Technical Discussions

Autofocus Reality Part 3B: Canon Cameras

Published August 1, 2012

Some days it’s good to be a geeky gear-head. This is one of them because a) I finished testing autofocus on all of the Canon camera bodies we had, b) I actually found out some interesting stuff, and c) I got worked up about camera marketers while doing it, so I have my next post in the works already.

Because I’ve been writing this series on the fly (telling you what we found as we found it), I’ll keep going in that fashion and keep the conclusions for the end of the article.

What We’ve Found So Far

In the first Autofocus Reality article, we demonstrated two things:

1. Phase-detection autofocus (even using still targets and center-point only) wasn’t nearly as accurate as contrast detection.

2. The contrast-detection autofocus was about as accurate as the most careful manual focusing.

Part two of the series showed that a few newer lenses did focus as accurately as contrast detection on 5D Mark III cameras but not on 5D Mark II cameras. The third article (part 3A) showed that the newest Canon lenses (40mm f/2.8, 24mm f/2.8 IS, 28mm f/2.8 IS, 70-300mm L IS and 300mm f/2.8 IS II) focus more accurately when mounted to 5D Mark III camera but not on 5D Mark II cameras.

The Canon 70-200 f2.8 IS II, oddly enough, seemed not quite as good as the above lenses, but more accurate than the older ones. Whether this was oddness in my measurements or a real finding, I wasn’t sure.

Since we knew that the newest lenses autofocused accurately on 5DIII but not on 5DII cameras, the next step was obviously to compare an accurate AF lens on different camera bodies to see with which ones it was capable of accuracy.

We expected the 1Dx (which has the same AF system as the 5DIII) would be accurate. We weren’t sure about the others.

Today’s Contestants on The Focus is Right!

We know the Canon 28mm f/2.8 IS II had accurate autofocus on the Canon 5DIII so we chose one copy to be our test lens.

We AF microadjusted each camera to the lens prior to shooting. If the camera did not offer AF microadjustment, we checked the body with the test lens and exchanged it for another copy if the lens back or frontfocused at the test distance.

(Microfocus adjustment makes absolutely no difference in the shot-to-shot variation in AF–it only improves the average value of the group. But I got tired of explaining that to people in the previous articles. It was easier to just do it than to answer another 50 emails.)

We then tested it in our Imatest lab using one copy of each Canon camera we carry. To save you from running amok on the internet, finding out which cameras are how old and have what kind of autofocus, I’ve listed that information in the table below.


Camera Year released Year firmware AF description
1DsIII Dec-07 12/16/09 45 point, 19 cross, 26 assist, f/4 at center, dedicated AF processor
5D II Dec-08 2/28/12 9 point, f/2.8 cross center
50D Dec-08 2/28/12 9 point cross, dual diagonal center cross
7D Aug-09 4/25/11 19 point, all cross, center dual diagonal cross (advanced algorithm), first “zone AF” and “spot AF”
1DIV Dec-09 3/29/12 45 point, 39 cross (f/2.8-f/5.6, f4 at center), first AF expansion camera
60D Aug-10 6/19/12 9 point, f/2.8 cross center
T3i Jan-11 1/30/12 9 point, f/2.8 cross center
1Dx Mar-12 2012 61 point reticular, 41 cross type, 5 dual diagonal cross, including center
5D III Mar-12 2012 61 point reticular, 41 cross type, 5 dual diagonal cross, including center
T4i Apr-12 2012 9 point, f/2.8 dual cross center, hybrid CMOS AF Live View


I suspected that the autofocus improvement we’ve seen had more to do with hardware than firmware, but I listed both year of release and year of latest firmware upgrade for completeness. I also listed the basics of the camera’s AF system, as well as any marketing comments made about it at release like the 7D having “the most advanced AF algorithms.”

My thought going in was the difference would be in hardware not firmware. I don’t think any amount of firmware is going to make the AF sensor on the lower left behave like the one on the lower right, even in center-point, single-shot mode.


The Results

In the lens variation article, we used the standard deviation (SD) to measure how accurately the camera focused: Softer focus results in lower Imatest values. As an example, we’ve put up a graph of Imatest values for the 5D Mk II versus the 5D Mk III below.

 As you can see, the 5D Mk III shots (red square) are all very similar. The 5D Mk II shots (blue diamonds) are more spread out: The variation in shot-to-shot focus is greater.

In this example, the SD of the 5D Mk III samples was 17 lp/ih, while the SD of the 5D Mk II was 38.5. Those are similar to the numbers we’ve seen over and over—accurate focusing combinations have SDs in the teens while less accurate ones have SDs in the 30s.

Rather than clog up the post with a lot more graphs, I’ll list the SDs of the various cameras with the 28mm f/2.8 IS lens in the table below.

Camera SD
1DsIII 29
5D II 38.5
50D 34
7D 41
1DIV 22
60D 34
T3i 41
1Dx 17
5D III 17
T4i 29


It’s a little confusing. There’s a range of variation, of course. But clearly the 5DIII and 1Dx do better than the other cameras, while the 1D Mk IV seems to be a bit between those two and the rest of the pack.

It seems a little clearer to me if we graph the standard deviations and separate the cameras by type (more expensive at the top, less expensive at the bottom.) The oldest cameras in both groups are on the left, while the newest are on the right.


A couple of points are worth making.

The graph of the more expensive cameras seems to show a pretty logical progression. The 1Ds III is by far the oldest, having been around since 2007. But it included every possible AF technology of the day, including a separate AF processing chip. The 5D Mk II, even on its release, was known to have “consumer-grade” autofocus.

Despite my well-recognized modesty, I will also point out that when the 5D Mk III was first released, and Canon fanboys were dropping off cliffs right and left, I said “the 5D III is no minor-upgrade camera; it’s an entirely new camera using the old camera’s name”. Its autofocus system is certainly not a minor upgrade–it’s moved over to the big-boy camera side.

I had hoped the T4i might be more accurate than it was, at least with new lenses. It does seem more accurate than the other consumer / prosumer cameras in phase detection, but it’s not nearly as good as the 1Dx or 5D III.

I assume that it’s new hybrid LiveView system does not carry over to create phase-detection AF. I will say, in it’s defense, that when focusing in LiveView it is obviously faster than and just as accurate as any of the other cameras, including the 5DIII and 1Dx.

So Why Could This Be?

All this autofocus stuff 1) gave me a headache and 2) made me rather curious and uncertain.

I started doing a simple demonstration of what I already knew: Phase-detection AF isn’t as accurate as contrast-detection AF. But then I got results that indicated sometimes it is just as accurate as LiveView. But you have to have a certain camera and a certain lens or it doesn’t happen.

This didn’t make much sense to me.

I would have understood if each generation of newer cameras and lenses got a little better. Or if a new camera or lens was dramatically better. But why a rather sudden change, and why did you need both a new camera and a new lens?

I spent a fair amount of time emailing with Dave Etchells of The Imaging Resource  and who was kind enough to bounce ideas back and forth with me. His thoughts sent me on the right track for figuring this out.

I started off by trying to find out how long it took for an autofocus improvement to go from idea to released-to-the-public. I found one answer in a Canon patent from 2003 describing combined phase / contrast-detection AF in the camera mated to a lens using a stepper motor.

Which we saw  . . .  oh, yeah. Now. With the Canon T4i / EOS-M sensors and new STM motored lenses.

One thing of interest in this patent application, tucked away in the background section, is the following statement:

. . . though the prior art indicates a method for realizing high speed and high precision of autofocusing at the same time, it does not accompany a lens drive control for realizing this and thus does not adequately realize [. . .] high precision of autofocusing.

In other words, back in 2003, Canon recognized that a high-accuracy AF system in the camera required a more accurate lens drive to yield precise autofocus. You can’t have one without the other.

Suddenly the need for both a new camera and a new lens to get accurate autofocus began to make sense. But wait, the patent was talking about using a stepper motor to achieve accurate AF. We did find the 40mm pancake (stepper motor) was more accurate. But we also found that the new 24mm, 28mm f/2.8 IS and 300mm f/2.8 IS II lenses were more accurate. Yet they don’t have stepper motors.

Then I read on a bit further in the patent:

In order to achieve this objective, this invention provides a camera system comprising: a first focus detection unit, a second focus detection unit, a stepping motor that drives a focusing lens, . . . or a rotation detector, which detects the rotation . . . of the motor. . . The control circuit performs closed-loop control, based on the output of the rotation detector to control the motor.

The wording of this patent, back in 2003, suggests that closed-loop was not how AF worked at that time. It was largely open loop. The camera took a measurement and told the lens where it should go. Done.

This is backed up by a lot of other information, including statements in Canon’s “EF Lens Work III” and quotes made by a lot of people who would have known.

It’s clear that later AF systems were closed loop (the camera double checked where the lens had gone), although exactly when and where that change occurred I don’t know. But this probably explains the lengthy, and now largely meaningless, debates about whether systems were open or closed-loop: They used to be open. Now some (probably most) are closed.

More to the point, though, is the comment that a rotation detector would be needed in lenses driven by ultrasonic motors to increase accuracy of the focusing movement.

If this is the case, then the newer Canon lenses should definitely have a rotation detector built into them. We know there are rotation detectors in many lenses released after 2000, but if they are  in older lenses we can’t identify them, so this fits too. (As an aside, I am particularly skilled in finding them because usually if you touch them with your fingers the lens won’t focus anymore and the unit has to be replaced.)


From Left: A Canon and Nikon magnetic rotation detector.


Just to be certain, I asked Aaron to find an excuse to take apart one of the new lenses. Or failing that, I told Aaron to take one apart and not tell Tyler or Drew, who never really believe we can put them back together correctly.

The result: Aaron checked and the newer lenses did have rotation detectors.

There was one other big hint hiding in plain sight in Canon’s resource article on precision cross-type AF sensors. The article states that the farther apart each pair of AF sensors are (each pair compares phase from opposite sides of the lens) the more accurate the sensor. It also states only the 5D Mk III and 1Dx have them. I italicized some of the quote for emphasis:

[…]simply by reading which pixels on each sensor line are being struck by light, the AF system can tell instantly what direction to move the lens in for proper focus, and by how much to move it. . . Canon EOS SLRs with high-precision AF sensors simply move the pairs of sensors much farther apart, and accordingly, the AF information can be more finely broken-down and reacted to.

The 5DIII and 1DX have f/5.6 cross-type sensors (most previous cross-type required f/2.8 or faster lenses). The central AF sensors in these cameras also have diagonal cross sensors. The article continues:

For pros who prefer to use the center AF point, simply manually selecting it [. . . ] gives the user the highest precision AF possible with these cameras (assuming an f/2.8 or faster lens is being used). And, with their unique diagonal cross-type layout, the AF points are much more likely to latch-on to typical horizontal or vertical subject details.

In Summary

As it turns out, my little tests just confirm things that were already published (if obscurely.)

The two newest Canon cameras have more accurate phase-detection sensors than their previous cameras. The newest lenses have more accurate focus movement (or provide more accurate focus movement feedback, or both) that takes advantage of those sensors.

Older cameras don’t have accurate enough AF sensors to take advantage of the new lenses’ capabilities.  Older lenses can’t move their focusing elements with enough accuracy to take advantage of the new cameras’ accurate sensors.

It’s rather sad (given the amount of other work that’s piled up during this little series) that I didn’t find this information until after I’d done all this testing, but it’s rather a testament to our times. There’s so much marketing drivel and useless verbiage thrown about that the marketing noise drowns out the actual useful information the camera makers offer us.

But that’s the topic of another blog post in which I will take personal offense at the marketing crap that’s been shoveled our way at an ever-increasing rate.

I don’t believe we photographers are nearly as stupid as the marketers seem to think we are. In the meantime, while I’m on this rant, I highly recommend Thom Hogan’s very funny look at camera icons “A Different Kind of Focus.” Thom writes better stuff sitting on the tarmac waiting for takeoff than I do at my desk.

And I guess, given all the marketing fluff, I wouldn’t have really believed “better autofocus” if I hadn’t seen it with my own tests.

I’ve heard it before and it wasn’t so. Not to mention I doubt seriously we’d have seen the marketers say, “better autofocus…but not with the lenses you already have.” So maybe this is worthwhile after all.

Otherwise I might have put my trusty old 85mm f/1.8 on a 5D III and thought “not better at all, they’re lying to me again.”


Roger Cicala (with thanks to Aaron Closz and Dave Etchells)

August 2012

Author: Roger Cicala

I’m Roger and I am the founder of Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Technical Discussions
  • Roger Cicala

    Richard that’s a good suggestion. I’ll see about working that in next time.

  • Peter

    This has been a brilliant series of tests. Thank you so much guys. Can I blame you guys when my wife asks what on earth inspired the lens renewal program I will now have to start to get the best out of my 1D X?

  • I’d love to see you include a 1Ds MkII in the mix. I suspect the result would be surprising.

  • Excellent articles, thank you. I’ve noticed a considerable improvement with my 5DIII and 70-300L combination. My walkaround lens is the 24-105, and it seems to behave better on the 5DIII than it did on the 5DII, but the improvement isn’t as dramatic. As the 24-105 is almost seven years old now, perhaps it’s time for an update with better AF?

  • Very nice and informative articles, thanks!

    Hello Tern,

    you asked:

    “It’d be interesting to see if the theoretical choice of ‘accuracy (if you have f2.8)’ (Canon) vs ‘availability (cross point with any lens)’ (Nikon/Pentax) actually matches to reality.”

    Matt and Jamieson, two “international award winning Toronto Wedding Photographers”, made a little test.
    It wasn’t such an extensive testing, like with SD outputs and selection of the better performing cameras and lenses of a stack (just two cameras), but at least for me it yielded surprising and kind of diverse results, like the one on this site.

    Greetings from Germany

  • Good point, Markus. The 7D was a test bed for so many focus technologies, perhaps now what Canon has learned can be applied retroactively.

  • Hello Roger, thank you very much for your article. I find it very useful and your findings are very close to my experience with Canon 7D.

    Personally, I do not like AF of 7D. Yes, I got used to it, I use 7D professionally and make money with it, but too many odd OOF images for my taste. As you found out, the SD of 7D is great (not that good).

    But the biggest disappointment for me was a 7D + Canon 100mm L macro IS combo. I thought with a newly built and quality L lens with a f2.8 aperture AF would be dead on every time. I was wrong. My 7D and 100mm can miss some obvious and “easy” situations with good contrast. The focus variation is large – sometimes it’s dead on, sometimes it’s close, sometimes it’s off by a mile. And microadjustment doesn’t help.
    Don’t get me wrong, I do get usable and extremely sharp images with this combo but I expected more precise AF, especially on f2.8.

    The best results I get when I press AF-ON button several times before taking the image with very shallow DOF. It’s slightly more precise than using af-servo. And you can clearly see how camera shifts the focus, even though both times the camera gave green light for AF.

    So, I cannot wait buy MK3. Thanks again for your article!

  • Markus

    It’l be interesting to see if the coming major FW ugrade for the 7D will make a difference.
    Roger, do you have any idea on the accuracy of the 7D’s AF sensors (at least, it also reads “center dual diagonal cross”)?

    btw: Great article – it’s really sooooo difficult to separate marketing hypes from real advances. And most of us simply don’t have the possibilities for these checks.

  • Very interesting. Since it is such an outlier (both in expectation and in contradictory results) I would almost want to try some other tests on the EOS 7D to see just what it is actually good at (or which lenses it is good with), since it obviously isn’t center point with the lens you were using.

  • Peter

    So, should I now feel a little less bereaved that I sold the following to help pay for my mk III?

    17-40 f4
    135 f2

  • Richard Cowan

    Very interesting comparison, I wonder how other systems are going to perform.

    Can I make a suggestion however. Presenting SD values like this, particually when comparing different bodies of different resolutions and AA strength is a little confusing.

    Can I suggest that you first normalize all the tested MTFs to the average MTF for that camera, lens and AF method. Then we can make more direct comparisons between 21 MPix and 15 Mpix (for example) bodies, without worrying about the effect of different resolutions.

  • Roger Cicala


    In the second article we tried double click and never found it to help. In the third we listed the lenses better with the 5D III, it was only a few of the newest ones, most of the ones that give distance data were not more accurate.

  • Roger Cicala


    The manual focus were all using 10X Live view. I’m not very accurate through the viewfinder, although I’m a lot better with a focusing screen. I don’t think I’d be as accurate as with Live View even with a screen, but I could be wrong. And my eyes are old, others would be better than me.

  • Roger Cicala

    Zak, I don’t know if they are worse (maybe, or more likely some but not others). I can’t think of any way they’ll be better.


  • Roger Cicala

    Ethan, I think waiting is silly. We’ve all been getting by pretty well with what we’ve had. Not to mention these are lab tests – the real world doesn’t have a test target on it, and things aren’t as neat and clean as the lab was. My ‘keeper rate’ is about 80% out in the real world. Maybe with this new equipment it will be 90% or maybe 82%. I wouldn’t drop good lenses over it.


  • Roger Cicala

    Hi Jim,

    I don’t have any information about mirror less versus SLR – I think all we’ve shown is for still subjects contrast detection is more accurate with a few exceptions on Canon cameras. I would guess that using Live View AF on an SLR would be as accurate as using a mirrorless. But we’ll find out in a couple of weeks.


  • This is a really interesting article. The 5DII’s autofocusing really is hard work so it’s great to read that the 5DIII has that sorted. I’ve noticed a few quirks too. Comparing our 600D “go anywhere” camera to one of our 5DIIs sometimes the 600D is better. Looking at the graphs it looks like there’s actually not much difference between the two!

  • rf-design

    Technical PDAF is a closed-loop system because in the end the system decide AF is ready. The focus motor have a mass to accelerate, have slip, limited resolution to control forces and finally limited precision. If the system works with a limited number of optical measurement control samples the final step before AF confirmation could be without optical measurement. That could be defined as some manner of open-loop.

    What possible blame the hole combination of marketing and product definition is that there is a possible tradeoff of PDAF speed versus accuracy. That seems very natural and is simply different parameters in the driving SW to control the motor more slowly but to have more accurate focus. That is simply nonexistant in any PDAF camera and shows the ignorance of the product defintion against the user. I anticipate that the lens protocol should be backward compatible but system cameras should be run optimum with an existing system and not enforce technical unnecessary system component replacements.

    The best possible motors are moving coils which fit better in nonsystem cameras but there the CDAF is the possible limiter.

  • Anders

    There are several different AF sensor types used in Canon’s cameras.

    The most basic is the short base line, single line sensor type. They are used in all peripheral points in the older cameras, and in some in the newer ones too. Due to the short distance between them, they aren’t too accurate, but on the other hand can focus at f/5.6. Sometimes they are made so short, thus inaccurate, that they even can focus at f/8.

    Then there’s the long single line sensor. Due to the longer baseline, it gives higher accuracy, but on the other hand usually requires lenses with at least f/2.8.

    There are also dual line, zig-zag type sensors. To increase resolution of the AF sensors, it’s favorable to have more pixels/mm, but smaller pixels gives more image noise in the sensor. By using two normal resolution sensors side by side, one shifted half a pixel to the other, and then combining the read-out, you can get both higher resolution and good signal to noise ratio.
    The dual line sensor can have the same baseline as a single one, so this can offer focus at f/5.6, but still with better precision than the most basic type, although not as good as the high precision sensor, which has its two elements further apart.

    Older cameras offering high precision focus, at f/2.8, typically achieved this only with their center point. The 1D Mark III is one example. However, that camera had high precison in one direction only. The other direction used the standard precision type, at f/5.6. Hence when testing focus with such a sensor it makes a big difference if the test object has a vertical or horizontal line.

    The 40D was the first Canon camera to have high precision, at f/2.8, cross type sensor in the center. That’s the diagonal type of sensor which we also can see in the 1DX and 5D Mark III.

    A camera like the 7D has short base line single type cross sensors in all positions except center, top and bottom.
    The top, center and bottom have sig-zag short base line sensors in cross arrangement. Thus a bit better precison and better ability to detect large de-focus than the standard sensors.
    The center sensor is also augmented by the diagonal high-precision cross type sensor, which requires f/2.8 to work.

    To detail this for every single Canon camera is of course outside the scope of this comment, but it should be sufficient to see that exactly how you arrange the test target is very important for some of the camera models. In real world examples, a lot of other things influence the result too.

  • dominique

    Thank you so much for bringing us that information, Roger! I share your point of view that most photographers would be educated enough to bear more true and useful information about a new camera than all that marketing blabber that even seems to ever become worse.

    What marketing people are trying to hide, others have to unveil afterwards – what a waste of time 🙂

  • Chris P

    Brilliant, easily understood explanation. I have now bookmarked your site and am looking forward to the report on the Nikon system.

  • Jim

    Thanks for this VERY informative article. I am just an entry level DSLR user with an entry level model and consumer zooms. As your test shows, my shots shows quite a bit of sharpness variation. Given the apparent huge phase AF inconsistency, and for amateurs like myself, should we just go to mirrorless and get that fast reliable CDAF? Will I will a significant change in hit rate?

  • About 7D’s AF results against 7D’s AF common feeling :

    Of course, your articles are just part of the story :
    AF absolute accuracy (what you speak about here) is different than AF capacity to acquire and keep focus on a moving subject, where the 7D is percieved as (and probably is) much better than 5DII.

  • Well done !
    I like your scientific mind ! Experimentation, intuition and theory… Great !

    Now several thoughts about it
    1. I guess you realize everybody is now expecting you to list all lenses that actually focus better with 5DIII and 1DX ?

    2. Isn’t that the same list than the list of lenses where EXIF data for distance is available ? (= lenses compatible with E-TTL II flash metering, which make use of distance).
    I know 50mm 1.4 and 24mm 2.8 doesn’t provide the distance but 85mm 1.8 does… as does 70-200 2.8L IS (I). So your answer will probably be “no”.

    3. If I understand you correctly, your results mean that the focus will actually be better on 1DX and 5DIII with lenses without feedback if you double click. Am I right ? Could you test it ?

  • Armis

    Well, I thouroughly enjoyed this series of articles. Some things are actually counter-intuitive: in those tests, the 7D’s AF I’ve heard so many people gush about doesn’t seem to out-perform the 5D2’s old, consumer-grade AF (though I understand the 7D’s AF strengths are in tracking subjects in motion, so the test may not be fully representative); in addition, my 5D2 focuses way better with my 70-200 f/4 IS (where it can’t use the center cross type) than with my 50 f/1.4. Weird.

  • Barnett

    Roger, you are confusing closed loop AF with closed loop motor control. There is a HUGE difference between the two. Let me try to explain.

    Consider an electric motor driving the lens focus position. When you apply power to this motor it starts running at a speed that is difficult to predict. So after some period of time you would have no idea how far the motor has moved. So you need some form of sensor to tell you (ie measure) the current position of the lens. Using this feedback sensor you can adjust the power of the motor (faster/slower/forwards/backwards) to accurately position the lens where you want it. This is called closed loop motor control.

    A stepper motor on the other hand works differently. It has discrete “steps”. The size of these steps are known and fixed. So if you want the motor to move 10mm, and you know each step is 1mm, you tell the motor to take 10 steps, and it will take 10 steps, and you know exactly how far it moved. This is open loop because you don’t need to measure.

    There are various advantages and disadvantages to these two types of motors. One advantage of the stepper motor is that it is a much simpler open loop system. One disadvantage is that you cannot position it in fractions of a step, so the accuracy is always limited to the step size. There are some other advantages/disadvantages too, but I won’t do into that now.

    The point I am trying to make is that the patent you mentioned simply listed these two types of motor control. It has NOTHING to do with the AF control loop which has to be closed loop. Always.

  • Roger,
    thank you so much for this fantastic write-up! I am particularly intrigued by the results for the 7D, which appears to be something of a black horse in Canon’s line-up: it uses an AF system that was something of a departure for Canon at the time (and supposedly designed to be best the ‘consumer-grade’ AF they had just put into the 5D II), but in your testing its (first-generation) ‘improved’ AF system seems to be neither here nor there. As you are probably aware, Canon is set to release a major firmware upgrade for the 7D this month that is not only supposed to improve the camera’s performance in various ways (making it faster in some circumstances for example), but also (a rarity, at least for Canon) adds features that were inherent in the hardware (such as audio levels) but that Canon decided to reveal, dare I say Magic-Lantern-style, only now.

    Now here’s the rub: If I read your assumptions about open-loop and closed-loop AF correctly, it would seem that changing AF performance from one to the other could well be achieved with a firmware update, at least with a camera body whose processors are fast enough pull off such a feat. Said firmware update would allow the camera to
    1) recognize the ability of the new-generation lenses to provide the position of the USM motor with its rotation detector and
    2) if such a lens is detected, change the camera’s AF system so as to provide a ‘closed-loop’ measurement: AF – send data to lens – read rotation data back – AF again – send data to lens etc.

    At least at first glance, a firmware update should suffice to add that capability to the camera – provided that Canon wants to provide that feature to the users of a specific camera model in their line-up and that the camera is in fact fast enough to deal with the back and forth.

    It might be worth checking your results with the 7D once that big firmware upgrade has landed—what do you think?

  • Dave Coombes

    Great article. I have been confused about what Canon has been doing with their releases over the last few years but this makes some quite dull products like the 28mm 2.8 seem much more interesting.

    I do wonder whether third party manufacture will be able to use this at all and whether they even know Canon have been doing this.

    Cheers, Dave.

  • Nqina Dlamini

    You’ve put in a bit of a pickle, I was ready to pull the trigger on a 7D.
    From what I can deduce, I can either save up for a used 1D MKIV or go the 5D III route.
    Thanks for this.

  • mantra

    thanks for this very interesting article, rally an excellent investigation!
    i shoot canon but may i ask a question?
    did you compare the canon and nikon Phase-detection autofocus?
    thanks a lot!

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