# Lens 'resolving power' vs sensors.



## sanj (Feb 14, 2012)

Hello experts.
I keep hearing that current Canon lenses are not 'good enough' for newer/better sensors. I would really appreciate a lesson on how this works.
Thx...


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## jrista (Feb 15, 2012)

To start, its best to measure resolution in *lp/mm*, or *line pairs per millimeter*. This is a measure of _spatial frequencies_...light/dark oscillations or waveforms that compose a two dimensional image, be that the virtual image projected by a lens, the image recorded by film or a digital sensor, etc. Measurement in line pairs, or a light line paired with a dark line, is essential to measure microcontrast, or the ability to discern the difference between a light line and a dark line that are right next to each other. 

(NOTES: For reference, the human eye is able to discern a line pair when contrast is as low as 9% (this is called _Rayleigh Criterion_). Modern sensors capable of barely resolving detail around the same level, probably closer to 12-15%, however at such levels details can become inconsistent and often "useless". Low-pass filters are usually used to cut off spatial frequencies somewhere below this level to eliminate what effectively becomes additional image noise and possibly moire in the presence of regular repeated patterns. Sensors can only really resolve a line pair as consistently separate light and dark lines when contrast is about 50%. For any imaging medium to resolve a line pair, it must have twice the resolution as the frequency being sampled...so for a sensor to resolve 100 lp/mm, it must have at least 200 rows of pixels per millimeter. This called the _Nyquist Rate_, and the maximum resolution of an image that can be captured...the maximum frequency that can be usefully sampled...is the _Nyquist Limit_.)

Both lenses and sensors have resolution, and they can be measured independently of each other, as well as part of a greater whole. When it comes to sensors, its pretty easy to compute the theoretical resolution. This is usually pretty close, although not exactly the same as, real-world resolution. Real-world resolution can differ a bit when you factor in bayer interpolation, low pass filters, bayer array layout, etc. I'm going to quote from another answer I gave on another topic, as it has relevant information about sensor resolution:



jrista said:


> Leon said:
> 
> 
> > I'm wondering though, how the line widths/ picture height (LW/PH) figures from lense tests translate to sensor resolution.
> ...



Lenses themselves are projecting a virtual image that is simply recorded by the sensor, however the resolution of the image projected by a lens does not have a single "resolution". Depending on the aperture setting, and whether you measure resolution at the center of the lens or the edge of the lens, lens resolution will vary considerably. Assuming an ideal, or "perfect" lens, one that is entirely free of any form of optical aberration, the maximum possible resolution at maximum apertures above f/4 can FAR outresolve current sensors at minimum detectable contrast, and considerably outresolve them at 50% contrast (a key level, as noted above.) 

Perfect lenses are also called "diffraction-limited" lenses, in that the resolution possible is only limited by diffraction and not optical aberrations. Real-world lenses tend to be aberration-limited at wide apertures, and diffraction limited at narrower apertures, and the narrower the aperture, the more diffraction will limit maximum resolution. Thus the reason why a photo will start to soften beyond f/11, and exhibit pronounced degredation beyond f/22, on an APS-C sensor. Because of optical aberrations at wide apertures, lenses exhibit idealistic behavior at middle apertures, such as f/8. However thats just about where things get dicey from a whos-outresolving-who standpoint.

The highest resolution Canon sensor on the market today, their 18mp APS-C sensors, resolve 116 lp/mm (see quote above for reference and details about how this number is derived.) If we assume a perfect lens, at f/2.8 and 50% contrast, you can resolve about 247 lp/mm, which is slightly more than twice what Canon's highest resolution sensors are capable of resolving (for reference, you would need a *210mp FF or 81mp APS-C* sensor to resolve that much detail.) Given that real-world lenses are aberration-limited at wide apertures like f/2.8, lets take a more realistic aperture. The Canon 7D 18mp APS-C sensor is diffraction-limited at f/6.9, so if we assume an f/7.1 aperture, we can resolve roughly around 95-100lp/mm. The sensor is now outresolving the lens at this aperture, and all apertures smaller than f/7.1. At f/8 the lens can only resolve 86 lp/mm, f/11 it drops down to 63 lp/mm, and at f/22 it is at a mediocre 30 lp/mm!! The same lens at f/6.3 would probably resolve just about 118 lp/mm, just ever so slightly better than what the sensor is capable of resolving itself.

When it comes to resolution, its not quite a simple as "Lens A outresolves Sensor A, but Lens B does not". For pretty much any lens these days, at f/8, pretty much all modern sensors with at least 15mp are capable of resolving enough detail to match the lens. Its at wider apertures where lenses have the potential to resolve considerably more detail, and how much more depends on how well aberrations (and flare) are controlled. The more aberration and flare control a lens has, the sharper it will be at wider apertures, and the more likely the lens will be to outresolve even the highest density sensors. 

As for Canon lenses, it depends on what you mean by current. Canon made a claim (I forget where...I've been searching for the reference) that their "newest" L-series lenses, which at the time seemed to mean their Mark II lenses and all "new entrants", or brand new designs like the 8-15mm L Fisheye, are capable of resolving approximately enough resolution for a 45mp full-frame sensor. This accounts for a fair number of lenses released in the last several years, possibly as far back as 2006-2007. I believe a large part of the reason Canon is starting to release more updated lenses, such as the new *24-70mm f/2.8 L USM II*, despite the fact that its predecessor was considered one of their best lenses ever...is to get resolution "up to snuff", and ensure they are capable of resolving enough detail for upcomming (and even current, when accounting for their 18mp APS-C sensors) ultra high resolution sensor designs. 

For top end superteles like the 500mm L II and 600mm L II, given the stunning near-perfect MTF charts, I would effectively consider them "perfect", diffraction limited lenses at all apertures, and therefor capable of about 173 lp/mm at f/4. Thats enough resolution for a *103mp FF* sensor, or a *40mp APS-C* sensor.


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## papa-razzi (Feb 17, 2012)

In non technical terms, what exactly do you mean by "resolving". I have read how the 7D images can look a bit soft at 100% but "resolve" well because there are so many pixels. In this case I assumed "resolved" meant going to 300dpi when printing. You have mentioned lenses resolving to sensors. It all got a bit too technical for me so I'm unclear. I've been wondering what you guys mean by resolve for a while.


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## jrista (Feb 17, 2012)

papa-razzi said:


> In non technical terms, what exactly do you mean by "resolving". I have read how the 7D images can look a bit soft at 100% but "resolve" well because there are so many pixels. In this case I assumed "resolved" meant going to 300dpi when printing. You have mentioned lenses resolving to sensors. It all got a bit too technical for me so I'm unclear. I've been wondering what you guys mean by resolve for a while.



When referring to optical imaging systems...such as cameras, but not limited to them (telescopes, microscopes, etc.), "to resolve" means to "distinguish details", or to make details distinguishable. A lenses power to resolve details in a scene is limited, both by optical aberrations (physical effects caused by lens design, such as chromatic aberration, spherical aberration, field curvature, etc.), and resolving power essentially refers to where that limit lies. 

Regarding the 7D's "softness", there are a few reasons for that. For one, the 7D does seem to have a slightly over-aggressive low-pass filter (AA, or anti-aliasing filter), so it blurs "useful" frequencies that actually represent good detail that can still be imaged by the sensor. Thats not the sole reason for the 7D's perceived softness though. Two additional factors, camera shake and quite literally insufficient lens resolving power, also limit its sharpness when viewing RAW images at 100%. 

The higher the resolution of a sensor, the more important a stable camera is going to be to ensuring pixel-level sharpness. An 18mp APS-C sensor is one of the highest density DSLR sensors on the market, and it resolves an incredible amount of detail (116 lp/mm). Even the slightest amount of camera shake will affect detail, assuming the lens is even resolving enough to start with. 

The extremely high resolution of the 7D also means that outside of the best of the most recent Canon L-series lenses, namely Mark II's and new designs like the 8-15mm L Fisheye, the 7D is very likely outresolving most lenses except for their very centers. Sharpness can fall off quickly from center to corner, particularly in lower-end lenses. Maximum sharpness is often lower than maximum contrast in many Canon lenses as well, so while...for the detail resolved...most Canon lenses offer excellent contrast, sometimes they don't resolve as much detail as is really required for a sensor that offers as much resolution as the 7D. 

(I believe this is why Canon has been releasing updated versions of many of its lenses lately, even those that were previously considered their best lenses ever...like the 24-70mm L. When you compare MTF charts for Mark I and Mark II versions of the same lens, center sharpness is improved somewhat, however corner sharpness is often improved considerably. Its corner resolution where the resolving power of a lens really matters these days with high resolution sensors.)


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## jrista (Feb 17, 2012)

Just for reference, here are the resolutions, in lp/mm (line pairs per millimeter) for the highest resolution sensors on the market for prosumer and professional grade interchangeable lens cameras, ranked in order of physical resolution, not image resolution:

_(Note: Excludes point and shoot or bridge cameras, which may have resolutions as high as 200 lp/mm, but represent an entirely different class of camera.)_

*Nikon v1 Mirrorless 10.1mp CX format*
3872x2592 pixels; 13.2x8.8mm dimensions
Resolution: 147.27 lp/mm

*Sony 24.3mp APS-C "Exmor" HD CMOS*
6000x4000 pixels; 23.5x15.6mm dimensions
Resolution: 128.20 lp/mm

*Olympus E-5 12.3mp Hi-Speed Live 4/3 MOS*
4032x3024 pixels; 17.3x13mm dimensions
Resolution: 116.31 lp/mm

*Canon 7D 18mp APS-C*
5184x3456 pixels; 22.3x14.9mm dimensions
Resolution: 115.97 lp/mm

*Canon 500D 15.1mp APS-C*
4752x3168 pixels; 22.3x14.9mm dimensions
Resolution: 106.31 lp/mm

*Nikon D7000 16.2mp APS-C (DX)*
4928x3264 pixels; 23.6x15.6mm dimensions
Resolution: 104.62 lp/mm

*Pentax K-5 16.3mp APS-C*
4982x3264 pixels; 23.4x15.6mm dimensions
Resolution: 104.62 lp/mm

*Nikon D800 36.3mp Full Frame (FX)*
6144x4912 pixels; 35.9x24mm dimensions
Resolution: 102.33 lp/mm

*Canon 1D IV 16.1mp APS-H*
4896x3264 pixels; 27.9x18.6mm dimensions
Resolution: 87.74 lp/mm

*Nikon D3x 24.5mp Full Frame (FX)*
6048x4032 pixels; 35.9x24mm dimensions
Resolution: 84 lp/mm

*Sony 24.6mp "Exmor" Full Frame*
6048x4032 pixels; 35.9x24mm dimensions
Resolution: 84 lp/mm

*Hasselblad H4D-60 Medium Format Full Frame*
8956x6708 pixels; 53.7x40.2mm dimensions
Resolution: 83.43 lp/mm

*Pentax 645D 40mp Medium Format "Cropped" DSLR*
7264x5440 pixels; 44x33mm dimensions
Resolution: 82.42 lp/mm

*Canon 1Ds III/5D II 21.1mp Full Frame*
5616x3744 pixels; 36x24mm dimensions
Resolution: 78.63 lp/mm

*Canon 1D X 18.1mp Full Frame*
5184x3456 pixels; 36x24mm dimensions
Resolution: 72 lp/mm

*Nikon D4 16.2mp Full Frame (FX)*
4982x3280 pixels; 36x23.9mm dimensions
Resolution: 68.62 lp/mm

From that list, we have the* Nikon D800 36.3mp* sensor as the highest density full-frame sensor on the market, the *Sony 24mp Exmor* sensor as the highest density APS-C sensor on the market, the *Canon 1D IV 16.1mp* sensor as the highest density APS-H sensor on the market (obviously), and the *Olympus E-5 12.3mp* sensor as the highest density 4/3rds format sensor (4/3rds or micro 4/3rds, not sure which it is, as I don't really use that system.) I threw in the Pentas 645D and Hasselblad H4D-60 medium format sensors and the Nikon v1 CX sensor just for a basis of comparison. 

Intriguingly, the Nikon v1 sensor has the highest physical resolution of all the sensors at 147 lp/mm. Unless the v1 system has unbelievable optics in the lenses, I'm a bit skeptical that any lens for that system can actually resolve that much detail except maybe at f/2.8 or f/3.5, and you would have to have some SERIOUS aberration control. I haven't seen any MTF charts for v1 lenses, so I really cant say anything definitively there...but I am indeed skeptical. The same would pretty much go for the Sony 24mm APS-C Exmor at 128 lp/mm...I haven't seen anything in any MTF charts that would indicate Sony/Minolta lenses are approaching perfection at f/3.5 or wider by any means, so I'm assuming that sensor thoroughly outresolves any lens you might throw at it.

The Pentax 645D is an intriguing control case, as it partially demonstrates why medium format sensors are capable of resolving such clean, noise-free detail despite their large image size. They have rather large pixels, spread over a very large sensor area. Its about the same density as the Hassy H4D-60, which is more of a true "full-frame" digital medium format camera at 54x40mm.


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## dhofmann (Jun 4, 2012)

jrista said:


> If we assume a perfect lens, at f/2.8 and 50% contrast, you can resolve about 247 lp/mm...



How do you determine that number? The common formula of "1600/f-stop = lp/mm" means a perfect lens at f/2.8 would resolve about 571 lp/mm, over twice your figure of 247 lp/mm.


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## RLPhoto (Jun 4, 2012)

Meh, Don't stress over resolving power and sensors too much. It usually works out fine when you do a good job getting correct settings.

I took the 7D which has one of the most demanding sensors from its lenses and shot with an old 1970's Cosina 200mm F/4 adapted from pentax K mount. It had horrid color and was optimized for B&W shooting. I took a couple of really nice sharp photos with it.


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## jrista (Jun 4, 2012)

dhofmann said:


> jrista said:
> 
> 
> > If we assume a perfect lens, at f/2.8 and 50% contrast, you can resolve about 247 lp/mm...
> ...



I am basing my numbers on an MTF of 50% (hence the "at f/2.8 _and 50% contrast_"). I believe the 1600/f-stop is based on rayleigh, or an MTF of 9%. MTF 50% is commonly used with photography, where as Rayleigh/MTF 9% is usually used in reference to human visual acuity (and then, usually referring to our ability to barely resolve two closely spaced points of dim light on a black background...i.e. stars). I prefer MTF 50%, as that relates better to the clear, sharply defined kind of detail people prefer in their photography, where as MTF 9% might apply assuming you were ok with detail of extremely low contrast (i.e. barely discernible differences.) To be exact, MTF at 9% is about 532 lp/mm, so the 1600/f-stop is *really* pushing it for cameras. 

Once you get to that level, or when you start talking about MTF 0% (which technically is just barely above 0%), there are only a few cases where such low contrast is applicable. The most notable being the detection of binary stars from a what otherwise resolves as a single point-light source in astronomy & astrophotography...at just above MTF 0% you can detect whether a resolved point in a photograph represents a single star or a binary (or even ternary) star based on how the diffraction pattern presents. 

Currently, there isn't a _commercial-grade_ camera that can even come close to resolving that much detail, it usually requires high resolution, scientific-grade cooled CCD's and appropriate detection software. You can also use superresolution techniques with commercial-grade gear to produce images that can then be processed to identify binary stars at MTF 0%, which is something the amateur binary star discoverer can do these days if they wish, although its not as effective (superresolution is still a newer technique, and its not guaranteed to leave the presentation of a multi-star airy disc in tact in all cases.) The best consumer-grade sensors on the planet are barely capable of 130lp/mm, and when you factor in the nature of multi-component optical systems, the actual final spatial resolution of a whole camera system tends to be quite a bit lower than that of the highest resolution component (be it lens, sensor, whatever.) So...MTF 50%...in my opinion, it is more realistic for real-world photographers.



As a side note, modern *lenses* are not restricted to projecting light at any given contrast level. _Measurements of resolution_, in the form of MTF, determine spatial resolution at a given contrast level...the contrast level is a factor of the measurement, but it is not a limitation of the lens itself. As such, there is nothing to prevent a LENS from projecting an image at any contrast level...0% to 100%. It is entirely possible to project an extremely fine white line on a black background that is 1/(571*2)mm thick (0.000876mm) with a lens. The contrast of that line could be extremely low (so blurred that it barely registers more than pure black)...even below the level at which the human eye can detect (which would be 9% contrast), and well below the level at which the best modern DSLR or even medium format sensors could resolve in any meaningful sense.

There are some films that are capable of resolving far more than the best sensors today, such as a Zeiss film capable of resolving about 400lp/mm at ISO 25 (which, as far as I know, was only ever used for the purposes of testing a (possibly..it may still exist) short-lived and somewhat legendary...in certain circles...400lp/mm ultra fast lens.) It should be noted, however, that the nature of film and a very meticulous and expensive manufacturing process makes it a bit easier to support such incredible spatial resolutions (which would only be possible at very wide apertures, or at barely discernible contrast levels and narrower apertures). Most digital sensors follow a bayer array design, and usually have low-pass filters in front of the sensor. That puts a hard limit on the amount of resolution you can achieve digitally. Canon has claimed their newer L-series lenses (not exactly sure what "newer" means...from the time I read that, it was around 2008 or 2009, so perhaps within a few years of that date) are capable of resolving 45mp worth of full-frame CMOS sensor resolution...which pipes in at arounb 113-116lp/mm (f/5.6 or wider, as any narrower than that and diffraction limits your resolution.) A sensor might barely be able to resolve a


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## Dark Mark (Sep 17, 2014)

To add a historical note, I remember the photo magazines of the '70's and 80's publishing test resolution of lenses, usually in lp/mm. Most normal lenses considered as excellent had a center resolution of 90 - 100 but fell off dramatically towards the edges, the better lenses, macro, and Leica lenses usually reported a resolution spec of about 80-90 lp/mm but uniform from edge to edge. I have used my old Leica and Nikon lenses with the EOS M (18 mp APS-C sensor) with excellent results (oh, but much slower work, no autofocus). The old Nikon 55mm macro and the Leica Sumicron-C were truly perfect from edge to edge with the EOS M compared to the small errors seen in the magnified image with the two EF-M lenses. The 4 Canon lenses I use have shown better overall resolving power by a combination of more modern optics and image stabilization (telephoto moon shots, macro bug and flower shots). Based on the simple sensor size explanations of "jrista" a 40+ mp full frame sensor is needed to match the resolving power of the 18 mp APS-c and will not be outperformed by those old lenses but just could be by Canon's modern lenses. At least one would hope so before Canon introduces a 40-50 mp FF sensor


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## Aglet (Sep 17, 2014)

*Re: Lens 'resolving power' vs sensors - what's fine these days*

@ JRista

Just updating a couple of your sensor rez data examples.

*Present MFT is over 16MP.*
E.g. OMD EM10, 4640x3472 in 17.3x13.0mm sensor = 134.1 lp/mm
The more I use this camera, the more I'm impressed with it! I can only imagine a FF with pixels like this. (~9650x6450)


A very good lens for the moment is the 75/1.8






that's at 60 and 20 lp/mm

or the Sigma 60mm Art for $210, fantastic, not even considering the price!







*Nikon 1 v3/j4 is over 18MP*
5248x3502 in 13.2x8.8mm sensor = 198.8 lp/mm

There's some very good glass available, one of them's the cheap 30-110mm kit lens, under $300. (80-270mm FF equiv)
MTF below:











and their 10-30 kit lens:












Oh, ya, and the *Pentax Q7* is a mere 
4000 x 3000 on a 7.4 x 5.6mm sensor = ~270 lp/mm
I've got one of these things too; can't say I've got a lens that can keep up to it tho, altho the 8.5mm f/1.8 prime is decent.
The only thing reducing the quality of the images from these little camera systems is the per-pixel noise as their full-well counts are so low that shot noise is an issue much sooner than with larger sensors.

Edit: tired fingers and brain. at least one type fixed


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## ChristopherMarkPerez (Sep 17, 2014)

Once you agree on what "resolution" means, there are a number of answers which can be verified in the real world.

There is the ability of a lens to render light to dark transitions "accurately." Independent of how well contrast is rendered, you can have a very very sharp optic. You often see this in tessar-formula, artar-formula, and planar-formula lenses from the time before optical coatings.

There is the ability of a lens to come as close as possible to matching the physical theoretic limits of diffraction. Commercial available lenses used at f-stops between wide open and f/11 have diffraction limits (theoretic and practical) that are so far beyond a sensor's ability to capture that kind of resolution you don't need to worry about a thing.

These two way of looking at what I call pure resolution. The human mind, however, "processes" more information than just physical resolution. To a point, the human mind also interprets contrast as "sharpness."

This is why you have MTF charts. They attempt to share how much contrast is passed through a lens. Looking at manufacturing and various "test" websites data can be very confusing, as important details are many times left out. You may be left wondering what you do with the data once you've seen it.

There are, minimally, three other optical effects which will impact the interpretation of "sharpness" by a viewer. These are coma, chromatic aberrations, and field curvature. Broadly speaking, coma takes a point of light and distorts it. Chromatic aberrations take light to dark transitions and adds different colors to a scene, depending on which edge you're looking at (toward or away from the optical center). Field curvature defines what portions of a scene are actually rendered in focus.

Coming back to the human mind and the way it interprets "sharpness", we need to consider how large an image is being viewed and at what distance. We also need to consider how old the viewer is. The older the viewer, the less stringent the "sharpness" criteria.

_Why all this build up to providing a simple answer? It's to, again, recognize that definitions are important. Precisely what are we to consider?_ Which leads me back to your question.

In terms of pure optical resolution (ignoring all other lens effects, unless you buy me a few beers and we have a few hours to consider the topic), and considering APS-C, Full Frame, or Medium Format sensors (an important point here), the sensor is the limiting factor to resolution when using a lens wide open down through f/11 (or for lower density sensors f/16). Further, using jrista's sensor resolution calculations you can see what your sensor is capable of.

That's it. It's that simple. You can sleep well and call it "good to go." The "sharpness" of a lens simply does not matter.

Ah, you say. But the devil is in the details, right? Yes and no. 

A couple things to remember: 
1) Camera manufacturers and stores are in the business of selling you things. If they can get you thinking you need a "better" lens to shoot whatever new sensor is on offer, they get money and you feel safe, even as your wallet is significantly lighter. 

Looked at differently, humans have been making sharp lenses for hundreds of years. The ability to design, grind, align, and build great optics has been with us a very long time. All the little details have been worked out. 

It's come down to design for manufacturability, the all up Bill of Materials, and Gross Margin targets. That's where the trade-offs are made. Which is why when you "test" a cheap kit lens by shooting a brick wall you might be disappointed with the results when shooting wide open (for instance). Yet when shot at f/5.6 or f/8 you probably can't tell the difference between the cheap kit and the hugely expensive L-glass output (I certainly can't and I've looked at this stuff for decades).

2) If you believe that the 1/r formula brings the lens back into the resolution equation, then explain why, in physical (as in science) real world testing (as in the things we can engage in directly) using a Canon 7D that resolves 116lpmm you see 116lpmm resolution as measured using a USAF Resolution Test Chart. For 1/r to "work", wouldn't you get a much lower resolution number?

Further, how is it that I have a USAF spec'd 75mm f/5.6 Biogon design lens that is, in fact, diffraction limited from wide open? Three different companies made these and they were quite common in army surplus stores back in the day. The optic covers 5x5 inches. That's right, inches.

Tested six ways to Sunday using a wide variety of silver based films, including high contrast 1000lpmm technical films the results are the same? It's either the resolution of the film or it's the diffraction limits of the lens (if the film can handle it). It's never been, is not now, and never will be explained using 1/r.


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## AlanF (Sep 17, 2014)

The theoretical resolution of the 12.1 mp 1/2.3" sensor of the SX50 is 323 lp/mm (1.54 µ pixels).
The theoretical resolution of the 16.1 mp 1/2.3" sensor of the SX60 is 371 lp/mm (1.34 µ pixels).

But, the Airy disk diameter for f/6.5, the widest aperture at telephoto lengths, is 8.7 µ, and the SX50 becomes diffraction limited at f/2.5 and the SX60 at f/2.2. The system is mainly diffraction limited, not sensor limited

In other words, there is no real gain in resolution using the 16.1 mp sensor and it will be noisier!


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## jrista (Sep 17, 2014)

ChristopherMarkPerez said:


> There is the ability of a lens to come as close as possible to matching the physical theoretic limits of diffraction. Commercial available lenses used at f-stops between wide open and f/11 have diffraction limits (theoretic and practical) that are so far beyond a sensor's ability to capture that kind of resolution you don't need to worry about a thing.



It isn't as simple as that. Resolving power is always measured relative to a contrast level. Historically, MTF50, or the transfer function at a contrast level of 50%, has historically been used to measure the resolving power of lenses, sensors, and systems. You can measure at contrast levels below 50%, however the closer you get to Rayleigh (MTF9), the more difficult it becomes to differentiate real detail from noise. Additionally, at lower contrast levels, it is generally implicit that the "edge detection" of whatever is doing the resolving is lower...the loss of contrast comes from softer edges. 

Now, even at the rayleigh limit, at f/11, your resolving power is 135lp/mm. We have sensors today that are capable of resolving more than that. Just scroll up a couple of posts to Alan and my own lists of sensor resolutions (in luminance...color resolution would be lower, but luminance is really where detail comes from.) Sensors are only going to be getting more and more dense with smaller and smaller pixels. Across the board, in a few years, there will probably be few sensors out there that couldn't resolve 135lp/mm. 

You also have to remember, output resolution is relative to the RMS of the input resolutions. If you have a sensor capable of resolving 135lp/mm, you couldn't actually produce 135lp/mm resolution in an image when using a diffraction limited lens at f/11. The most you could resolve with such a system is 95lp/mm (at MTF9, which is a VERY low contrast level...possibly below the noise limit of the camera, meaning you wouldn't be able to accurately resolve detail at that contrast level with the exception of a very few special scientific use cases (i.e. ultra high magnification star diffraction spot analysis).) To actually get the most out of that 135lp/mm sensor, you would need a lens capable of resolving a LOT more...which means you would have to have a lens that is diffraction limited, at MTF9, at f/8 (227lp/mm) to get 116lp/mm, and at f/4 (455lp/mm) to get 129lp/mm. You would need a truly diffraction limited lens at f/4 MTF9 to resolve even 130lp/mm out of the 135lp/mm the sensor is capable of...you would probably need an f/2 or f/1.8 lens to get that last 5lp/mm...and such a lens would be extremely expensive (were talking Otus-grade or better here.) 

This all assumes that noise levels in the camera don't swamp real detail at a low contrast level of 9%. Something like a D810 or A7s at their lowest ISO levels should have enough dynamic range at midtones and brighter, however as you get down into the lower midtones, shadows and blacks, noise levels are still going to be high enough that it could be difficult to actually differentiate real detail from noise. Once you move up to MTF20 or MTF50, then the resolving power of lenses drops considerably. An f/11 diffraction limited lens is only capable of resolving 63lp/mm at MTF50, where we can easily pick out the microcontrast between pixels, and images look readily and acceptably "detailed and sharp" to our eyes. 

As far as I am concerned, a lens at f/11 is woefully inadequate for anything where I really need detail. That would primarily be landscapes, but I also try to avoid stopping down below about f/9 for my birds and wildlife for the same reasons...I SEE the difference, the loss in detail, in my images when I do. I'd rather use a T/S lens at a much wider aperture for landscapes, where I could stop down to the ideal aperture of the lens (usually somewhere between f/4 and f/5.6) to get maximum resolution, while avoiding the DLA of the sensor. Again, I can see the results in my images when I do that. There is a meaningful difference between f/11 and f/4 through f/8 when it comes to resolution:






I labeled f/8 as the sharpest, as it's sharp through a greater DOF...however compare f/8 and f/4...at f/4 more detail is resolved, and the difference between f/4 and f/11 is visually obvious. 



ChristopherMarkPerez said:


> Tested six ways to Sunday using a wide variety of silver based films, including high contrast 1000lpmm technical films the results are the same? It's either the resolution of the film or it's the diffraction limits of the lens (if the film can handle it). It's never been, is not now, and never will be explained using 1/r.



I do agree that the 1/r equation is probably a bit simplistic and not accounting for all the factors.


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## Mt Spokane Photography (Sep 17, 2014)

sanj said:


> Hello experts.
> I keep hearing that current Canon lenses are not 'good enough' for newer/better sensors. I would really appreciate a lesson on how this works.
> Thx...


 
Who did you hear it from, and how did they take their measurements of the lens MTF? Most of the online lens testers, including DXO test a lens on a camera, and in every case I've seen, the camera sensor has been the limiting factor.

Roger Cicala at Lens Rentals has the capability to test a lens by itself (No camera attached), and has posted a couple of actual lens MTF values for some conditions. A lens like the 24-70 f/2.8 L MK II or the 70-200mm f/2.8 MK II is supurb. Easily capable of handling high MP sensors. The Canon lenses may be slightly better than the Nikon equivalent, but they are both fantastic lenses.

Here is some more reading on the subject. Jrista throws out a lot of terms that you might not understand, this will help understand what they mean, as well as the other factors that are involved in grading a lens.

http://www.cambridgeincolour.com/tutorials/lens-quality-mtf-resolution.htm


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## Marsu42 (Sep 17, 2014)

jrista said:


> Again, I can see the results in my images when I do that. There is a meaningful difference between f/11 and f/4 through f/8 when it comes to resolution



Thanks for the nice demonstration animation! And I agree, diffraction even at "medium" f-stops is visible - that's why do macro focus stacking @f8 even though stopping down would need way less exposures. Plus of course with macro, the bokeh gets worse on small apertures.


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## vulie504 (Sep 17, 2014)

Whoa..... all of this technical talk is confusing me. Let's imagine that canon releases a 36mp full frame dslr, will that render my "less" resolving lenses such as the 35mm 1.4L, 16-35ii and 85mm 1.2L to doo doo? 
I've heard that the 24-70ii and 70-200ii are high resolving lenses and shouldn't have a problem. I wonder what happened on the Nikon side with using the same lenses on the D800 hmmmm.....


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## AlanF (Sep 18, 2014)

vulie504 said:


> Whoa..... all of this technical talk is confusing me. Let's imagine that canon releases a 36mp full frame dslr, will that render my "less" resolving lenses such as the 35mm 1.4L, 16-35ii and 85mm 1.2L to doo doo?
> I've heard that the 24-70ii and 70-200ii are high resolving lenses and shouldn't have a problem. I wonder what happened on the Nikon side with using the same lenses on the D800 hmmmm.....



Course not! But, leaving the lens cap on and putting a pinhole through it wouldn't reap the full benefit of the high megapixel count though.


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## AcutancePhotography (Sep 18, 2014)

jrista said:


> To start, its best to measure resolution in *lp/mm*, or *line pairs per millimeter*. ....



Thank you for taking the time to write your posts in this thread. I wished there were more such posts on this site.


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## jthomson (Sep 18, 2014)

vulie504 said:


> Whoa..... all of this technical talk is confusing me. Let's imagine that canon releases a 36mp full frame dslr, will that render my "less" resolving lenses such as the 35mm 1.4L, 16-35ii and 85mm 1.2L to doo doo?
> I've heard that the 24-70ii and 70-200ii are high resolving lenses and shouldn't have a problem. I wonder what happened on the Nikon side with using the same lenses on the D800 hmmmm.....



http://www.dxomark.com/Reviews/Nikon-AF-S-Nikkor-500mm-and-600mm-f-4G-ED-VR-lens-reviews-legendary-performers-in-the-range/Nikon-AF-S-NIKKOR-500mm-f-4G-ED-VR-fights-off-both-Canon-and-Sony

The "Legendary" Nikon 500mm F4 flops on the D800's 36mp.


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## 3kramd5 (Sep 18, 2014)

jthomson said:


> vulie504 said:
> 
> 
> > Whoa..... all of this technical talk is confusing me. Let's imagine that canon releases a 36mp full frame dslr, will that render my "less" resolving lenses such as the 35mm 1.4L, 16-35ii and 85mm 1.2L to doo doo?
> ...



Heh, so the Canon 500 has equal or better metrics to the Nikkor 500, yet their composite score is the same because... "the excellent dynamic range of the Nikon D800 sensor."

Sure, why not?

And presumably the Sony a99 has dynamic range similar to the D800, so why doesn't the Sony lens, with similar metrics to the Nikkor lens on a higher-than-Canon DR sensor get the best score rather than that lowest?

Again: heh


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## canonvoir (Dec 25, 2014)

I find all of this fascinating, especially since Canon seems to be on the verge of releasing a high MP sensor and possibly a different EF series lens (although that seems really unclear at the moment).

Could someone go through how to read the MTF chart and what things we should be looking for or noticing on these charts? 

Also, how big a part does flange distance play into this? I hear Sony a7r guys getting picky with some lenses because of the shorter flange distance. I think I recall them talking about how this causes problems on ultra wide angle lenses. Is the EF mount with current flange distance on FF setup better because of increased flange distance?


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## sanj (Dec 25, 2014)

Thank you Jrista and the rest. But I must admit this is a steep learning curve for me.


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## ChristopherMarkPerez (Dec 25, 2014)

If you listen to salesman they'll try and scare you into believing you'll _need_ new optics. Be careful. They want the sale and don't care about reality or truth.

I see that plenty of people have provided an explanation of sensor resolution. jrista's sensor resolution list is correct.

From my perspective and many years of looking at USAF Resolution Test Chart results (scroll down to "Resolution in Photography" on the right side of my blog - http://photosketchpad.blogspot.fr/) that APS-C/FullFrame sensors are currently _the _limiting factor to resolution for lenses shot from wide open down thru f/11.

Said succinctly, commercially available optics are more than sufficient to the task when matched to any new Canon Wonder Camera of around 50mpixel.



sanj said:


> Hello experts.
> I keep hearing that current Canon lenses are not 'good enough' for newer/better sensors. I would really appreciate a lesson on how this works.
> Thx...


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## Sabaki (Dec 25, 2014)

Aaaaaaah! New Terminology for everybody to have considerable knowledge about. 

Never seen these terms used until that interview was posted


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## AlanF (Dec 25, 2014)

ChristopherMarkPerez said:


> If you listen to salesman they'll try and scare you into believing you'll _need_ new optics. Be careful. They want the sale and don't care about reality or truth.
> 
> I see that plenty of people have provided an explanation of sensor resolution. jrista's sensor resolution list is correct.
> 
> ...



There are some less sharp lenses that perform tolerably well on full frame (eg the 100-400mm L version 1) but are not nearly as good on crop, whereas some lenses like the very sharp 300mm f/2.8 perform very well on crop. DxO mark quantifies these differences in their measurements, and you can see the degradation in IQ of the softer lenses on the TDP site tests. I have found the same in my own experience. Are you saying that this is all nonsense and that the sharpness of current lenses is of no importance as they are not the limiting factor in resolution?


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## Mitch.Conner (Dec 25, 2014)

jrista said:


> To start, its best to measure resolution in *lp/mm*, or *line pairs per millimeter*. This is a measure of _spatial frequencies_...light/dark oscillations or waveforms that compose a two dimensional image, be that the virtual image projected by a lens, the image recorded by film or a digital sensor, etc. Measurement in line pairs, or a light line paired with a dark line, is essential to measure microcontrast, or the ability to discern the difference between a light line and a dark line that are right next to each other.
> 
> (NOTES: For reference, the human eye is able to discern a line pair when contrast is as low as 9% (this is called _Rayleigh Criterion_). Modern sensors capable of barely resolving detail around the same level, probably closer to 12-15%, however at such levels details can become inconsistent and often "useless". Low-pass filters are usually used to cut off spatial frequencies somewhere below this level to eliminate what effectively becomes additional image noise and possibly moire in the presence of regular repeated patterns. Sensors can only really resolve a line pair as consistently separate light and dark lines when contrast is about 50%. For any imaging medium to resolve a line pair, it must have twice the resolution as the frequency being sampled...so for a sensor to resolve 100 lp/mm, it must have at least 200 rows of pixels per millimeter. This called the _Nyquist Rate_, and the maximum resolution of an image that can be captured...the maximum frequency that can be usefully sampled...is the _Nyquist Limit_.)
> 
> ...



I realize that I'm replying to an old post that's part of an old thread with recent activity due to the high mp alleged confirmation by Canon.

I wanted to address one thing in particular though. I question the assumption that recent lenses and mk ii lenses are being refreshed for higher mp sensors, including current aps-c 18mp crop sensors.

I was wondering earlier how the current EF 70-200mm f/2.8 IS II USM would perform on a higher mp camera, so I tried looking up its resolving power in lp/mm and ran across a review I hadn't read before, by DxOMark stating that for that particular lens its predecessor, the original EF 70-200 f/2.8 IS USM (mk I) had more resolving power. Then in the comments, they stated that it was sharper on aps-c bodies than it is on ff bodies (which I didn't understand). I've not read any other review that made such claims.

Then I decided to look into the new 100-400mm zoom mk II and read that more or less it has about the same resolving power as its predecessor, and the true improvement is in the stabilization upgrade/update. Was it already resolving well enough before? I've never used one, so I don't know.

Any thoughts on this. I am aware that many here are not fans of DxOMark and their results, but the 100-400 II still has me scratching my head.


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## canonvoir (Dec 26, 2014)

Mt Spokane Photography said:


> sanj said:
> 
> 
> > Hello experts.
> ...



I hear this from the Sony fanboys (not to be confused with Sony enthusiasts) and sales people (which I know has been discussed in this thread). I know people are about the latest technology (I am definitely in the category of wanting to get in the Sony pool to get higher MP with a lighter, smaller camera) but if I have heard this once I have heard it a thousand times. Everyone acts like my 50 1.2L, 85 1.2 L, 300 ii 2.8, etc. are relics that couldn't possibly handle a ~50 MP sensor. 

This is why I searched out this topic. I asked myself is this why Sony lenses start at ~$1,000 and go up for slower speeds than I am use to owning? Is this why the don't produce a $500 50mm? I don't know the answers. 

I do know Canon has taken its sweet time with higher MP's.


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## jrista (Dec 26, 2014)

Mitch.Conner said:


> I realize that I'm replying to an old post that's part of an old thread with recent activity due to the high mp alleged confirmation by Canon.
> 
> I wanted to address one thing in particular though. I question the assumption that recent lenses and mk ii lenses are being refreshed for higher mp sensors, including current aps-c 18mp crop sensors.
> 
> ...




Well, your relying on DXO.  Guess that's enough said. ;D 


One thing I will say is, older Canon lenses often resolved very well in the center, and very poorly in the corners. For film, where huge enlargements were not as common (most of the time, it was smaller enlargements or contact prints, so maybe 8x10 tops on average), poorer corners were probably not as much of a problem. Newer Canon lenses and the Mark III TCs have all been addressing corner performance. Some of Canon's newer lenses did not improve center or midframe resolution much...but improved corner resolution a ton. Some lenses, like many of the new Great White Mark II generation, improved resolving power across the board.


For the best lens resolution tests around, check out Roger Cicala's LensRentals blog. He regularly tests new lenses, using an optical test bench (so he's testing LENSES, not camera systems), and his comparisons tend to be more accurate and generic than most. None of this "limited by the sensor" crap that skews and convolutes results.


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## Don Haines (Dec 26, 2014)

jrista said:


> Mitch.Conner said:
> 
> 
> > I realize that I'm replying to an old post that's part of an old thread with recent activity due to the high mp alleged confirmation by Canon.
> ...


Also Roger tests multiple copies of lenses and his lenses are normal retail lenses. I am always suspicious of lens tests where the manufacturer sends the tester 1 copy of the lens.... odds are that the 1 lens is cherry picked and is not representative of a typical lens....


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## Mitch.Conner (Dec 27, 2014)

Thanks for addressing my question guys.


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## LovePhotography (Jan 5, 2015)

JRISTA, I would just like to say, "THANK YOU" for posting this enlightening info, (and even doing so without a grandiose, self-absorbed ego, I might add). You obviously have a serious optical engineering fund of information. Aside from thanking you, I am posting here so I might be able to search this post again and read it a few more times. Again, thanks!


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## jrista (Jan 5, 2015)

Happy to help.  It's just a hobby, really...well, a hobby that assists me in my other hobby, really.  I like to know everything about what I do, so as a photographer, well, I had to know how sensors and lenses worked. So I researched it.


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## Plainsman (Jan 5, 2015)

LovePhotography said:


> JRISTA, I would just like to say, "THANK YOU" for posting this enlightening info, (and even doing so without a grandiose, self-absorbed ego, I might add). You obviously have a serious optical engineering fund of information. Aside from thanking you, I am posting here so I might be able to search this post again and read it a few more times. Again, thanks!



I would also like to add my appreciation to jrista for his posts which always include "numbers" in his explanations as well as worked examples.

To many bluffers on this site who have read a book or so and think they are experts on very technical matters.


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## gsealy (Jan 5, 2015)

Thanks to all who contributed on this thread. From time to time I have had these same questions, but I never had time to do the research. Excellent discussion.


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## GMCPhotographics (Jan 5, 2015)

jrista said:


> Mitch.Conner said:
> 
> 
> > I realize that I'm replying to an old post that's part of an old thread with recent activity due to the high mp alleged confirmation by Canon.
> ...



There's a few other factors to consider here. Most f2.8 zooms are tested in the middle of their zoom range. The mkII's are optimised at their previously weakest point...at the long end or the wide end, depending on which lens. The 70-200 f2.8 LIS II is a lot sharper at 200mm f2.8 then the mkI. But it's slightly softer at 70mm. Stop down to f8 and both lenses are just as sharp as each other. There is little difference. 
The 24-70L was optimised for the 70mm end, the new one is better at the 24mm end. Again, stop down a few stops and there is little between them. 

On most zoom Lenses, sharpness often changes slightly through the focal range and focus range. Very few test sites take this into account. A lens which is really sharp at one end of the focal range at infinity will have a different sharpness score than one at the other end of the focal range and at Minimum Focus Distance. We are also assuming that every photo is taken on a quality tripod and with perfect focusing.

Photographers often get themselves twisted up over minor sharpness issues, making big purchase decisions over very minor issues. I've been using a 21-22mp sensor since the 5DII (and currently 5DIII) and I've found that it's a really good sensor density for all of my photographic needs. It's an optimum balance between sharpness, resolution, noise, lens resolution burden and file size convenience. I'm really not that fussed about a 40+ mp full frame camera, which is against the tide of a lot of forum thinking.

Photography isn't so much about the kit as it is about a great photograph. Too much attention on the science of photography can pull us away from the the reason we have the kit. Yes the kit helps, the science part...but really it's about the art of the photo not the process or kit. Talk to most great photographers and they rarely talk about kit or technique.


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## jrista (Jan 5, 2015)

I agree that in the end it is mostly about the photograph and the technique. We are all after the holy grail of stunning, beautiful, compelling photography, and that's what we should strive for.


That said, people DO make new purchases as they find the need to expand their kit. You can either be educated, and understand the nuances of optical and sensor resolution and how they work together to affect your final results, and therefor be properly equipped to make the best decision FOR YOU.... Or, you can listen to all the myths and propaganda that permeate the web about resolution (i.e. that the diffraction limit is a hard cutoff, after which smaller pixels behave more poorly than larger pixels...complete and utter TRASH!) and poorly managed black-box "single number" testing (i.e. like DXO), and make the wrong decision based on bad or wrong information.


I believe it is helpful and important to understand how the equipment in your hand works when it comes time to change or upgrade equipment. It may not matter in the field when your out there shooting, and your mind should be focused on all the other aspects. But when the time comes to actually buy a new lens, it's important to know whether you NEED to buy that $4000 Otus....or whether that $1000 Sigma would serve your needs perfectly well. There are some use cases where an Otus is probably the only lens that will give certain photographers the kind of IQ you want, but the Sigma would probably serve most more than well enough...and you should be properly equipped to make that decision with REAL FACTS, rather than myths and misunderstanding.


That's why I take the time to say the same boring things over, and over, and over, and over....and over again.  Because these damnable myths just won't die!


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## epsiloneri (Jan 5, 2015)

GMCPhotographics said:


> Photography isn't so much about the kit as it is about a great photograph. Too much attention on the science of photography can pull us away from the the reason we have the kit. Yes the kit helps, the science part...but really it's about the art of the photo not the process or kit. Talk to most great photographers and they rarely talk about kit or technique.


There is a wide range of great photographers, some pushing the techniques more than others, like e.g. Ansel Adams or Lennart Nilsson. Then there is photography where technique is of dominant importance, like in medical photography or the astrophotography that jrista engages in. Contrast this to e.g. photo journalism, where "f/8 and be there" is the guiding principle. What I want to say is, photographers put emphasis on different things, and there is no "right" or "wrong" amount of attention given to technical details. In general, though, I believe that mastering your tools by knowing their limits is helpful, even in situations where it's not critical. Knowledge is power!


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## Lee Jay (Jan 5, 2015)

jrista said:


> Happy to help.  It's just a hobby, really...well, a hobby that assists me in my other hobby, really.  I like to know everything about what I do, so as a photographer, well, I had to know how sensors and lenses worked. So I researched it.



Just wanted to point out that the lp/mm for each sensor posted way above are only correct if you have monochrome sensors with tiny pixels (low fill factor) without microlenses and without an AA filter. If you have a Bayer sensor with real pixels and an AA filter, you're going to need at least 2.5 and maybe closer to 3 pixels per line pair.


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## jrista (Jan 5, 2015)

Lee Jay said:


> jrista said:
> 
> 
> > Happy to help.  It's just a hobby, really...well, a hobby that assists me in my other hobby, really.  I like to know everything about what I do, so as a photographer, well, I had to know how sensors and lenses worked. So I researched it.
> ...




If you actually read my post, I stated as much.


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## Lee Jay (Jan 5, 2015)

jrista said:


> Lee Jay said:
> 
> 
> > jrista said:
> ...



You made a passing reference to this in a different post and then posted wrong numbers and proceeded to reference those wrong numbers. If you knew this, why not just use more correct numbers?


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## jrista (Jan 6, 2015)

Lee Jay said:


> jrista said:
> 
> 
> > Lee Jay said:
> ...




What wrong numbers? I stated that they assumed a monochrome sensor. Why did I assume monochrome, rather than something else? Because there are a lot of factors that greatly complicate "reality", and I preferred to keep things simple, as not everyone is a mathematician or an engineer. It's easy enough to approximate after the fact to account for other blurring factors. You may care that everything is 100% perfectly exact...most people don't. And when my goal is just to get across *the concept*, absolute exactitude doesn't matter. 


BTW, I did not make a passing reference to the fact that I assumed mono in another post. I made a direct reference in the post I made in this thread:




jrista said:


> Real-world resolution can differ a bit *when you factor in* bayer interpolation, low pass filters, bayer array layout, etc.


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