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From: DanP on 24 May 2010 07:38 On 24 May, 10:38, Remmy Martin <remmymar...(a)gooddrinksnotspam.net> wrote: > On Mon, 24 May 2010 02:09:06 -0700 (PDT), DanP <dan.pe...(a)gmail.com> wrote: > >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.- Hide quoted text - > When did I express my intention to go on a optics course? You got the wrong idea as usual. DanP
From: Remmy Martin on 24 May 2010 07:43 On Mon, 24 May 2010 04:38:59 -0700 (PDT), DanP <dan.petre(a)gmail.com> wrote: >On 24 May, 10:38, Remmy Martin <remmymar...(a)gooddrinksnotspam.net> >wrote: >> On Mon, 24 May 2010 02:09:06 -0700 (PDT), DanP <dan.pe...(a)gmail.com> wrote: > >> >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.- Hide quoted text - >> > >When did I express my intention to go on a optics course? >You got the wrong idea as usual. > > >DanP The only "wrong idea" here is any that you seem to type. You might have better success trolling newsgroups where you are not so easily outted for your ignorance and stupidity.
From: Paul Furman on 24 May 2010 11:47 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? I'm talking about resolution. The telescope example can't get much slower or diffraction will waste pixels. An f/10 telescope doesn't provide more detail across 12MP of sensor than a 50mm lens at f/10. Maybe you are thinking about magnification rather than resolution. You need a larger telescope to get more magnification but it doesn't help to have a telescope (or camera lens) faster than the diffraction/pixel size/nyquist/whatever you want to call it. For normal camera lenses, faster doesn't help unless you need shorter exposures in low light, or want to isolate the subject for creative reasons. It won't buy you resolution. When you get to macro, magnification again rears it's head against the aperture and diffraction limits resolution, necessitating larger apertures.
From: Paul Furman on 24 May 2010 11:51 DanP 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? Not necessarily. > 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. > We all know faster lens are better so it is not fair to compare faster > bigger lenses with smaller slower ones. Utter confusion. You're going in circles now. > 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 12:36
On 24 May, 16:51, Paul Furman <pa...@-edgehill.net> 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 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. DanP |