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From: Paul Furman on 16 May 2010 12:50 Robert Spanjaard wrote: > Paul Furman wrote: > >>> I guess that's why this image of a peacock's feathers taken at f/4.5 >>> with an average P&S camera >> >> 2 micron pixels? > > Possibly. At that size, you'd get about 7 million pixels on a 1/2.3" > sensor. Given the full frame, it scales up to about 5 MP, if that's a panny FZ20, then 1/2.5" sensor and just a bit more than 2 microns. If it's a Canon S90, 10mp with 2 micron pixels, then it's down-sized 70%. > But while the detail may be there, you can't see it because of all the > sharpening halos. Any way you count it, the smallest possible spot at f/5.6 is about 6 microns, triple the width of the 2 micron pixels being discussed, plus softening from the antialiasing filter, so yeah, there's definitely some sharpening involved if this is genuine. However, yeah, I have heard that if you want to get the most out of a lens, 3 pixels (or more) per smidgen of detail is worth doing. But squeezing every last bit of detail out of the working aperture isn't necessarily the same as maximizing the sensor's resolution. For a full frame 35mm 12mp sensor with 8 micron pixels at 3 pixels per smidgen, the comparable aperture would be about f/20, and while that's reasonable for extracting the most info from a microscope or telescope at it's extreme limits, that's not the sharpest pixel level detail the sensor can provide. That would be more like f/8 or f/11 (this is not theoretical). And the 2 micron pixel camera is going to provide the sharpest pixel level detail at around f/2.
From: Paul Furman on 16 May 2010 14:03 DanP wrote: > Chris Malcolm wrote: >> DanP wrote: >>> DanP wrote: >>>> Bruce wrote: >>>>> DanP wrote: >>>>> >>>>>> I am still scratching my head and thinking smaller lens diameter means >>>>>> less light captured. >>>>>> So the FF sensor has to struggle and compensate for the small lens. >>>>> >>>>> The trouble is, your mindset is based around retrofocus lens designs >>>>> that need to clear the reflex mirror in a DSLR. >>>> >>>> No, I do not think of camera design at all. >>>> Instead I think of binoculars and telescopes where the bigger lens >>>> diameter gives a better IQ. >>> >>> To close the subject, after some reading and thinking lens diameter >>> does not affect the amount of light captured. >> >> Obviously not enough reading and thinking. Binoculars in effect use >> the human iris for aperture control, and use front lens diameter to >> increase the size of the exit pupil. > > I do not understand where you disagree with me. > > Is it that larger lens diameter is better for binoculars? > Or larger front lenses for cameras do not matter (but they allow a > lower f number)? > > I think I was not clear in my previous post, I was referring to camera > lenses. Larger diameter binoculars would mostly be brighter, and shallower DOF if that matters, but the resolution needs are not great for an eye compared to a 12mp sensor. Bigger does not necessarily mean better. There is some basis in what the troll says about smaller lenses being easier to manufacture to tight tolerance, but that's not the only factor. Noise is an issue in available light since you have to enlarge the small sensor image more. The smaller sensor simply gathers fewer photons, there's no way around that. Also aperture; every shot on a 2 micron pixels sensor is going to be suffering some diffraction loss unless you use an f/1.4 lens, which doesn't exist AFAIK. Every shot on a DSLR wider than f/8 is probably going to suffer some from aberrations & imperfections too. There is no free lunch in optics, there's always trade-offs. It's possible to get DSLR lenses that are sharp wide open at f/2.8 but expensive. Those will capture more photons in lower light with cleaner images and the chance to blur the background for selective focus. If you don't want all that, use the P&S. http://www2.mrc-lmb.cam.ac.uk/va/newgiantlens/tinylenses1.html ....an interesting page about the idea of small lenses generally being better (in the specific case of microscopy) and a new large lens design that was required for shallow DOF. It gives an effective aperture of f/0.85 compared to an ordinary 4x NA 2.0 objective with effective aperture at f/2.4. For comparison, a macro lens designed for 35mm like the Canon 65mm f/2.8 MP-E gives an effective aperture of f/34 at 5x with it's sharpest setting at f/5.6. Now, take the ordinary 4x .20 microscope objective at effective f/2.4. That's a lot more detail than an 8 micron pixel can capture (plus it won't fill a 35mm sensor) so theoretically you'd get the most from it using something like 1.5 micron pixels, but they chose a 35mm sensor for the f/0.85 monster lens! -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam
From: Chris Malcolm on 17 May 2010 04:42 In rec.photo.digital Bruce <docnews2011(a)gmail.com> wrote: > On Sun, 16 May 2010 10:54:43 +0100, "David J Taylor" > <david-taylor(a)blueyonder.co.uk.invalid> wrote: >>"Chris Malcolm" <cam(a)holyrood.ed.ac.uk> wrote in message >>news:859rs0F97cU1(a)mid.individual.net... >>> In rec.photo.digital Bruce <docnews2011(a)gmail.com> wrote: >>[] >>>> Exactly. There is a reason why most lenses used for portraiture are >>>> within a very short range of focal lengths. Anything significantly >>>> longer or shorter gives a rendition that most people consider is >>>> neither natural nor pleasant. >>> >>> Short focal lengths exaggerate nearer features, but I can't see the >>> problem with long focal lengths. >>[] >>> Chris Malcolm >> >>Maybe you need a little "exaggeration" to make the face "look" natural - >>as if you were taling to a person. Unless you spend your life only >>looking at faces through binoculars, that is! > Why am I not in the least surprised that Chris Malcolm "can't see the > problem with long focal lengths"? Why am I not surprised that instead of explaining what the problem is, Bruce prefers to sneer at the person who explained why he thought there wasn't a problem? -- Chris Malcolm
From: Chris Malcolm on 17 May 2010 05:13 In rec.photo.digital DanP <dan.petre(a)hotmail.com> wrote: > On 16 May, 10:49, Chris Malcolm <c...(a)holyrood.ed.ac.uk> wrote: >> In rec.photo.digital DanP <dan.pe...(a)hotmail.com> wrote: >> > On 15 May, 14:59, DanP <dan.pe...(a)hotmail.com> wrote: >> >> On 15 May, 12:41, Bruce <docnews2...(a)gmail.com> wrote: >> >> >> > On Fri, 14 May 2010 14:16:34 -0700 (PDT), DanP <dan.pe...(a)hotmail.com> >> >> > wrote: >> >> >> > >I am still scratching my head and thinking smaller lens diameter means >> >> > >less light captured. >> >> > >So the FF sensor has to struggle and compensate for the small lens. >> >> >> > The trouble is, your mindset is based around retrofocus lens designs >> >> > that need to clear the reflex mirror in a DSLR. >> >> >> No, I do not think of camera design at all. >> >> Instead I think of binoculars and telescopes where the bigger lens >> >> diameter gives a better IQ. >> > To close the subject, after some reading and thinking lens diameter >> > does not affect the amount of light captured. >> >> Obviously not enough reading and thinking. Binoculars in effect use >> the human iris for aperture control, and use front lens diameter to >> increase the size of the exit pupil. > I do not understand where you disagree with me. > Is it that larger lens diameter is better for binoculars? > Or larger front lenses for cameras do not matter (but they allow a > lower f number)? > I think I was not clear in my previous post, I was referring to camera > lenses. Your posts have not been clear. In an earlier post you said, supporting the idea with a sketch, that if focal length and sensor size stayed the same, that larger diameter lenses collected more light. This is trivially true. It's the reason why camera lenses have an aperture which is closed down to reduce the light falling on the sensor. You seemed later, after bringing binoculars into the discussion, to have decided after more "reading and thinking" that lens diameter does not affect the amount of light captured. Since this is not true for camera lenses, which you seemed earlier to understand, I assumed you must be talking about binocular lenses. Now I have no idea what you're talking about. -- Chris Malcolm
From: DanP on 17 May 2010 12:59
On May 17, 10:13 am, Chris Malcolm <c...(a)holyrood.ed.ac.uk> wrote: > Your posts have not been clear. In an earlier post you said, > supporting the idea with a sketch, that if focal length and sensor > size stayed the same, that larger diameter lenses collected more > light. This is trivially true. It's the reason why camera lenses have > an aperture which is closed down to reduce the light falling on the > sensor. > > You seemed later, after bringing binoculars into the discussion, to > have decided after more "reading and thinking" that lens diameter does > not affect the amount of light captured. Since this is not true for > camera lenses, which you seemed earlier to understand, I assumed you > must be talking about binocular lenses. > > Now I have no idea what you're talking about. > I know that bigger lens on binoculars have better IQ (more light). So I thought that bigger lenses on cameras will be better. Later I have understood that bigger lenses on cameras only permit a lower f number and nothing else. DanP |