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jrista said:awinphoto said:
Snip!
A perfect (i.e. diffraction limited rather than optical aberration limited) lens at an aperture of f/1.38 would be necessary to achieve 114lp/mm with the 7D sensor. To my knowledge, such a lens does not exist (or if it did, it would have to be an extreme supertelephoto lens, where most incident light is already collimated, producing very little optical aberrations to start with.) When it comes to system resolution (or system blur), you get the most benefit by improving the lowest common denominator. In this case, the sensor is the lowest common denominator when we are using f/4. As such, we could gain more system resolution by increasing sensor resolution relative to lens resolution. If we used a sensor capable of 173lp/mm, the same as a diffraction limited lens at f/4, we would have a 40mp APS-C sensor. Our total system resolution would be about 122lp/mm at f/4. As you have probably figured, a 40mp APS-C sensor would be quite a feat to manufacture, probably have some very undesirable noise and electronic characteristics, and would likely be extremely expensive. It would also likely exhibit similar softness, as ironically, the sensor is still producing images with 40% more pixels than are necessary to produce a sharp photo.Personally, I prefer my lenses to outresolve my sensors a bit, which means the sensors never produce more pixels than necessary to create a sharp photo strait out of the camera.
This sound perfectly like the Theory of Constraints! http://en.wikipedia.org/wiki/Theory_of_constraints
I think a number of persons need to read this detail jrista has gone into.
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te4o said:jrista, FANTASTIC TEACHING! Thank you! Is this actually your profession or your hobby? I think you should post a small summary into Nikonrumors. Or it should be linked to the D800 manual
Aye, your welcome.
This is really just a hobby...I like to know how things work. I'd love to post a summary to Nikon rumors, however I'd probably get flamed into oblivion. Keep in mind, the D800 is actually a lower spatial resolution than the 7D by a fair percentage (you would need a 47mp FF sensor to have 4.3 micron pixels), and as such, its still well within the realm where it can produce very nice, sharp photos, so it really is a good camera...just keep in mind, it has about 87% the resolution of the 7D, so the 7D is pushing the limits quite a bit more than the D800 is. I wasn't trying to indicate people should not buy a D800, actually I think its an excellent camera for those who explicitly need high quality, high resolution photographs.
rpt said:
YUP! The theory of constraints applies to a lot of things. Its actually rather sad that it is referred to rather infrequently in general theory of things like Cameras.
rpt said:jrista, Thank you! you just cured my "24 megapixelitis for 7D2"!
;D Glad to be of service. To qualify that, though....if Canon could produce a 24mp APS-C sensor that had considerably less noise than the 7D, and supported an extra stop or two of high ISO...I'd buy one. The 7D is at limits as much because its pushing resolution as it is because its electronic noise is a bit too high for that resolution. Electronic noise and an aggressive low-pass filter does eat into the "fine" detail that the 7D is theoretically capable of resolving. Nothing you can do about photon noise, but improving electronic noise would make a higher resolution 7D II sensor more capable of recording that finer level of detail that a similar-megapixel FF sensor could not resolve. If a 24mp 7D II was capable of cleanly resolving super fine detail (which the current 7D is marginally able to do), then it WOULD still be worth it.
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jrista said:te4o said:jrista, FANTASTIC TEACHING! Thank you! Is this actually your profession or your hobby? I think you should post a small summary into Nikonrumors. Or it should be linked to the D800 manual
Aye, your welcome.
I'd love to post a summary to Nikon rumors, however I'd probably get flamed into oblivion. Keep in mind, the D800 is actually a lower spatial resolution than the 7D by a fair percentage (you would need a 47mp FF sensor to have 4.3 micron pixels), and as such, its still well within the realm where it can produce very nice, sharp photos, so it really is a good camera...just keep in mind, it has about 87% the resolution of the 7D, so the 7D is pushing the limits quite a bit more than the D800 is. I wasn't trying to indicate people should not buy a D800, actually I think its an excellent camera for those who explicitly need high quality, high resolution photographs.
rpt said:
YUP! The theory of constraints applies to a lot of things. Its actually rather sad that it is referred to rather infrequently in general theory of things like Cameras.
rpt said:jrista, Thank you! you just cured my "24 megapixelitis for 7D2"!
;D Glad to be of service. To qualify that, though....if Canon could produce a 24mp APS-C sensor that had considerably less noise than the 7D, and supported an extra stop or two of high ISO...I'd buy one. The 7D is at limits as much because its pushing resolution as it is because its electronic noise is a bit too high for that resolution. Electronic noise and an aggressive low-pass filter does eat into the "fine" detail that the 7D is theoretically capable of resolving. Nothing you can do about photon noise, but improving electronic noise would make a higher resolution 7D II sensor more capable of recording that finer level of detail that a similar-megapixel FF sensor could not resolve. If a 24mp 7D II was capable of cleanly resolving super fine detail (which the current 7D is marginally able to do), then it WOULD still be worth it.
I agree with the others here; It is really educational, and I really like when people are willing to get into the essence of things. That said, I realise that a lot of this is far over my head, but that does not diencourage me, rather, I realize that there are new interesting things to learn about.
You said that there is nothing one can do about photon noise, and that struck me as strange. You are probably right, but as a general rule I am sceptic to deterministic statements. If there is one thing we have learned from the history of science, - is that what at a certain point in time seemed to be impossible, are suddendly resolved. I will not quote Kuhn here, but reconfigurations of knowledge, old discarded ideas are brought to life again with the support of supplementary technology and knowledge and so forth.. Just a thought.
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Quasimodo said:
Sorry, I should have included proper context in regards to photon noise. In that, I mean with current types of sensor technology, not "period". There are actually some pretty intriguing ideas for new types of sensor design that may indeed help us resolve some of the "photon shot noise" problem. One of the ones I like most is DFS or Digital Film Sensors. The general idea is that instead of having pixels that are always relatively large, use pixels that are times smaller than we have now (sub-micron size), and when a photon strikes just one pixel, activate a "digital grain"....similar to how silver halide in film works. As more photons strike pixels in that particular grain, the grain as a whole would accumulate "charge", and therefor intensity. The genius about this approach is that it is highly flexible, and you can do some amazing things. The original article (http://ericfossum.com/Publications/Papers/Gigapixel%20Digital%20Film%20Sensor%20Proposal.pdf) did not really go into detail about how that approach might be capable of addressing various types of noise, however you could do something along the lines of arbitrary sub-"grain" splits, dividing very large "grains" into smaller "grains" as light became more evenly distributed across the sensor, allowing resolution to grow dynamically as the characteristics of incoming light permitted. You might also be able to do some hardware-level pixel (sub-"grain") level redistribution of charge to normalize photon shot noise across neighboring pixels, so long as they did not affect "grains" above a certain level of granularity (i.e. the adjustment of charge did not affect a configurable level of resolution/did not blur detail above a certain level of fineness.)
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