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From: Paul Furman on 24 May 2010 13:20 DanP wrote: > Paul Furman wrote: > >>> To answer that properly you need to compare 2 lenses with different >>> lens diameters _at_the_same_aperture_ (f number). >> >> You're using the wrong terminology. When you say lens diameter, I think >> you mean maximum aperture. > > I am talking about lens diameter Lens diameter doesn't necessarily mean anything, particularly for wide angle lenses. Aperture or more specifically f/stop (factoring in focal length) is the issue. > measured in inch/mm. > I have started this thinking if miniaturisation of lens has any bad > points. > > You have answered that, bigger lenses will have a bigger aperture > (lower f number) and I understand that there is no other optical > advantage.
From: Peter on 25 May 2010 20:24 "Paul Furman" <paul-@-edgehill.net> wrote in message news:K5adnfybisEPdGTWnZ2dnUVZ_jKdnZ2d(a)giganews.com... > Ray Fischer wrote: >> Paul Furman <paul-@-edgehill.net> wrote: >>> Ray Fischer wrote: >>>> DanP <dan.petre(a)hotmail.com> wrote: >>>>> On 23 May, 18:50, rfisc...(a)sonic.net (Ray Fischer) wrote: >>>>>> DanP <dan.pe...(a)gmail.com> wrote: >>>>>>> On May 23, 3:31 am, rfisc...(a)sonic.net (Ray Fischer) wrote: >>>>>>>> Wrong. Bigger apertures allow higher resolution. That's why big >>>>>>>> telescopes are better than tiny ones. >>>>>>> Telescopes are focused at infinity so that is a different case. >>>>>> ?!? >>>>>> >>>>>> Why is that different? >>>>> Because their optics are fixed >>>> Nope. >>>> >>>>> and you want the biggest lens/mirror >>>>> you can get. >>>> Because bigger means higher resolution. >>> I think it's because telescopes have very large focal lengths so the >>> aperture needed to avoid diffraction becomes very large. >> >> I think that you're not making sense. > > What's wrong with the explanation? Take a 4 inch telescope (100mm > aperture) with a focal length of 1000mm, that's f/10, hardly a fast lens. Some people will argue for purposes other than sharing knowledge. -- Peter
From: John Navas on 28 May 2010 10:55 On Tue, 25 May 2010 20:24:19 -0400, "Peter" <peternew(a)nospamoptonline.net> wrote in <4bfc6aca$0$7705$8f2e0ebb(a)news.shared-secrets.com>: >Some people will argue for purposes other than sharing knowledge. Now there's an eye opener! LOL
From: Ray Fischer on 29 May 2010 01:55 Paul Furman <paul-@-edgehill.net> wrote: >Ray Fischer wrote: >> Paul Furman wrote: >>> Ray Fischer wrote: >>>> Paul Furman wrote: >>>>> Ray Fischer wrote: >>>>>> DanP wrote: >>>>>>> Ray Fischer wrote: >>>>>>>> DanP wrote: >>>>>>>>> Ray Fischer wrote: >>>>>>>>>> Wrong. Bigger apertures allow higher resolution. That's why big >>>>>>>>>> telescopes are better than tiny ones. >>>>>>>>> Telescopes are focused at infinity so that is a different case. >>>>>>>> ?!? >>>>>>>> >>>>>>>> Why is that different? >>>>>>> Because their optics are fixed >>>>>> Nope. >>>>>> >>>>>>> and you want the biggest lens/mirror >>>>>>> you can get. >>>>>> Because bigger means higher resolution. >>>>> I think it's because telescopes have very large focal lengths so the >>>>> aperture needed to avoid diffraction becomes very large. >>>> I think that you're not making sense. >>> What's wrong with the explanation? Take a 4 inch telescope (100mm >>> aperture) with a focal length of 1000mm, that's f/10, hardly a fast lens. >> >> <snip> The subject is resolution. > >You mean magnification? http://en.wikipedia.org/wiki/Angular_resolution Read. Learn. Stop asking stupid questions/ -- Ray Fischer rfischer(a)sonic.net
From: Ray Fischer on 29 May 2010 01:56
DanP <dan.petre(a)gmail.com> wrote: >On 23 May, 22:59, rfisc...(a)sonic.net (Ray Fischer) wrote: >> DanP �<dan.pe...(a)hotmail.com> wrote: >> >On 23 May, 18:50, rfisc...(a)sonic.net (Ray Fischer) wrote: >> >> DanP �<dan.pe...(a)gmail.com> wrote: >> >> >On May 23, 3:31�am, rfisc...(a)sonic.net (Ray Fischer) wrote: >> >> >> >> Wrong. �Bigger apertures allow higher resolution. �That's why big >> >> >> telescopes are better than tiny ones. >> >> >> >Telescopes are focused at infinity so that is a different case. >> >> >> ?!? >> >> >> Why is that different? >> >> >Because their optics are fixed >> >> Nope. > >You are right, land telescopes optics need focusing just like >binoculars. But I had in mind astronomical telescopes. So did I. >> >and you want the biggest lens/mirror >> >you can get. >> >> Because bigger means higher resolution. > >True only for telescopes and binoculars. Did you think that the subject under discussion was elephants? -- Ray Fischer rfischer(a)sonic.net |