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Author Topic: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?  (Read 12754 times)

ions

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #30 on: February 10, 2012, 08:45:03 AM »
Here is a shot using an old Nikkor 24 f/2 Ai-S lens on my 7D. I think this lens is from the 70's-80's? Her eye and some hair are pretty sharp considering there was no focus confirmation, lens is manual and the DOF was super shallow (I was sitting really close to her @f2.8.). Oh and she doesn't stop moving! ;)

This image is also saved down pretty low res for web. And the lens is totally beaten up with tons of scratches over the front element...


Great pics pdirestajr, you should share them in the Canon Body Nikon Glass thread! :)
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #30 on: February 10, 2012, 08:45:03 AM »

neuroanatomist

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #31 on: February 10, 2012, 10:07:36 AM »
And yet, my 5D2(s), can out resolve my 100mm f2.8 Macro (the non L version).
I know this because i've taken duplicate shots with same lens on 30D, 40D and 5D2 (both of them).

I'd like to see the shots and/or learn more about the method you used to make this comparison and conclude that the 5DII is outresolving the 100mm f/2.8 Macro.  I trust that you realize the pixel density of the 5DII and 30D are the same, and that the pixel density of the 40D is actually higher than the 5DII.
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pdirestajr

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #32 on: February 10, 2012, 10:30:33 AM »
Here is a shot using an old Nikkor 24 f/2 Ai-S lens on my 7D. I think this lens is from the 70's-80's? Her eye and some hair are pretty sharp considering there was no focus confirmation, lens is manual and the DOF was super shallow (I was sitting really close to her @f2.8.). Oh and she doesn't stop moving! ;)

This image is also saved down pretty low res for web. And the lens is totally beaten up with tons of scratches over the front element...


Great pics pdirestajr, you should share them in the Canon Body Nikon Glass thread! :)


Thanks! I will :)
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torger

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #33 on: February 10, 2012, 10:44:33 AM »
"outresolving the lens" is rather subjective thing.

Even if image degradation is evident due to limitations in resolving power, one will get still a little more resolution out of the system if sensor pixel count is increased further.

So it's all about when we reach the point when adding more pixels gives diminishing returns, and that is subjective indeed.

One extreme is that if we see evidence of resolution loss in corners of the cheapest lenses wide-open then we have reached that point, the other extreme is only to look at the sharpest lenses at ideal apertures in the center and accept rather soft pixels there.

In any way you see it, it is subjective. I think the point-of-diminishing returns is around 55-60 megapixels, a guess based on what I see on the 7D and dropoff on the 5D.

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #34 on: February 10, 2012, 11:34:13 AM »
When digital came out the purists cried that it would never match 35mm film, but here we are —at the opposite end of the problem.
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #35 on: February 10, 2012, 11:51:19 AM »
When digital came out the purists cried that it would never match 35mm film, but here we are —at the opposite end of the problem.

You know, this is odd... When people used film, it had an impressive tonal range, but in actuality, you only had so many ways to display your pictures... either on slides (on a wall with people at an appreciable distance away) or on print... but paper did not have the DR latitude of the film, and even at that, on negatives, the grain was always at a point where you had a catch 22 where you typically printed the 35mm film at 8x10 or smaller.  On occasion you printed an 11x14 or larger but that was pushing the limits and you expected some image degradation of some sort and some pros would counter that by putting those pics on canvas or such.  In the digital age, the best film was rated as roughly 24MP, but with printers, there's no appreciable difference between a DPI of 300 and 800 unless you really use a microscope and that is questionable at that... so now you have the 21MP 5d2, which is pretty darn close to the top film resolutions and since it cannot get any more appreciable resolution and we're stuck at 300 DPI, you now get a native 13x19 and can interpolate it even bigger... On one hand I think what much more do you really want/need/expect out of a 35mm source, a source which on film maxed out at 8x10's, but then again if it can pump more out with minimal loss of IQ, then... 
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #36 on: February 10, 2012, 12:50:32 PM »
Exactly. I think checking lens MTF charts shall be a good hint. The lower the curves off-centre the likely to fail at the edges at very high Mps (FF sensor). There is a built-in correction for light fall-off in the EOS line but resolution is a different animal. I trust the forum's reassurance though.

This seems like a larger problem that people are making out to me considering a large part of the market for 36 megapixel is going to be landscape and other uses where edge to egde sharpness is desired. Alot of the non specialised lenses people use for landscape like the 17-40 and 24-105 already have problems with boarder sharpness at 21 MP.

I wonder if this is the main reason for the new 24mm and 28mm 2.8 IS's? perhaps Canon are antcipating that there current wide zooms are going to be found wanting for landscape shooting on a high megapixel camera so have designed these primes to allow those on a budget to fully exploit such a camera? would seem to explain why the appatures are relatively modest and why they have IS, the MTF's seem to suggest both will have strong boarder performance stopped down.

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #36 on: February 10, 2012, 12:50:32 PM »

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #37 on: February 10, 2012, 05:51:03 PM »
The way I see it IS on wide angle lenses has marketing value only for the video mode. Say, in the new 24/2.8 IS hand-held camera shake occurs under 1/24sec. Four-stop IS gives you the opportunity to shoot what, 1/2sec or slightly lower? Such slow speeds are deliberately used for streaming lights, or water flow, you don't use a stabilizer for that. Sure I guess there might be a chance to take advantage of IS in a narrow apperture situation (say, f/11-16), nobody sees this as an issue. On the other hand on video means you move (pan), you may need the IS continuously working. So, Canon just combines the two worlds still and video. It makes sense all EF series to be equipped with IS now that it's affordable. For still photography shooters it's just adapting to demands of a broader, different target group.
« Last Edit: February 10, 2012, 06:10:42 PM by GND »

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #38 on: February 10, 2012, 06:00:14 PM »
To sum it up - let's first get the 40+MP DSLR (if at all) and we'll start worrying only AFTER that. Will be an interesting testing season. I am curious what the field test and real life tests of the D800 will tell us about the practicability of a high-resolution body. 
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #39 on: February 10, 2012, 07:19:04 PM »
The way I see it IS on wide angle lenses has marketing value only for the video mode. Say, in the new 24/2.8 IS hand-held camera shake occurs under 1/24sec. Four-stop IS gives you the opportunity to shoot what, 1/2sec or slightly lower? Such slow speeds are deliberately used for streaming lights, or water flow, you don't use a stabilizer for that. Sure I guess there might be a chance to take advantage of IS in a narrow apperture situation (say, f/11-16), nobody sees this as an issue. On the other hand on video means you move (pan), you may need the IS continuously working. So, Canon just combines the two worlds still and video. It makes sense all EF series to be equipped with IS now that it's affordable. For still photography shooters it's just adapting to demands of a broader, different target group.

Umm...you can't do video at 1/2sec shutter speed. That'd give you 2 frames per second. But, what IS can do, is reduce hand-held shake at 1/25sec or 1/30sec with 4 stop to make it look more like something more like the frame rate is 1/100sec or faster. Less wobble in the video without a tripod.

Also, as you said, panning can be improved, especially with the newer cameras that reduce/remove the hated moire effect and jello effect during panning.
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #40 on: February 14, 2012, 02:20:52 AM »
Well, yes, a 45MP full frame sensor does have the same pixel size as an 18MP APS-C. But it is actually really hard to out resolve that 7D sensor. Of course, pictures may look really sharp at 100%, but that doesn't mean the sensor got pushed to the limit. I use a 7D, mostly with a Canon 50/f1.4 in the studio, this means optimal lighting conditions. It does a good job at its sweet spot, thats somewhere between f4 and f8, but it gets really soft at 1.8 to hardly usable (for studio pictures) at 1.4. I can reduce a picture taken at 1.8 to 8MP and upscale it again to 18MP, without any loss of detail. And that is for the very center of the frame, the borders are considerably worse. Also note, that the 50/1.2L does not exceed the 1.4 in resolution.

I'm wondering though, how the line widths/ picture height (LW/PH) figures from lense tests translate to sensor resolution.
So 18MP result in 3456 "lines per picture height", while the highest LW/PH scores for APS-C I found were around 2600. If this was a 1:1 conversion, no APS-C sensor above 12MP would be of much use. So I'm guessing that's probably not it. I'd like to find a way to calculate the corresponding sensor resolution to any given lens resolution (and vice versa) OR know why this is not possible. Can anyone help?

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #41 on: February 14, 2012, 03:53:06 AM »
I'm wondering though, how the line widths/ picture height (LW/PH) figures from lense tests translate to sensor resolution.
So 18MP result in 3456 "lines per picture height", while the highest LW/PH scores for APS-C I found were around 2600. If this was a 1:1 conversion, no APS-C sensor above 12MP would be of much use. So I'm guessing that's probably not it. I'd like to find a way to calculate the corresponding sensor resolution to any given lens resolution (and vice versa) OR know why this is not possible. Can anyone help?
If you apply the Nyquist theorem you'll figure out you need at least double the number of sensor cells to resolve lines (you need at least a bright row of pixels followed by a dark row of them to actually have lines and not a solid area). And this is not even considering that almost all sensors are bayer patterned, for which the rule of thumb stipulates you have about 75% of luma resolution after de-bayering. In short: A sensor with 1000 height cells is able to resolve about (1000*0.75)/2 = 375 lines.

EDIT: I left out further resolution losses incurred by the optical low pass filter, which is necessary to avoid aliasing (the artifact that appears once you go beyond the barrier established by Nyquist), but has less than ideal characteristics due to design constraints.
« Last Edit: February 14, 2012, 04:33:39 AM by Rav »

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #42 on: February 14, 2012, 06:15:13 PM »
I'm wondering though, how the line widths/ picture height (LW/PH) figures from lense tests translate to sensor resolution.
So 18MP result in 3456 "lines per picture height", while the highest LW/PH scores for APS-C I found were around 2600. If this was a 1:1 conversion, no APS-C sensor above 12MP would be of much use. So I'm guessing that's probably not it. I'd like to find a way to calculate the corresponding sensor resolution to any given lens resolution (and vice versa) OR know why this is not possible. Can anyone help?


If I understand how your measuring LW/PH, then an 18mp APS-C sensor resolves the same as an 18mp FF...both the 7D and the 1D X produce images that have 3456 lines. Generally speaking, a more tech-agnostic way to measure resolution is with lp/mm, or line pairs per millimeter (its important to use the term line pair, which denotes the waveform nature of spatial frequencies, a light line (white) followed by a dark line (black)...for camera sensors, line pairs generally need an MTF of 50% contrast, or not fully resolved but about half way there...to be clearly imaged as a full "line pair"...anything less and you are losing resolution to diffraction). In that respect, the highest resolution APS-C's are able to resolve more detail than an 18mp FF sensor, which is exactly correct...the 7D (or for that matter the Sony A77 @ 24mp APS-C) is a higher resolution sensor from the level of fineness of detail resolved than the 1D X...its just in a smaller package with a crop factor. In resolvable lp/mm, an 18mp APS-C sensor can resolve 115.97 lp/mm (3456 lines/14.9mm sensor height = 231.94 l/mm, divide by two to get lp/mm). The 18mp FF sensor of the 1D X, however, can resolve 72 lp/mm (3456 lines/24mm sensor height = 144 l/mm, divide by two to get lp/mm). It is possible to derive the necessary FF megapixels that would produce the same fineness of detail as an 18mp APS-C sensor if you were interested. Take the height and width of the APS-C, calculate the lp/mm for both dimensions, and derive the image width and height for FF from that by multiplying by the correlated sensor dimensions:

 3456L/14.9mm = 231.94 l/mm
 5184L/22.3mm = 232.47 l/mm

 231.94 l/mm * 24mm = 5566 L
 232.47 l/mm * 36mm = 8368 L

 5566 * 8368 = 46,576,288 pixels ~= 46.6mp

You would need a 47mp FF sensor to capture the same lp/mm, or "resolution", as an 18mp APS-C sensor. For reference, the 36.3mp Nikon D800 sensor resolves about 102.3 lp/mm, so even though it has greater megapixels than an 18mp 7D, the 7D is still resolving slightly more detail at a pixel level (barring any intrusive factors such as sensor noise...can't say exactly how the noise of the D800 will be in real-world tests.)

The story is not quite as cut and dry as that, given that (excluding Foveon) most sensors are bayer arrays, usually with a low pass filter in front of them, so that mucks with the final resolution a little bit, and makes it tough to nail down nyquist limit...but from a theoretical standpoint, there you have it.

As for correlating sensor resolution to lens resolution, thats exactly what MTF charts are for, to measure the resolution of independent aspects of an optical imaging system or optical imaging systems as a whole. If you want a handy table that correlates diffraction-limited lens resolution with sensor resolution, the last table of this Luminous Landscape article "Do Sensors 'Outresolve' Lenses?" probably has what your looking for (at least from a theoretical standpoint): http://www.luminous-landscape.com/tutorials/resolution.shtml. You would need to do your own tests on any given lens to determine whether a lens resolves enough detail for a sensor or not. When it comes to Canon's newer lenses (the Mark II's and new designs released in recent years), they are really starting to push the envelope on resolution for common apertures (i.e. f/8) which essentially means...outside of the corners...they are indeed "diffraction limited", and for those apertures the chart in the LL article would apply quite nicely.
« Last Edit: February 15, 2012, 01:51:09 AM by jrista »
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #42 on: February 14, 2012, 06:15:13 PM »

Leon

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #43 on: February 16, 2012, 04:54:22 AM »
jrista:
Quote
It is possible to derive the necessary FF megapixels that would produce the same fineness of detail as an 18mp APS-C sensor if you were interested.

Yes, well I do have the math for that here already, it's not what I meant. I might have gotten a little confused about the right terminology. I'll attach a table with the numbers for a couple of cameras.
That article you posted will take me some time to read through, but I bookmarked it, so thanks!

rav:
Quote
A sensor with 1000 height cells is able to resolve about (1000*0.75)/2 = 375 lines.

Ok, now I'm still not sure what to do with that formula to get to my goal.
Let's have a look at these MTF charts:

Canon 50/1.4 on 350D (350D is APS-C and has 2304 height cells):


Canon 50/1.4 on 50D (50D is APS-C and has 3168 height cells):


Canon 50/1.4 on 5D2 (5D2 has 3744 height cells):


Now these MTF figures were derived from images that were taken with 8MP and 15MP (APS-C) and 21MP (FF) bodies. Comparing the 350D and 50D figures, they look kinda (oh well...) the same except being cut off at some point (around 2050) by the 350D. Now that cut-off-point, could that be 2304 height cells minus the AA-filter effect?

The question remains: Are these charts in any way helpful on determining if a sensor with a given pixel size (e.g. 4,31µm) will be outresolved by a certain lens at a certain setting?

Also, given this situation: A certain lens (lets say the 50/1.4) is tested on a certain body (350D). The MTF figures at a certain setting (1.8 ) are clearly lower (1850 LW/PH) than the maximum the camera can resolve (lets say 2050 LW/PH for the 8MP 350D). Can we assume that a higher resolution sensor of the same physical size will not give us any more picture detail? I know the charts above say differently - but why?
(OR could that be due to inaccurate measuring (the tests were a couple of years apart) or assembling deviations (no two lenses are the same)?)

Again, what I found was, that when you take an 18MP picture with the 50/1.4@1.8 on an APS-C camera, downscale it to 8MP and reupscale it to 18MP, there is no loss of detail (at all). Thats why I figured that this lens @1.8 doesnt even outresolve an 8MP APS-C sensor, which I think is supported by the MTF figures above.
« Last Edit: February 16, 2012, 05:41:11 AM by Leon »

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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #44 on: February 16, 2012, 10:29:36 AM »
rav:
Quote
A sensor with 1000 height cells is able to resolve about (1000*0.75)/2 = 375 lines.
Ok, now I'm still not sure what to do with that formula to get to my goal.
Let's have a look at these MTF charts:

I think rav is multiplying by 0.75 to account for bayer array nuances and low-pass filter effect. That would be a fairly rough way to account for those factors, and maybe a little excessive, but its a start.

Quote
Now these MTF figures were derived from images that were taken with 8MP and 15MP (APS-C) and 21MP (FF) bodies. Comparing the 350D and 50D figures, they look kinda (oh well...) the same except being cut off at some point (around 2050) by the 350D. Now that cut-off-point, could that be 2304 height cells minus the AA-filter effect?

It could be partly the AA (low-pass) filter, which does indeed do some blurring. Generally speaking, a well-designed low-pass filter will not really blur an image much...the point is to cut off spatial frequencies that are already below what the sensor can usefully resolve anyway. Removing a low-pass filter will generally result in more noise at very high frequencies below the nyquist limit of the sensor, so by "blurring" those frequencies helps prevent adding more noisy information to the image, thereby preserving frequencies that CAN be usefully recorded by the sensor. A low-pass filter should improve IQ when used correctly, not reduce it, but its a fine line, and at least with more recent Canon cameras, the low-pass filters seem to be just a tad over-aggressive.

Quote
The question remains: Are these charts in any way helpful on determining if a sensor with a given pixel size (e.g. 4,31µm) will be outresolved by a certain lens at a certain setting?

Yes...there are several tables in the Luminous Landscape article I linked that will either tell you that information strait up, or help you derive such information yourself...from a theoretical standpoint. From a real-world standpoint, there are a lot of factors involved related to both the sensor and the lens that affect resolution, many of which can be difficult to evaluate from an objective standpoint. You can roughly approximate whether a lens is outresolving a sensor or whether a sensor is outresolving a lens at any given aperture setting, but it will never be exact without extensive testing.

Quote
Also, given this situation: A certain lens (lets say the 50/1.4) is tested on a certain body (350D). The MTF figures at a certain setting (1.8 ) are clearly lower (1850 LW/PH) than the maximum the camera can resolve (lets say 2050 LW/PH for the 8MP 350D). Can we assume that a higher resolution sensor of the same physical size will not give us any more picture detail?

If we assume that the 50/1.4 is a perfect lens, such that it has no optical aberrations or problems with flare (a physical impossibility, but lets assume for discussion sake for the moment), then yes...until you reach the physical limit of resolution for the 50/1.4 at f/1.8, a higher resolution sensor of the same physical size will continue to resolve more detail. A perfect 50mm lens at f/1.8 could probably resolve around 375lp/mm. Assuming an APS-C sensor, you would need 187mp, or dimensions of 16725x11175 pixels, to resolve 375lp/mm. Such a lens, however, is going to be overpowered by optical aberrations at that aperture, as well as at f/1.4, and probably enough at f/2 that it is still aberration limited. It wouldn't be until f/2.8 or maybe f/4 that the lens becomes diffraction limited, or where aberrations and diffraction have roughly an equal effect. At f/4 the lens could resolve about 173lp/mm, in which case the maximum useful sensor resolution at APS-C would be about 40mp, or 7716x5155 pixels.

If we use the numbers in your charts, it does indeed appear that the 50/1.4 lens becomes diffraction limited around f/4. The 350D peaks at a resolution of 2064 lw/ph, 50D at 2598 lw/ph, and the 5DII peaks at 3740 lw/ph. Thats 90%, 82%, and 99.9% of the maximum capabilities of each sensor. Would make you think the 5D II is resolving more detail...but that wouldn't actually be correct, interestingly enough. Lets convert the resolutions of each sensor from lw/ph to lp/mm:

50D = 106lp/mm
5DII = 78lp/mm
350D = 76lp/mm

Of the three cameras, the 50D actually has the highest resolving power, followed by the 5D II and then the 350D. Given that, the fact that the 50D resolves less of its picture height than the rest by percentage, one of a few things could be wrong: a) the 50D has an aggressive low-pass filter that is affecting resolution more than on the other cameras, b) that the lens was not focused perfectly...it may have been front or back focused ever so slightly, c) the copy of the 50/1.4 used in that particular test was not a great copy. The fact that the 5D II resolves more of its picture height than the 350D is not surprising in the least, given the difference in camera and quality grade between those two...one is a bottom-line consumer grade camera while the other is a top of the line professional grade camera. Resolving 99.9% of what its capable of is damn good, and probably slightly better than expected for a camera of its caliber and price.

The EF 50mm f/1.4 lens has an MTF chart that indicates the lens has high contrast but acceptable resolution. Even at its ideal aperture, which appears to be f/4, this lens is not going to resolve as much detail (lp/mm) as a perfect lens. Its about 65% of the way there at worst, and 87% there at best, or 76% on average. Rav's computation would be roughly accurate for this lens, Apoligies, I used the wrong MTF chart before. Its about 50% resolution at worst, 86% at best, or on average 68%.  This indicates that an 18.4mp APS-C sensor would be the highest resolution it could reasonably resolve to before the sensor starts consistently outresolving the lens at all apertures.

Quote
I know the charts above say differently - but why?
(OR could that be due to inaccurate measuring (the tests were a couple of years apart) or assembling deviations (no two lenses are the same)?)

If the tests were done years apart, then there are certainly questions about the accuracy and consistency of the combined results. If the same exact lens was not used in all three tests, then you have to suspect the quality and calibration of each lens, and whether the lenses and cameras were calibrated to each other for maximum performance. The 5D II and possibly 50D (can't remmber off the top of my head) offer microfocus adjustment, which can largely correct front/back focus problems. Without proper adjustment and tuning of each lens to the camera body its used on, a significant portion of margin of error would have to be attributed to the lens. I think that could easily account for the discrepancy with the 50D, which has the highest resolution sensor of all the cameras tested.

Quote
Again, what I found was, that when you take an 18MP picture with the 50/1.4@1.8 on an APS-C camera, downscale it to 8MP and reupscale it to 18MP, there is no loss of detail (at all). Thats why I figured that this lens @1.8 doesnt even outresolve an 8MP APS-C sensor, which I think is supported by the MTF figures above.

You are absolutely correct, at f/1.8 optical aberrations are going to greatly overpower diffraction, so the sensor would indeed outresolve the lens at f/1.8. However if you stopped the lens down to f/4, and had it properly calibrated for your particular camera body by using microfocus adjustments (and possibly sending both in for proper calibration by a Canon service rep if microfocus doesn't correct all missfocus problems), then I would expect the 7D to resolve the maximum amount of detail the 50/1.4 is capable of resolving at the center. Corner sharpness drops off drastically, and its unlikely the 50/1.4 would outresolve the 7D at any aperture except maybe f/4.
« Last Edit: February 16, 2012, 01:28:47 PM by jrista »
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Re: 36+ Mp EOS dSLR (rumored): How do existing EF lenses cope?
« Reply #44 on: February 16, 2012, 10:29:36 AM »