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From: Paul Furman on 23 May 2010 22:50 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.
From: Ray Fischer on 24 May 2010 02:11 Paul Furman <paul-@-edgehill.net> wrote: >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. You seem to be stupid. The subject is resolution. -- Ray Fischer rfischer(a)sonic.net
From: DanP on 24 May 2010 05:09 On 23 May, 22:06, "J. Clarke" <jclarke.use...(a)cox.net> wrote: > On 5/23/2010 4:03 PM, DanP 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 and you want the biggest lens/mirror > > you can get. > > > Binoculars have focus and if you want a bigger DOF you pick smaller > > lenses. The less light you let through the longer the DOF. > > > In cameras DOF is a relation of the f number which in turn depends of > > the size of the lens and the size of the internal diaphragm. > > The issue under discussion is not DOF, it's sharpness. So what > relevance do you believe DOF to have? Take an optics course sometime > and you'll be surprised at how much of what you think you know is wrong.- Hide quoted text - > > - Show quoted text - The question is are bigger size lens better for cameras? To answer that properly you need to compare 2 lenses with different lens diameters _at_the_same_aperture_ (f number). We all know faster lens are better so it is not fair to compare faster bigger lenses with smaller slower ones. That means the DOF has to be the same for both lenses and it also helps to think of it when you make the analogy between binoculars and cameras. If I am wrong just point out where, looks like you know better than me having taken that optics course. DanP
From: DanP on 24 May 2010 05:12 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. > > >and you want the biggest lens/mirror > >you can get. > > Because bigger means higher resolution. True only for telescopes and binoculars. DanP
From: Remmy Martin on 24 May 2010 05:38
On Mon, 24 May 2010 02:09:06 -0700 (PDT), DanP <dan.petre(a)gmail.com> wrote: >On 23 May, 22:06, "J. Clarke" <jclarke.use...(a)cox.net> wrote: >> On 5/23/2010 4:03 PM, DanP 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 and you want the biggest lens/mirror >> > you can get. >> >> > Binoculars have focus and if you want a bigger DOF you pick smaller >> > lenses. The less light you let through the longer the DOF. >> >> > In cameras DOF is a relation of the f number which in turn depends of >> > the size of the lens and the size of the internal diaphragm. >> >> The issue under discussion is not DOF, it's sharpness. �So what >> relevance do you believe DOF to have? �Take an optics course sometime >> and you'll be surprised at how much of what you think you know is wrong.- Hide quoted text - >> >> - Show quoted text - > >The question is are bigger size lens better for cameras? > >To answer that properly you need to compare 2 lenses with different >lens diameters _at_the_same_aperture_ (f number). > >We all know faster lens are better so it is not fair to compare faster >bigger lenses with smaller slower ones. > Wrong. >That means the DOF has to be the same for both lenses and it also >helps to think of it when you make the analogy between binoculars and >cameras. > Wrong. >If I am wrong just point out where, looks like you know better than me >having taken that optics course. > How much money do you have? Educating you would cost lots of your money. And lots of wasted time on anyone's part. |