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#21
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Math question - sort of
Kennedy McEwen wrote:
In article , Eric Miller writes Kennedy McEwen wrote: If it is just about the math then you need to quantify the lens quality contribution as well No, the question posed in the original post had nothing to do with that. I suggest you read what you wrote in your question again and, in future ask what you mean or mean what you ask! You specifically refer to resolution and that is a lot more than just pixel density! - your math is less than half the story, dealing only with pixel geometry. That would actually be the whole story, since the original question strictly concerned the pixels. No, you stated: "if there is a way to think of resolution as effective focal length versus the 10D". Which is a selective quote designed to explain your need to pontificate about something other than what was really asked (and as argument that the most direct and succinct response to the question posed really missed the point), which was: "So, for example, if I were to get a 7D at 18 megapixels how would that compare to 10D resolution wise in terms of what focal length lens would I have had to put on the 10D to get a 5 inch tall bird at 20 meters (or any distance) to be rendered by the same number of pixels (one dimension only or my head will hurt too much) on the 10D that it would be rendered on the 7D using the 400mm lens." It isn't surprising that, on the usenet, posters will feel the necessity to take every question as an opportunity to educate those lesser minds about what they really should have asked. But why hide from that conceit by quoting a selected part of the preamble to my math question to suggest that I really asked about that which you want to talk about? Seriously, why not just say what your thinking? You're smarter than everyone else and we should all worship you, right? Oh wait, let me mimic that little voice you just heard, "Remember, this post is an opportunity to tell them more of what we know about what they should have been asking, but were too ignorant to, hee hee hee . . . God we are smart." Eric Miller www.dyesscreek.com |
#22
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Math question - sort of
In article , Eric Miller
writes Kennedy McEwen wrote: In article , Eric Miller writes Kennedy McEwen wrote: If it is just about the math then you need to quantify the lens quality contribution as well No, the question posed in the original post had nothing to do with that. I suggest you read what you wrote in your question again and, in future ask what you mean or mean what you ask! You specifically refer to resolution and that is a lot more than just pixel density! - your math is less than half the story, dealing only with pixel geometry. That would actually be the whole story, since the original question strictly concerned the pixels. No, you stated: "if there is a way to think of resolution as effective focal length versus the 10D". Which is a selective quote designed to explain your need to pontificate about something other than what was really asked No it is an exact quote of your question, excluding the waffle that put it in context as that was already clear from the preceding thread. "So, for example, if I were to get a 7D at 18 megapixels how would that compare to 10D resolution wise in terms of what focal length lens would I have had to put on the 10D to get a 5 inch tall bird at 20 meters (or any distance) to be rendered by the same number of pixels (one dimension only or my head will hurt too much) on the 10D that it would be rendered on the 7D using the 400mm lens." Context. The answer is NOT simply scaling pixel size of the 10D to the 7D, which is what you were given. Without taking optical resolution into account the equivalent focal length you would need on the 10D compared to the 7D could be close to 50% higher than is in fact the case! Optics, even perfect optics, don't have infinite resolution! When the optical resolution is close to the pixel resolution then they MUST be taken into account to answer your question, or you end up with meaningless unresolved pixels. You seem to have a major problem understanding that. It isn't surprising that, on the usenet, posters will feel the necessity to take every question as an opportunity to educate those lesser minds about what they really should have asked. When you were 5 and asked your Mom where you came from, you were probably happy with her reply that a stork brought you. By the time you were 10 you would expect a better, more complete answer, to exactly the same question. By the time you were 15 you ought to know the full answer yourself. Stop behaving like a 5 year old - there is no Santa Claus, even if some of your friends still believe there is! Oh wait, let me mimic that little voice you just heard, "Remember, this post is an opportunity to tell them more of what we know about what they should have been asking, but were too ignorant to, hee hee hee . . . God we are smart." Smart enough to know that any question I ask may well have an answer which is more complex than I expected and with enough common decency not to criticise those who make the effort to explain that. Carry on living in ignorance: the x1.7 scale factor given by the partial answer is at least 50% too high. A 400mm lens on the 7D would NOT give equivalent resolution to a 680mm lens on a 10D: you will be lucky to achieve half of that 280mm effective focal length extension depending on the optical resolution of the 400mm lens in question. In other words 540mm, or less, equivalence in terms of what is actually RESOLVED. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#23
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Math question - sort of
John Navas wrote in
: On Fri, 25 Sep 2009 17:10:27 -0400, "Charles" wrote in : Let the reader decide: http://www.luminous-landscape.com/tu...solution.shtml Sensors for larger formats are approaching the diffraction limit of real lenses, and it is more difficult to get high levels of aberration suppression for them. The point is that you cannot fully exploit the resolution potential of high-resolution sensors with regular mass-produced lenses, particularly for larger formats. The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Lower densities lower the resolution, so you see less of everything, including subject detail. You position is all "talk" and "logic". You can not demonstrate what you believe, because it only exists in bad logic and bad paradigms. Here's what happens when you try to demonstrate, and go about it the right way: You shoot the same scene with the same lens, same ISO, same Av and Tv, and then you use a converter with no noise reduction, and upsample critical crops from both images to the same subject size. No matter how much lens fault is brought into the light with the higher density, the higher density still has a more accurate rendition of the subject, because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less agressive sampling does not avoid lens issues; it just makes it harder to tell why the image has so much less real subject detail. |
#24
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Math question - sort of
John Sheehy wrote:
John Navas wrote in : On Fri, 25 Sep 2009 17:10:27 -0400, "Charles" wrote in : Let the reader decide: http://www.luminous-landscape.com/tu...solution.shtml Sensors for larger formats are approaching the diffraction limit of real lenses, and it is more difficult to get high levels of aberration suppression for them. The point is that you cannot fully exploit the resolution potential of high-resolution sensors with regular mass-produced lenses, particularly for larger formats. The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Lower densities lower the resolution, so you see less of everything, including subject detail. You position is all "talk" and "logic". You can not demonstrate what you believe, because it only exists in bad logic and bad paradigms. Here's what happens when you try to demonstrate, and go about it the right way: You shoot the same scene with the same lens, same ISO, same Av and Tv, and then you use a converter with no noise reduction, and upsample critical crops from both images to the same subject size. No matter how much lens fault is brought into the light with the higher density, the higher density still has a more accurate rendition of the subject, because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less agressive sampling does not avoid lens issues; it just makes it harder to tell why the image has so much less real subject detail. Is that another way of saying the Kodak empirical formula for end image resolution (on film) is... 1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ? So increasing either the sensor density or the lens resolution results in higher output resolution, though of course with diminishing returns. |
#25
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Math question - sort of
John Sheehy wrote:
The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Extreme microlenses can emphasize CA and even vignetting. I don't know if that's necessarily proportional to pixel density but it appears to be more of an issue. Lower densities lower the resolution, so you see less of everything, including subject detail. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam |
#26
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Math question - sort of
Paul Furman wrote:
Eric Miller wrote: I went from the 10D to the 5D. When I had my 10D, I learned to like the 1.6x way of fooling myself into thinking my 400mm lens was a 560mm lens. Now I am thinking of getting myself another birding camera and am trying to figure out if there is a way to think of resolution as effective focal length versus the 10D. So, for example, if I were to get a 7D at 18 megapixels how would that compare to 10D resolution wise in terms of what focal length lens would I have had to put on the 10D to get a 5 inch tall bird at 20 meters (or any distance) to be rendered by the same number of pixels (one dimension only or my head will hurt too much) on the 10D that it would be rendered on the 7D using the 400mm lens. It's all relative,... ...but yes it would be useful to have a common terminology for describing pixel magnification rather than 35mm equivalent FOV. Hmm, I was thinking macro when I wrote "pixel magnification" but at infinity I guess it would be pixels/field of view in degrees? On second thought, the original question is about magnification, just magnification at/near infinity. FOV only matters here if the 5 inch tall bird goes outside the frame. Print size doesn't exactly matter either unless you want the result in inches instead of pixels, the only question is how much the bird can be enlarged. Set the number relative to a 'normal' lens, which coincidentally is very close to 50 degrees for the diagonal FOV of a 50mm lens on a 35mm camera. Then let's use 300dpi as a standard metric for enlargement, on an 8x10 print that's 2400x3000 or 7.2MP. So, a full frame 7.2MP camera making an acceptable 8x10 print with a normal lens of 50 degrees diagonal field of view represents the basepoint. This is still a handy basepoint. How many pixels tall would the 5 inch bird be for a 7.2MP full frame 35mm camera, focused to infinity? I guess we need to know how far away the bird is. Damn, now I've exceeded my mathematical skills and/or patience... ...It would look something like if you doubled the focal length, the number would be 2 and the number is 1 with the default setup. Or if you double the linear pixel count, that doubles the number also. So the pixel spacing is really all you need, though it's nice to nail it all back to that normal lens at infinity and an 8x10 print as the basepoint. A 500mm lens on FX would be a 10 and a 10mm FX fisheye would be -5. Yeah, this is magnification, like binoculars, microscopes & telescopes are described as 5x, 10x, etc. scratch this comment: I'm not certain what doubling the megapixel count would do to the number, probably not double it. Can anyone finish my logic? A chart would be nice g. Lastly, the lens has resolution limits so you can say that the lens is only good up to a particular magnification and decide not to waste money on pixels beyond that point. However, the point where a lens gives up is variable according to many factors like how close to the edge or center, what aperture, subject distance/magnification, etc. The MTF charts have to pick a narrow definition and the nyquist lines on those have to pick a simple theoretical diffraction point but there is usually some discernible detail beyond that even if it doesn't meet the strict criteria. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam |
#27
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Math question - sort of
On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne
wrote: John Sheehy wrote: John Navas wrote in : On Fri, 25 Sep 2009 17:10:27 -0400, "Charles" wrote in : Let the reader decide: http://www.luminous-landscape.com/tu...solution.shtml Sensors for larger formats are approaching the diffraction limit of real lenses, and it is more difficult to get high levels of aberration suppression for them. The point is that you cannot fully exploit the resolution potential of high-resolution sensors with regular mass-produced lenses, particularly for larger formats. The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Lower densities lower the resolution, so you see less of everything, including subject detail. You position is all "talk" and "logic". You can not demonstrate what you believe, because it only exists in bad logic and bad paradigms. Here's what happens when you try to demonstrate, and go about it the right way: You shoot the same scene with the same lens, same ISO, same Av and Tv, and then you use a converter with no noise reduction, and upsample critical crops from both images to the same subject size. No matter how much lens fault is brought into the light with the higher density, the higher density still has a more accurate rendition of the subject, because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less agressive sampling does not avoid lens issues; it just makes it harder to tell why the image has so much less real subject detail. Is that another way of saying the Kodak empirical formula for end image resolution (on film) is... 1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ? So increasing either the sensor density or the lens resolution results in higher output resolution, though of course with diminishing returns. Film has silver grain (analog photosites) sizes of 2um or less, the size of photosites on most small sensor cameras of 1/2.5 being approx. 2um. You will always be limited to your weakest link. If you increase the lens resolution you are limited to the resolution of your sensor being 4-8um in photosite sizes. (Luckily, in P&S cameras the optics quality and resolution is matched to the photosite sizes.) If you increase the pixel density without increasing the lens quality then all you are capturing with those smaller photosites are the blurry edges afforded by the lens. No gain in useful information. A bit like those toy telescopes that advertise 600x magnification on a 2" diameter objective lens. All you are doing is magnifying blur beyond 50x magnification with a 2" lens. Or those that put high-gain amplifiers on their fringe-area TV antennas to only amply noise. It's not an "either/or" venture. It's an "and" issue. |
#28
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Math question - sort of
Paul Furman wrote in
: John Sheehy wrote: The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Extreme microlenses can emphasize CA and even vignetting. I don't know if that's necessarily proportional to pixel density but it appears to be more of an issue. Lower densities lower the resolution, so you see less of everything, including subject detail. I meant the density itself. Of course, microlenses could be poorly designed. Even then, however, oversampling allows extemely easy and smooth correction of CA, both from the lens, and that generated by poor microlenses. |
#29
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Math question - sort of
You Are The Weakest Link wrote:
On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne wrote: John Sheehy wrote: John Navas wrote in : On Fri, 25 Sep 2009 17:10:27 -0400, "Charles" wrote in : Let the reader decide: http://www.luminous-landscape.com/tu...solution.shtml Sensors for larger formats are approaching the diffraction limit of real lenses, and it is more difficult to get high levels of aberration suppression for them. The point is that you cannot fully exploit the resolution potential of high-resolution sensors with regular mass-produced lenses, particularly for larger formats. The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Lower densities lower the resolution, so you see less of everything, including subject detail. You position is all "talk" and "logic". You can not demonstrate what you believe, because it only exists in bad logic and bad paradigms. Here's what happens when you try to demonstrate, and go about it the right way: You shoot the same scene with the same lens, same ISO, same Av and Tv, and then you use a converter with no noise reduction, and upsample critical crops from both images to the same subject size. No matter how much lens fault is brought into the light with the higher density, the higher density still has a more accurate rendition of the subject, because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less agressive sampling does not avoid lens issues; it just makes it harder to tell why the image has so much less real subject detail. Is that another way of saying the Kodak empirical formula for end image resolution (on film) is... 1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ? So increasing either the sensor density or the lens resolution results in higher output resolution, though of course with diminishing returns. It's not an "either/or" venture. It's an "and" issue. You really don't know how to read and understand that "increasing either" also includes "increasing both" do you? |
#30
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Math question - sort of
On Sun, 27 Sep 2009 21:02:51 -0400, Alan Browne
wrote: You Are The Weakest Link wrote: On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne wrote: John Sheehy wrote: John Navas wrote in : On Fri, 25 Sep 2009 17:10:27 -0400, "Charles" wrote in : Let the reader decide: http://www.luminous-landscape.com/tu...solution.shtml Sensors for larger formats are approaching the diffraction limit of real lenses, and it is more difficult to get high levels of aberration suppression for them. The point is that you cannot fully exploit the resolution potential of high-resolution sensors with regular mass-produced lenses, particularly for larger formats. The lenses are to blame for any optical issues with high densities. The higher density *NEVER* exacerbates any lens problems. Lower densities lower the resolution, so you see less of everything, including subject detail. You position is all "talk" and "logic". You can not demonstrate what you believe, because it only exists in bad logic and bad paradigms. Here's what happens when you try to demonstrate, and go about it the right way: You shoot the same scene with the same lens, same ISO, same Av and Tv, and then you use a converter with no noise reduction, and upsample critical crops from both images to the same subject size. No matter how much lens fault is brought into the light with the higher density, the higher density still has a more accurate rendition of the subject, because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less agressive sampling does not avoid lens issues; it just makes it harder to tell why the image has so much less real subject detail. Is that another way of saying the Kodak empirical formula for end image resolution (on film) is... 1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ? So increasing either the sensor density or the lens resolution results in higher output resolution, though of course with diminishing returns. It's not an "either/or" venture. It's an "and" issue. You really don't know how to read and understand that "increasing either" also includes "increasing both" do you? You don't know how to comprehend that increasing either does NOT include increasing both. Pray tell, if you have a sensor that can only record the absolute minimum of (for sake of argument) 3" of arc, how then will a lens that can resolve 1" of arc be recorded on that sensor? If you have a sensor that can record 1" of arc, how then can a lens that can only resolve 3" of arc record 1" of arc on that sensor? You will always be limited by your weakest resolution link. Now if you add in antialiasing masks, printer limitations, and the limits of the human eye depending on viewing distance, then the resolution limits climbs exponentially. You're an idiot pretend-photographer troll. Plain and simple. Proved 100%. You ARE the weakest link. throwing a dead goat under its troll's bridge to see if it'll go feed on that |
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