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#41
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Stacked teleconverters (was Telephoto Reach and Digital Cameras- lens comparison)
me wrote:
On Fri, 17 Dec 2010 07:43:54 -0700, "Roger N. Clark (change username to wrote: I have not seen any zoom ;ens that will work well with stacked TCs, because zoom lenses are not that sharp. Only because Canon doesn't make anything in the class of the Nokon 200-400mm f/4 VR Ior II. You are right. Canon does not make anything in the class of the 200-400 VR (I wish they did). But as good as that lens is, it is still not nearly as sharp as the fixed focal length super telephotos. It would show a lot of softness with stacked TCs. Roger |
#42
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Telephoto Reach and Digital Cameras - lens comparison
Dialogue of Roger and SZ condensed to:
You are not getting it. Simple physics proves you are wrong. Regarding image detail, the super zoom P&S cameras have clear apertures on the order of an inch or less. Diffraction from such a small lens means poor subject resolution. A DSLR with even a lower end fixed telephoto like 300 f/4 has about a 3-inch clear aperture, thus on the order of 3x higher resolution on a subject. The 3x larger diameter lens delivers 9x more light. More light = finer gradations due to better signal-to-noise ratio. Again, this is simple physics. There is no contest between a DSLR versus P&S whether telephoto resolution on a subject or color tonality, or signal-to-noise ratio. Simple physics, the DSLR wins. You are wrong. It has to do with both lens physics and sensor physics. Consider two cameras, one with double the sensor size, double the lens focal length, and double the pixel size, and the same f/ratio lens. The lens has 4 times the area so collects 4 times the light. The sensors have the same spatial resolution, but the larger pixels collect 4 times the light from the lens delivering 4 times the light. The signal-to-noise ratio is double on the large sensor camera. The higher signal-to-noise ratio delivers finer tonality and greater dynamic range. This is well proven and simple physics. As for your physics proving everything, it FAILS because it does NOT take into account the figure of the lenses. The lenses on the superzoom camera can and ARE polished to diffraction-limited quality. They have to be in order to allow the photosites resolve individual details. Otherwise nobody would buy them. Thereby allowing them to have more resolution at larger apertures. DSLR glass is NEVER ground to diffraction-limited quality, because the cost to do so puts them outside the reach of every consumer, therefore they can never attain diffraction-limited resolutions at ANY useful aperture. What a laugh! Physics does very well. Again it is simple physics that shows that the big lenses with DSLRs doesn't even need to be close to diffraction limited in other to deliver better resolution on a subject compared to the tiny lenses on P&S super zoom cameras. Simple physics proves it. Simple equation: Dawes limit = 5.45/D where D=lens clear aperture diameter. You can try shoving the physics wherever you want to but it won't change the basic and well understood laws of physics. I think the problem here is that SZ thinks "diffraction limited" somehow translates to "diffraction eliminated," and ( in his / her mind) that ultimately means "better." Just because a fine polish can reduce the amount of diffraction on a small lens element, it does not follow that there miraculously is no dispersion ((or even) less dispersion) of light across the resulting smaller focal plane by utilizing those tiny elements in a minimalistic design. The resultant camera is smaller and cheaper to build, and yields satisfactory results for many situations, but it is still physically impossible for it to exceed the images produced by DSLR's. I find this discussion rather interesting, since those in the superzoom camp don't seem to realize that the whole idea of eliminating diffraction is more than a bit counter productive, in that diffraction is a key factor in what the human eye actually perceives. I mean, what we normally see is an image that stems from solar light as defused through the atmosphere and diffracted through the lens of the human eye. Accordingly, there is no " perfectly clear" image prototype we can use as a standard. From an artistic perspective, diffraction is good. Think about it. We take a prism, shine a light through it and, voila, a rainbow of colour appears! Translate that to the curved surface of a lens and it doesn't take much imagination to understand how a bit of diffraction can dramatically spruce up the colours in an ordinary scene. On the other hand, from a more clinical point of view, if all one is interested in is detail, one might prefer a more sterile capture if all one is after is the systematic verification of a physical phenomena. It is the natural defusion and diffraction of light our mind decodes in order to render the rich tapestries we conceive to physically be situated there in front of us. We like variation. As such, if we actually could remove diffraction and defusion from human sight, effectively reducing what we see down to the finite number of colours and shades physically constituting the objects we capture in our viewfinders, I'm sure we'd be rather bored with the bland results. Take Care, Dudley |
#43
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Telephoto Reach and Digital Cameras - lens comparison
Dudley Hanks wrote:
Dialogue of Roger and SZ condensed to: You are not getting it. Simple physics proves you are wrong. Regarding image detail, the super zoom P&S cameras have clear apertures on the order of an inch or less. Diffraction from such a small lens means poor subject resolution. A DSLR with even a lower end fixed telephoto like 300 f/4 has about a 3-inch clear aperture, thus on the order of 3x higher resolution on a subject. The 3x larger diameter lens delivers 9x more light. More light = finer gradations due to better signal-to-noise ratio. Again, this is simple physics. There is no contest between a DSLR versus P&S whether telephoto resolution on a subject or color tonality, or signal-to-noise ratio. Simple physics, the DSLR wins. You are wrong. It has to do with both lens physics and sensor physics. Consider two cameras, one with double the sensor size, double the lens focal length, and double the pixel size, and the same f/ratio lens. The lens has 4 times the area so collects 4 times the light. The sensors have the same spatial resolution, but the larger pixels collect 4 times the light from the lens delivering 4 times the light. The signal-to-noise ratio is double on the large sensor camera. The higher signal-to-noise ratio delivers finer tonality and greater dynamic range. This is well proven and simple physics. As for your physics proving everything, it FAILS because it does NOT take into account the figure of the lenses. The lenses on the superzoom camera can and ARE polished to diffraction-limited quality. They have to be in order to allow the photosites resolve individual details. Otherwise nobody would buy them. Thereby allowing them to have more resolution at larger apertures. DSLR glass is NEVER ground to diffraction-limited quality, because the cost to do so puts them outside the reach of every consumer, therefore they can never attain diffraction-limited resolutions at ANY useful aperture. What a laugh! Physics does very well. Again it is simple physics that shows that the big lenses with DSLRs doesn't even need to be close to diffraction limited in other to deliver better resolution on a subject compared to the tiny lenses on P&S super zoom cameras. Simple physics proves it. Simple equation: Dawes limit = 5.45/D where D=lens clear aperture diameter. You can try shoving the physics wherever you want to but it won't change the basic and well understood laws of physics. I think the problem here is that SZ thinks "diffraction limited" somehow translates to "diffraction eliminated," and ( in his / her mind) that ultimately means "better." Just because a fine polish can reduce the amount of diffraction on a small lens element, it does not follow that there miraculously is no dispersion ((or even) less dispersion) of light across the resulting smaller focal plane by utilizing those tiny elements in a minimalistic design. The resultant camera is smaller and cheaper to build, and yields satisfactory results for many situations, but it is still physically impossible for it to exceed the images produced by DSLR's. I find this discussion rather interesting, since those in the superzoom camp don't seem to realize that the whole idea of eliminating diffraction is more than a bit counter productive, in that diffraction is a key factor in what the human eye actually perceives. I mean, what we normally see is an image that stems from solar light as defused through the atmosphere and diffracted through the lens of the human eye. Accordingly, there is no " perfectly clear" image prototype we can use as a standard. From an artistic perspective, diffraction is good. Think about it. We take a prism, shine a light through it and, voila, a rainbow of colour appears! Translate that to the curved surface of a lens and it doesn't take much imagination to understand how a bit of diffraction can dramatically spruce up the colours in an ordinary scene. On the other hand, from a more clinical point of view, if all one is interested in is detail, one might prefer a more sterile capture if all one is after is the systematic verification of a physical phenomena. It is the natural defusion and diffraction of light our mind decodes in order to render the rich tapestries we conceive to physically be situated there in front of us. We like variation. As such, if we actually could remove diffraction and defusion from human sight, effectively reducing what we see down to the finite number of colours and shades physically constituting the objects we capture in our viewfinders, I'm sure we'd be rather bored with the bland results. Take Care, Dudley Oh, yeah, I forgot to add: "Beauty is in the mind of the Beholder, not the eye." Take Care, Dudley |
#44
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Telephoto Reach and Digital Cameras - lens comparison
Dudley Hanks wrote:
Dudley Hanks wrote: Dialogue of Roger and SZ condensed to: You are not getting it. Simple physics proves you are wrong. Regarding image detail, the super zoom P&S cameras have clear apertures on the order of an inch or less. Diffraction from such a small lens means poor subject resolution. A DSLR with even a lower end fixed telephoto like 300 f/4 has about a 3-inch clear aperture, thus on the order of 3x higher resolution on a subject. The 3x larger diameter lens delivers 9x more light. More light = finer gradations due to better signal-to-noise ratio. Again, this is simple physics. There is no contest between a DSLR versus P&S whether telephoto resolution on a subject or color tonality, or signal-to-noise ratio. Simple physics, the DSLR wins. You are wrong. It has to do with both lens physics and sensor physics. Consider two cameras, one with double the sensor size, double the lens focal length, and double the pixel size, and the same f/ratio lens. The lens has 4 times the area so collects 4 times the light. The sensors have the same spatial resolution, but the larger pixels collect 4 times the light from the lens delivering 4 times the light. The signal-to-noise ratio is double on the large sensor camera. The higher signal-to-noise ratio delivers finer tonality and greater dynamic range. This is well proven and simple physics. As for your physics proving everything, it FAILS because it does NOT take into account the figure of the lenses. The lenses on the superzoom camera can and ARE polished to diffraction-limited quality. They have to be in order to allow the photosites resolve individual details. Otherwise nobody would buy them. Thereby allowing them to have more resolution at larger apertures. DSLR glass is NEVER ground to diffraction-limited quality, because the cost to do so puts them outside the reach of every consumer, therefore they can never attain diffraction-limited resolutions at ANY useful aperture. What a laugh! Physics does very well. Again it is simple physics that shows that the big lenses with DSLRs doesn't even need to be close to diffraction limited in other to deliver better resolution on a subject compared to the tiny lenses on P&S super zoom cameras. Simple physics proves it. Simple equation: Dawes limit = 5.45/D where D=lens clear aperture diameter. You can try shoving the physics wherever you want to but it won't change the basic and well understood laws of physics. I think the problem here is that SZ thinks "diffraction limited" somehow translates to "diffraction eliminated," and ( in his / her mind) that ultimately means "better." Just because a fine polish can reduce the amount of diffraction on a small lens element, it does not follow that there miraculously is no dispersion ((or even) less dispersion) of light across the resulting smaller focal plane by utilizing those tiny elements in a minimalistic design. The resultant camera is smaller and cheaper to build, and yields satisfactory results for many situations, but it is still physically impossible for it to exceed the images produced by DSLR's. I find this discussion rather interesting, since those in the superzoom camp don't seem to realize that the whole idea of eliminating diffraction is more than a bit counter productive, in that diffraction is a key factor in what the human eye actually perceives. I mean, what we normally see is an image that stems from solar light as defused through the atmosphere and diffracted through the lens of the human eye. Accordingly, there is no " perfectly clear" image prototype we can use as a standard. From an artistic perspective, diffraction is good. Think about it. We take a prism, shine a light through it and, voila, a rainbow of colour appears! Translate that to the curved surface of a lens and it doesn't take much imagination to understand how a bit of diffraction can dramatically spruce up the colours in an ordinary scene. On the other hand, from a more clinical point of view, if all one is interested in is detail, one might prefer a more sterile capture if all one is after is the systematic verification of a physical phenomena. It is the natural defusion and diffraction of light our mind decodes in order to render the rich tapestries we conceive to physically be situated there in front of us. We like variation. As such, if we actually could remove diffraction and defusion from human sight, effectively reducing what we see down to the finite number of colours and shades physically constituting the objects we capture in our viewfinders, I'm sure we'd be rather bored with the bland results. Take Care, Dudley Oh, yeah, I forgot to add: "Beauty is in the mind of the Beholder, not the eye." Take Care, Dudley Before all you purists post your kindly admonishments that I am confusing diffraction and refraction, let me just poinht out that the two concepts are, shall we say, at worst rather inter-related... If the resolving power of a circular lens were only impacted by the "diffraction" effect of waves passing around / by obstacles, how would polishing it to a micro level make any difference? I view refraction as, more or less, an extension / subset of diffraction; I'm not sure how well that goes over with the more academic scientific community. Take Care, Dudley |
#45
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Telephoto Reach and Digital Cameras - lens comparison
On Fri, 17 Dec 2010 01:06:43 -0800, bobwilliams wrote:
I admire Roger's contributions to this newsgroup and take all his data, images and conclusions very seriously. Bob Then you are a fool. He poses BAD SCIENCE as a way to get controversy so people visit his website where he then tries to sell his ****-poor tourists crapshots. He's that desperate for anyone to see his photography because nobody wants to. It's his only motive and method. His calculations have been proved wrong so many times in the past that people just stopped bothering to correct all his errors. Then idiots like you fall for his bull**** song and dance. |
#46
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Telephoto Reach and Digital Cameras - lens comparison
Superzooms Still Win wrote:
On Fri, 17 Dec 2010 01:06:43 -0800, bobwilliams wrote: I admire Roger's contributions to this newsgroup and take all his data, images and conclusions very seriously. Bob Then you are a fool. He poses BAD SCIENCE as a way to get controversy so people visit his website where he then tries to sell his ****-poor tourists crapshots. He's that desperate for anyone to see his photography because nobody wants to. It's his only motive and method. His calculations have been proved wrong so many times in the past that people just stopped bothering to correct all his errors. Then idiots like you fall for his bull**** song and dance. Bob, you should listen to SZ. He's an expert on giving bad advice and being proven wrong.. Take Care, Dudley |
#47
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Stacked teleconverters (was Telephoto Reach and DigitalCameras - lens comparison)
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#48
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Stacked teleconverters (was Telephoto Reach and Digital Cameras- lens comparison)
On 12/17/2010 4:26 PM, Roger N. Clark (change username to rnclark) wrote:
me wrote: On Fri, 17 Dec 2010 07:43:54 -0700, "Roger N. Clark (change username to wrote: I have not seen any zoom ;ens that will work well with stacked TCs, because zoom lenses are not that sharp. Only because Canon doesn't make anything in the class of the Nokon 200-400mm f/4 VR Ior II. You are right. Canon does not make anything in the class of the 200-400 VR (I wish they did). But as good as that lens is, it is still not nearly as sharp as the fixed focal length super telephotos. It would show a lot of softness with stacked TCs. Which may be why I have the issue. Have you tried stacking with a 500 mirror? -- Peter |
#49
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Telephoto Reach and Digital Cameras - lens comparison
Dudley Hanks wrote:
Before all you purists post your kindly admonishments that I am confusing diffraction and refraction, let me just poinht out that the two concepts are, shall we say, at worst rather inter-related... Dudley, They are related in that both processes change the direction that light travels. If the resolving power of a circular lens were only impacted by the "diffraction" effect of waves passing around / by obstacles, how would polishing it to a micro level make any difference? I view refraction as, more or less, an extension / subset of diffraction; I'm not sure how well that goes over with the more academic scientific community. It really is two different processes, and they generally work in the opposite direction with glass lenses over the visible spectrum. Shorter wavelengths are bent more as the light passes through a glass lens. Diffraction affects longer wavelengths more (red light). But the role of polishing has little to do with diffraction performance of a lens over the visible spectrum. Good polishing generally reduces flare, but doesn't make the lens diffraction limited. The figure of the polished lens has more to do with that, along with a multi-element design to reduce chromatic and other aberrations. So we all know who is wrong again. Roger. |
#50
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Telephoto Reach and Digital Cameras - lens comparison
Superzooms Still Win wrote:
On Fri, 17 Dec 2010 01:06:43 -0800, wrote: I admire Roger's contributions to this newsgroup and take all his data, images and conclusions very seriously. Bob Then you are a fool. He poses BAD SCIENCE as a way to get controversy so people visit his website where he then tries to sell his ****-poor tourists crapshots. He's that desperate for anyone to see his photography because nobody wants to. It's his only motive and method. His calculations have been proved wrong so many times in the past that people just stopped bothering to correct all his errors. Then idiots like you fall for his bull**** song and dance. Hmmm.. Let's look at the evidence. Throughout this thread you have been proven wrong time and time again with simple physics. When proven wrong you start lies. You can not prove specific things that are in error in anything I have said in this thread, nor on my web site. That is because the physics is correct. So then you resort to name calling, libel, and lies. Pathetic. Again, simple physics proves you wrong. So whenever you continue posting lies to this newsgroup, everyone can respond "simple physics proves you wrong." Roger |
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