f-stop limits for full sensor resolution

[BJL]

Ray, indeed I meant at f/11.

Of course at equal f-stop, diffraction is equal, but in practice choices often need to be made between different apertures, for the sake of best overall resolution/sharpness depending on
- diffraction (better at larger apertures)
- aberration effects (better at smaller apertures almost certainly, but in a way that is less predictable)
- out of focus effects on sharpness (better at smaller apertures: I am talking specifically about image resolution only, not artistic blurring of backgrounds and such.)
As soon as such balancing is needed, it is pointless to focus on reducing one source of imperfection to negligible levels.

Since you have still offered no useful answer to my question, let me restate it again.

What is the practical relevance of knowing "at which f-stops a lens's resolution is determined mostly by diffraction", beyond what is revealed more directly and in more detail by overall measurements of resolution such as MTF charts or l/mm at which MTF is 50%?

- It it not useful when choosing between different f-stops for the sake of optimal resolution: just looking at which f-stop gives the best resolution answers that question, even if at that optimal f-stop, aberration is significant.

- It is not needed and not particularly useful when comparing the resolution of two lenses: again directly examining their resolution at various f-stops is a more direct and informative way to do that.

- But maybe is it useful in predicting how far it is worth increasing sensor resolution (in 35mmFF say), but even then overall MTF data is probably more useful.

For example, if few or no 35mm lenses can offer resolution better than can be attained at f/8 with a diffraction limited lens, then lenses limit resolution more than 35mmFF sensors once pixel spacing is below about 8 microns, suggesting that resolution gains in 35mm format will be rather limited if pixel spacing moves much below the current minimum of 7.2 microns in the 1DSMkII.

(Smaller format sensors using the same lenses are exempted, since the PhotoDo MTF measurements you cite average over various parts of the 35mm frame, so average MTF could be significantly higher over only the smaller frames of most DSLR's that use 35mm format lenses.)


This makes me wonder how you expect your "not diffraction limited at less than f/8" lenses will look when used on an imagined 35mm format DSLR with the 5.5 micron pixel spacing of the Nikon D2X sensor.

I wildly predict that we will never see substantially more than about "20MP worth" of resolution in 35mm format, due to you bad news about 35mm format lens resolution , except perhaps in very expensive, low volume bodies only worth using with a collection of mostly very expensive and as yet non-existent super-lenses. (Higher pixel counts might arise for other purposes, like cropping to the sufficiently sharp part of the frame for extra telephoto/macro reach, or to help reduce moire by "oversampling".)

[Ray]

Since you have still offered no useful answer to my question, let me restate it again.

What is the practical relevance of knowing "at which f-stops a lens's resolution is determined mostly by diffraction", beyond what is revealed more directly and in more detail by overall measurements of resolution such as MTF charts or l/mm at which MTF is 50%?

BJL,
Knowing that a lens is diffraction limited at a particular f stop gives one the confidence that no lens can be better, at that f stop. Photodo's statement that all (35mm) lenses are equally bad at f11 is not actually true, I'm sure you'll agree.

There are some zooms that at certain focal lengths are actually sharpest at f16, at which aperture such a lens probably is diffraction limited. If I had such a zoom, I'd definitely like to know that the lens at that particular FL is not diffraction limited at f11, wouldn't you?

Of course, if you already have possession of all the measurements at all the f stops you are likely to use, either in terms of Photodo type MTF charts, or lp/mm at 50% MTF, then knowing which f stop is diffraction limited is of more academic interest, but perhaps with some very pratical economic implications.

For example, if I know that a particular lens which I use frequently at f11 is actually diffraction limited at f11 pretty much out to the edges of the frame, then I can stop looking around for a better lens, and possibly save some money   .

For example, if few or no 35mm lenses can offer resolution better than can be attained at f/8 with a diffraction limited lens, then lenses limit resolution more than 35mmFF sensors once pixel spacing is below about 8 microns, suggesting that resolution gains in 35mm format will be rather limited if pixel spacing moves much below the current minimum of 7.2 microns in the 1DSMkII.

You've lost me here, BJL. If it's true that a lens, diffraction limited at f8, can deliver 97 lp/mm at 50% MTF, then such a lens would probably (but not necessarily) improve upon that figure at wider apertures. Canon's current highest resolving DSLR, the 400D with 5.5 micron spacing only resolves around 61 lp/mm (at presumably 10% MTF), according to dpreviews 'lines per picture height tests'. That's a far cry from 97 lp/mm at 50% MTF and an even further cry from the 120 lp/mm that we could expect at f4 from such a lens which is diffraction limited at f8.

[Ray]

I always like to back up my theoretical pronouncements with some hard visual facts, if possible, so I took the trouble to test my 50/1.4 at f8, f11, f16 and f22 on my own test board consisting of Norman Koren line charts plus various textured surfaces stuck on a piece of plywood.

I was already aware that the resolution differences between f8 and f16 with a zoom lens like the 24-105 on my 5D were too subtle to bother with, for landscapes.

What surprised me was just how similar the differences were with the 20D, which is in effect a cropped 22mp FF camera.

Here is the comparison. All shots were taken on tripod, with remote release and mirror lock-up (would I do anything less?)

[attachment=2394:attachment]

To my eyes, there's no difference between f8 and f11. At f16 there's a very marginal fall in clarity but still not a major concern. The softness at f22 is pretty obvious. I wouldn't use this f stop unless maximum DoF was paramount.

So what conclusions can we derive from these results? Let's examine the unknowns as well as the knowns.

(1) The 50/1.4 is not diffraction limited at its sharpest f stop of f8. There's room for improvement.

(2) The 50/1.4 might be diffraction limited at f11, but if it is, a 22mp FF sensor is not able to tell us.

Conclusion: A 22mp FF sensor has not even sufficient pixel density to capture the resolution potential of existing 35mm lenses, never mind future lenses.

[bjanes]

I always like to back up my theoretical pronouncements with some hard visual facts, if possible, so I took the trouble to test my 50/1.4 at f8, f11, f16 and f22 on my own test board consisting of Norman Koren line charts plus various textured surfaces stuck on a piece of plywood.

What surprised me was just how similar the differences were with the 20D, which is in effect a cropped 22mp FF camera.

Here is the comparison. All shots were taken on tripod, with remote release and mirror lock-up (would I do anything less?)

To my eyes, there's no difference between f8 and f11. At f16 there's a very marginal fall in clarity but still not a major concern. The softness at f22 is pretty obvious. I wouldn't use this f stop unless maximum DoF was paramount.

So what conclusions can we derive from these results? Let's examine the unknowns as well as the knowns.

(1) The 50/1.4 is not diffraction limited at its sharpest f stop of f8. There's room for improvement.

(2) The 50/1.4 might be diffraction limited at f11, but if it is, a 22mp FF sensor is not able to tell us.

Conclusion: A 22mp FF sensor has not even sufficient pixel density to capture the resolution potential of existing 35mm lenses, never mind future lenses.
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Ray,

I'm happy that people were not reading my posts carefully, since in my previous post of the Imatest results with the Canon EOS 1Ds MII I inadvertently forgot to convert from lines/mm to line pairs/mm and the results looked much closer to ideal than they should. The Nyquist limit of the 1Ds MII is 69.3 lp/mm. I reposted the correct results in the original post and am repeating the chart here. As you correctly observe, the system resolution does not approach the diffraction limited resolution of the lens, but nonetheless, the results are quite good and Michael frequently talks about his sensor out resolving the lens.  How than this be?

[attachment=2407:attachment]

I think the answer if found in consideration of the SQF data and concept. According to SQF, the eye is most sensitive to contrast in the frequency range of 3-12 cycles per degree as seen on the print as viewed from the observation distance. For an 8 by 10 inch print, the critical resolutions are from 4 to 16 lp/mm on a 35 mm negative or with a full frame sensor (8 times enlargement) and 8 to 32 lp/mm for a 16 by 20 inch enlargement. With proper sharpening, the MTF of the camera is quite good in this range as demonstrated by the Imatest SQF plot. Higher frequencies are not resolved by the camera, but these are not critical for perceived image sharpness.

[attachment=2406:attachment]

In your tests with Norman Koran's resolution chart, the MTF in these critical frequencies is not readily determined by examination with the naked eye. I downloaded your images and used PixelProfile as suggested by Mr. Koren to estimate the MTF in the region of 40 to 100 lp/mm in the test images.

[attachment=2408:attachment]

[attachment=2409:attachment]

As is apparent from inspection of the test shots, there is only aliasing beyond the Nyquist limit of 78 lp/mm, but MTF resolution at f/22 in the important lower frequencies is limited.

[Ray]

As you correctly observe, the system resolution does not approach the diffraction limited resolution of the lens, but nonetheless, the results are quite good and Michael frequently talks about his sensor out resolving the lens.  How than this be?

Bill,
As you know, we can't really expect the system resolution to approach the diffraction limited resolution of the lens because system resolution is always some sort of product of both sensor resolution and lens resolution, the result always being less than either sensor or lens resolution taken separately. This is why I prefer MTF charts of lens-only performance. I buy my lenses separately to the camera body. I use the same lenses on different formats with significantly different pixel densities and I hope to continue using such lenses with future DSLR models. I therefore want to know the performance of the actual lens itself, not just a diluted performance in conjunction with a particular DSLR.

This concept of sensor outresolving lens should really be defined, as all terms should be. The only sensible definition I can think of is when the sensor (or film), when tested separate from the lens, delivers better specs than the lens.

For example, if a lens can resolve 40 lp/mm at 70% MTF but the sensor can resolve 40 lp/mm at 80% MTF, then there's a reasonable case to be made that the sensor is outresolving the lens.

I always remember the specs of T-Max 100 B&W film because the MTF response was so amazing compared with color film, being 100% up to 50 lp/mm and 60% at 100 lp/mm (according to Kodak). No lens can match this, so I think it would be fair to say that T-Max 100 really does (did) outresolve the lens (except for that bloody grain   ) .

As far as I can see from the available evidence, there are no DSLRs which can outresolve 'good' prime lenses in the central area of the image circle, which is roughly covered by the cropped formats.

The grey area is between the edges of the cropped format and the edges of the FF sensor. In this area of the image circle, one could say that all of Canon's FF DSLRs are outresolving all but the best lenses.

In your tests with Norman Koran's resolution chart, the MTF in these critical frequencies is not readily determined by examination with the naked eye. I downloaded your images and used PixelProfile as suggested by Mr. Koren to estimate the MTF in the region of 40 to 100 lp/mm in the test images.

Bill, I have a problem with this approach. In one breath you are talking about SQF and in another your are expounding on the opposite. What cannot be determined with the naked eye is surely only of academic interest. If the naked eye cannot determine relevant differences in a 200% enlargement on screen, which represents a huge print, probably about 6ft x 9ft (I haven't calculated), then why should we bother?

As is apparent from inspection of the test shots, there is only aliasing beyond the Nyquist limit of 78 lp/mm, but MTF resolution at f/22 in the important lower frequencies is limited.

Only aliasing beyond the Nyquist limit? How can that be? I thought it was only the Foveon type sensor which could reach resolution to the Nyquist limit? This is the explanation for a 3.3MP Foveon sensor equalling the resolution of a 6mp Bayer type sensor.

[BJL]

Knowing that a lens is diffraction limited at a particular f stop gives one the confidence that no lens can be better, at that f stop.
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If you consider having such confidence to be of practical importance, then fine.

To refine my comments about lens resolution limits on the pixel sizes that will be worthwhile in 35mm format:

Firstly, I was talking about what I have seen (and heard from you) about actual lenses, not hypothetical ones that are purely diffraction limited at f/8.

Mainly, my rough reading of MTF curves is that for lenses other than very good and very long telephotos, the fall-off from center to edge is greater than the improvement on-axis in going from f/8 to any smaller f-stop. If so, then off-center performance at any f-stop is less than on axis performance at f/8 and so in turn worse than the limits set by diffraction alone at f/8. So once one cares about sharpness across a significant fraction of the 35mm frame (not, say, just with an "APS-C" crop), the lens resolution limit is probably not a lot less than around what 8 micron pixel spacing gives. At a very rough estimate, I doubt that the 5.5 micron pixel spacing of the D2Xs will ever have much use in 35mm format, and even less so the 4.7 micron spacing of the new Panasonic nMOS 10MP 4/3" sensors.

[bjanes]

This concept of sensor outresolving lens should really be defined, as all terms should be. The only sensible definition I can think of is when the sensor (or film), when tested separate from the lens, delivers better specs than the lens.

For example, if a lens can resolve 40 lp/mm at 70% MTF but the sensor can resolve 40 lp/mm at 80% MTF, then there's a reasonable case to be made that the sensor is outresolving the lens.
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Ray,

It's not that simple. In your example you mention 40 lp/mm as a reference point, but other frequencies also come into play. As you know, MTF curves for lenses start out at 100% and fall to zero. What happens between these extremes is important. MTF at 10 lp/mm (good contrast) is often considered more important in 35 mm photography than at 40 lp/mm (resolution).

By the process of Reductio ad absurdum , with your line of reasoning, one could say that lens choice is not important for digital cameras since even a cheap lens will out resolve the camera. However, a good lens will often give better contrast at the important lower frequencies.

Bill, I have a problem with this approach. In one breath you are talking about SQF and in another your are expounding on the opposite. What cannot be determined with the naked eye is surely only of academic interest. If the naked eye cannot determine relevant differences in a 200% enlargement on screen, which represents a huge print, probably about 6ft x 9ft (I haven't calculated), then why should we bother?
[a href=\"index.php?act=findpost&pid=115114\"][{POST_SNAPBACK}][/a]

MTF and SQF complement each other. Whenever you reduce a complicated measurement to one number, you are losing information in the process of simplifying things. However, both are relatively objective and reproducible. In contrast, the naked eye is highly non-reproducible and subjective. Remember David Pogue's essay in the  New York Times where observers could not tell a 6 from a 22 MP image?

Your pixel peeping approach determines detail at high frequency, but not at the important lower frequencies. To evaluate the lower frequencies, one must stand back and inspect the overall image.

Only aliasing beyond the Nyquist limit? How can that be? I thought it was only the Foveon type sensor which could reach resolution to the Nyquist limit? This is the explanation for a 3.3MP Foveon sensor equalling the resolution of a 6mp Bayer type sensor.
[a href=\"index.php?act=findpost&pid=115114\"][{POST_SNAPBACK}][/a]

Bayer array sensors resolve about 70-80 percent of the Nyquist limit at low contrast, as can be seen by looking at the resolution tests on DPReview. However, as Norman Koren states, it does not make sense to measure resolution at the point where detail disappears. The DPReview tests are not informative: one can always say 75% of Nyquist without even looking at the test results. Aliasing will occur only above the Nyquist limit and is manifested by false detail. At and slightly below Nyquist, the Bayer sensor will show no useful detail.

Bill

[Ray]

Firstly, I was talking about what I have seen (and heard from you) about actual lenses, not hypothetical ones that are purely diffraction limited at f/8.

Mainly, my rough reading of MTF curves is that for lenses other than very good and very long telephotos, the fall-off from center to edge is greater than the improvement on-axis in going from f/8 to any smaller f-stop. If so, then off-center performance at any f-stop is less than on axis performance at f/8 and so in turn worse than the limits set by diffraction alone at f/8. [a href=\"index.php?act=findpost&pid=115126\"][{POST_SNAPBACK}][/a]

BJL,
The problem here is that there's no information on the performance of Canon lenses at 60 & 70 lp/mm, the sorts of resolutions that FF sensors of 22mp and beyond should be able to record if the MTF at such resolutions is high enough.

However, there are a few lenses ranging from 50mm to 400mm that can resolve 40 lp/mm at 70% almost to the corners, according to Photodo test results. The cheapest of these is the 50/1.4 which, at f8, has a flat response of 70% out to 18mm from the centre. Some lenses such as the 135/2 fall only to 60% at the very corners.

Considering that the extreme corners are usually not significant in most compositions and especially not significant in shots where shallow DoF is sought, and considering the SQF criteria that Bill refers to, where good performance at 40 lp/mm would be the main requirement for sharp looking prints of 22"x33", I see no reason why good current lenses will not be up to the job.

However, because of QC lens variation, I would prefer that all lenses have a thorough MTF test, carried out either by the manufacturer or an approved agent, before being sold to the public. Such lenses should ship with detailed MTF results at a number of frequencies and should be graded and priced accordingly.

The astute buyer would then be in a position to select the grade of lens that best suits his/her requirements.

[Ray]

It's not that simple. In your example you mention 40 lp/mm as a reference point, but other frequencies also come into play.

Bill,
Not as a reference point; merely as an example. The example can apply to as many frequency points you think necessary.

By the process of Reductio ad absurdum , with your line of reasoning, one could say that lens choice is not important for digital cameras since even a cheap lens will out resolve the camera. However, a good lens will often give better contrast at the important lower frequencies.

Not at all. That's not what I'm saying. Good lenses will always impart a certain quality to the image whatever the pixel density. I'm saying that a high pixel density sensor with even a modestly cheap lens, will deliver a sharper image than a low density sensor, at least in the central area of the image circle.

A high pixel density sensor will also deliver a sharper image with a very expensive lens, but perhaps also an even sharper image than the cheap lens, a higher contrast image and a better looking image in ways that sometimes might be difficult to define.

MTF and SQF complement each other. Whenever you reduce a complicated measurement to one number, you are losing information in the process of simplifying things.

I have no intention of simplifying things till they become meaningless. Let it all hang out, as long as it's relevant.

Bayer array sensors resolve about 70-80 percent of the Nyquist limit at low contrast, as can be seen by looking at the resolution tests on DPReview.

I thought the dpreview resolution tests were of high contrast line charts??

[bjanes]

I thought the dpreview resolution tests were of high contrast line charts??
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They are, but at 10% MTF they become low contrast.  

Bill

[Ray]

They are, but at 10% MTF they become low contrast.   

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Then we have to wonder how lens resolution of 60 lp/mm and (say) 50% MTF becomes 60 lp/mm at a mere 10% MTF on a 20D which is effectively a cropped 21mp FF sensor. Is this due principally to lack of pixel density or too much read noise?

[BJL]

BJL,
The problem here is that there's no information on the performance of Canon lenses at 60 & 70 lp/mm...

However, there are a few lenses ranging from 50mm to 400mm that can resolve 40 lp/mm at 70% almost to the corners, according to Photodo test results. The cheapest of these is the 50/1.4 ...

... considering the SQF criteria that Bill refers to, where good performance at 40 lp/mm would be the main requirement for sharp looking prints of 22"x33"
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On the first point I agree that I am speculating by extrapolation from inconclusive data.

On the second, there are probably some lenses sharp enough to make good use of 30MP+, but I suspect too few for all but a rather special class of photography. Another guess of mine is that if the best standard zooms cannot make use of extra resolution, the market for it probably gets very small. But maybe still enough for one very high and 30MP model atop already very good 16-20MP high end models.

But what if you are right about 40 lp/mm being enough for sharp 22"x33" prints? Such resolution is probably comfortably provided already by the 16.5MP 1DsMkII sensor, so why push on to 5.5 micron pixel spacing, probably good for about 60lp/mm?

Canon talked a while ago about plans for some new higher resolution lenses (the first of which is the 16-35/2.8 II, it seems) for those who want high quality 13x19 prints.  What lp/mm and pixel density do you think is needed for that goal, more modest than the 22"x33" you mention?

[Ray]

On the second, there are probably some lenses sharp enough to make good use of 30MP+, but I suspect too few for all but a rather special class of photography. Another guess of mine is that if the best standard zooms cannot make use of extra resolution, the market for it probably gets very small. But maybe still enough for one very high and 30MP model atop already very good 16-20MP high end models.

I'm an optimist here. We know that QC variation in most (if not all) models of lenses is a serious problem. When people complain about their lenses not being good enough, I suspect that more often than not, it's simply due to the luck of the draw. They've got a dud, or at best a lens that falls into the lower 50% of the manufacturer's acceptable quality range. There's always a range for acceptable quality, set by the manufacturer.

My proposal is, let the consumer set the preferred range. Provide them with the information and let's see if the customer will pay a 50% premium for a lens that has sterling performance right to the edges, or a 20% premium for a lens of the same model that has moderately good performance to the edges.

There have been some disappointing reports of the new Canon 16-35. Who knows if such reports are due to QC variation. The consumer is being treated as a sucker. We're in the age of measurement. Even my 22 year old pair of loudspeakers (Celestion SL600) came with individual frequency response charts for each speaker.

What's the problem here? Beats me.

But what if you are right about 40 lp/mm being enough for sharp 22"x33" prints? Such resolution is probably comfortably provided already by the 16.5MP 1DsMkII sensor, so why push on to 5.5 micron pixel spacing, probably good for about 60lp/mm?

Micro detail. SQF is really a blunt instrument. Contrast at 40 lp/mm might well have an important effect on the perception of over-all sharpness in a 22x33" print, but those small leaves, high up in the tree need at least 70 lp/mm.

[Claude Jodoin]

These results more or less confirm the general consensus that f11 is the limit for stopping down with cropped 35mm format and and f16 the limit for full frame 35mm. Standard 50mm lenses are usually very sharp at f5.6 - f8. With the average zoom lens, the differences between f5.6 and f11 would be less.

Perhaps more relevant than using Imatest is to do real world comparisons with specific lenses. I've done extensive 'real world' comparisons of my 5D with 24-105 zoom and there's no significant resolution difference between f8 and f16, at the plane of focus. I haven't however done similar comparisons using my sharpest lens, the Canon 50/1.4.
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I was one of the "magnificent 7" photographers, brought to Foveon by the late, great, Dean Collins. He created the mentor program for the development of the original Prism Camera.

I had 6 different cameras from 1999-2001  and I can say, without any doubt, from a techno-geek perspective that the f/5.6-f/11 statement is true. The Foveon had a 6 micron well site pitch and optimum lens performance, verified by me with their chief engineer and optical enginneer, with all kinds of test targets was in that range.

The only time I was able to get any sort of moire pattern out of the Foveon (No moire was their claim to fame vs. the original Phase One Lightphase of the day) was at f/6.3. This turned out to be the peak MTF for the glass, allowing a sympathetic frequency of the clothing pattern against the well site pitch of the 3 chips micro-aligned onto a dichroic prism. Otherwise, the inability of the lens to reach 83 LPMM (required to resolve 6 microns) at other apertures made the lens act (effectively) as a low pass filter. Color aliasing was non existent since the 3 chips had full color sampling at every pixel, a Carver Mead philosophy which persists, even today in the lates Foveon X3 chips.

Claude Jodoin
Tech. Editor
Rangefinder/After Capture Mag.

[Claude Jodoin]

I forgot to mention that the camera had no moving parts. Only the aperture and focus motor in the lens moved. It could synch. to ANY studio flash at up to 1/8000 of a second, since it had an all-electronic shutter.

Planned obsolescence via electro-mechanical shutter wear persists today.

Claude Jodoin
Tech. Editor
Rangefinder/After Capture Mag.

[Ray]

I had 6 different cameras from 1999-2001  and I can say, without any doubt, from a techno-geek perspective that the f/5.6-f/11 statement is true. The Foveon had a 6 micron well site pitch and optimum lens performance, verified by me with their chief engineer and optical enginneer, with all kinds of test targets was in that range.
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Claude,
I imagine that to equal the resolution of a Foveon type sensor with 6 micron spacing, a Bayer type sensor would need spacing even smaller than 5 microns. Right?

Perhaps the only way forward to maximise the full potential of existing 35mm lenses is the development of a full frame Foveon sensor with 6 micron pixel pitch, eventually progressing to 5 microns as better lenses are developed.  

[BJL]

Claude,
I imagine that to equal the resolution of a Foveon type sensor with 6 micron spacing, a Bayer type sensor would need spacing even smaller than 5 microns. Right?
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Right I think. According to both Foveon engineers and other sources including resolution tests I have seen, a Bayer CFA sensor needs about twice the pixel count of an "X3" type sensor to get equal resolution, or a factor about 1.4 in pixel spacing. So about 4 microns for Bayer CFA to match 6 micron X3.

Perhaps the only way forward to maximise the full potential of existing 35mm lenses is the development of a full frame Foveon sensor with 6 micron pixel pitch ...
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There is no fundamental problem making Bayer CFA photosites far smaller than the 4 microns needed to match 6 micron X3 photosites for resolution, or even the 3.5 micron ones needed to match 5 micron X3 photosites. So to claim an advantage for X3, you must assume that the X3 photosites would be superior in some way to Bayer CFA photosites of about half the area. Superior for example in sensitivity, noise levels at equal ISO, dynamic range and such.

Though that might seem intuitive, there is no evidence so far that it is true: the high ISO performance of Foveon's X3 sensors so far seems not to match that of good Bayer CFA photosites of half or less the area.

Perhaps this is because, at least with Foveon's version of X3 detection, far from all of the light of each of the three color ranges is detected by the appropriate layer of the three layer sensor. This is probably because Foveon's approach depends on the differential absorption in silicon of different wavelengths of light, which is very far from the ideal of, say, the top layer absorbing and detecting all blue light while all green and red light passes through, and so on.

Other X3 technologies are apparently being investigated by companies like Fujifilm and Canon, but it seems far too early to predict whether they will ever in fact perform better than the currently dominant Bayer CFA approach.

[BJL]

I'm an optimist here. ...
There have been some disappointing reports of the new Canon 16-35. ...
What's the problem here? Beats me.
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There might be an important point in there. Even with film, there was clearly room for improving overall image quality by improving on the quality of most or all Canon zoom lenses, so presumably Canon already had good reason to work on improving lens resolution. Thus it is unclear that the change to electronic sensors will lead Canon to achieve substantially more than it had already achieved as far as lens resolution, with zooms at least. Perhaps some primes are good enough that little would have been gained with film SLR's by improving them, but there is more room for improvement with current or future sensors of high enough resolution.

And as the 16-35 was the most often mentioned resolution limit of Canon's 35MM FF DSLR system, the most glaring weakness is any aspiration to take over the higher resolution sector previously dominated by medium format and as the new 16-35 is clearly intended as an important part of Canon's stated program of improving resolution limitations in its high end lens system, the "limited success" of that new lens as far as increased sharpness is an indication that 35mm format might already be close to the practical resolution limits of zoom lenses at least.

But I suppose that Canon can compete fairly well against medium format mostly with expensive prime lenses instead. So where are the new, sharper Canon primes, wide angles in particular?

[BJL]

I forgot to mention that the camera had no moving parts... It could synch. to ANY studio flash at up to 1/8000 of a second, since it had an all-electronic shutter.
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So no moving mirror: was this camera was a "rangefinder", with no TTL VF, or did it use a fixed beam splitter (pelicle mirror or such), or a live video viewfinder?

What was its maximum shutter speed and frame rate?

I am waiting for electronic shuttering to arrive in DSLR's, especially for high frame rate action, and for eliminating mirror and shutter vibration when used in conjunction with Live View (as now being offered in DSLR's by Olympus/Panasonic/Leica and Canon, and in a more limited form by Fujifilm.)

[Ray]

Though that might seem intuitive, there is no evidence so far that it is true: the high ISO performance of Foveon's X3 sensors so far seems not to match that of good Bayer CFA photosites of half or less the area.

Perhaps this is because, at least with Foveon's version of X3 detection, far from all of the light of each of the three color ranges is detected by the appropriate layer of the three layer sensor. This is probably because Foveon's approach depends on the differential absorption in silicon of different wavelengths of light, which is very far from the ideal of, say, the top layer absorbing and detecting all blue light while all green and red light passes through, and so on.

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This is my understanding also. However, we should not forget that the Bayer CFA deliberately blocks out a lot of light. Each of those red, green and blue filters is supposed to block out a large portion of the other 2 colors, is it not?

What proportion of light is blocked, do you know? Perhaps not as much as 2/3rds but maybe as much as a half. That doesn't sound particularly efficient to me.