.
Thanks again
Peter
"NJH" <> wrote in message
news:m0Izb.3327$ m...
>
> "Peter Billinghurst" <> wrote in message
> news:bqn70f$ru8$...
> > Many thanks for this - Canon do advertise such a converter on their web
> > site. Also several other accessories for the G3.
>
> Yes, I checked their site and see that under G3 accessories they list both
> wide-angle and tele converters. Unfortunately the site doesn't give the
> magnification of either. But the usual thing from other camera
manufacturers
> for a wide-angle converter is 0.8x, and I presume that Canon's is about
the
> same. I suspect that is about as much as can be done (as far as getting a
> wider angle goes) with this type of supplementary lens without degrading
> optical performance in one way or another.
>
>
> >
> > I do actually have both converters, but made by an outfit named Digital
> > Optics. While the glass seems to be very good, the magnifications or
> > conversion factors are nothing like x.5 or x2 as advertised: more like
..77
> > for the wide angle and 1.2 for the telephoto. I am just checking on the
> > facts before complaining!
> >
> > Once again thanks
>
> You're welcome. I'm not surprised that the w.a. converter doesn't come
close
> to the advertised magnification, but it is surprising that the tele
> converter falls so far short. Interesting.
>
> Neil
>
>
> >
> >
> >
> > Peter
> >
> >
> >
> > "NJH" <> wrote in message
> > news:bAwzb.37429$. com...
> > >
> > > "Peter Billinghurst" <> wrote in message
> > > news:bqll5m$n4q$...
> > > > Canon advertises x.5 and x2 lenses for the Powershot G3. What does
> this
> > > > mean? Would it be correct to say that a x.5 lens will double the
> > > dimensions
> > > > (both width and height) of the area pictured and the x2 lens would
> halve
> > > the
> > > > dimensions?
> > >
> > > Yep, if those really are the magnifications of the supplementary
lenses.
> > For
> > > a rectilinear lens, the ratio of focal length to film (or sensor)
> > dimensions
> > > is the same as the ratio of distance to subject dimensions, as you
have
> > > probably surmised.
> > >
> > >
> > > >
> > > > Or to put it another way, what effect do these lenses have on the
> focal
> > > > length of the lens? I assume that 35mm would become 17.5mm with
wide
> > > angle
> > > > and 140mm would become 280mm.
> > >
> > > That's correct, if the converter lenses really do alter the focal
length
> > of
> > > the prime lens 0.5x and 2x respectively. That's not so difficult for a
> 2x
> > > add-on lens, but it's quite a feat for a wide-angle converter to give
> > 0.5x.
> > > There are many so-called 0.5x converters sold that aren't really that
by
> a
> > > long shot. If it's a Canon-made lens advertised that way I'd presume
it
> is
> > > correct, but are you *sure* these advertised converters originate with
> > > Canon?
> > >
> > >
> > > >
> > > > Any advise would be welcome. Thanks
> > >
> > > I would first of all make sure who made those lenses you're talking
> about.
> > > Frankly I would be very surprised if Canon made an 0.5x converter for
> the
> > > G3.
> > >
> > > Neil
> > >
> > >
> >
> >
>
>
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