Lenses and Optics

Just The Lenses: Canon vs Nikon Zooms at 70mm

Published September 2, 2014

It’s impossible to accurately compare lenses from different mounts using any form of Computerized Target Analysis testing (methods like DxO or Imatest). Target analysis tests an entire system (camera and lens). People try to, of course, but it’s not accurate since you always have the added variables of camera sensor, microlenses, in-camera image processing, etc. Some people try to use adapters to test different lenses on the same camera, but then you have added variables from the adapter and sometimes from sensor stack thickness.

In general, it doesn’t really matter. If you shoot Nikon you aren’t really interested in Canon lenses, and vice-versa. Still, directly comparing the lenses without any camera involved is interesting to some people, I think. Some people are thinking of changing brands – they know the other brand’s camera has higher resolution, but aren’t sure if the other brand’s lenses are as good. More people than ever are shooting lenses across brands using adapters, and they’re sometimes curious, too.

It is, of course, possible that nobody but me is interested in direct cross-brand lens comparisons. But since I am interested and since I have to test all of the lenses in our inventory anyway, I thought I’d show some of that data. If others find it interesting, too, I’ll write up some more comparisons like this.

I chose these specific lenses because I get asked every so often whether a 24-70 f/2.8 lenses at 70mm is sharper than the 70-200 f/2.8 lenses at 70mm. This again is a bit of a moot point, since there’s actually a focal length difference (the 24-70s are about 67mm when the lens says 70, while the 70-200 lenses are closer to 73mm).

But hey, I usually find the opportunity to do a meaningless test hard to resist.

Today’s Contestants

We tested 7 copies each of the Canon 24-70 f/2.8 Mk II, Canon 70-200 f/2.8 IS II, Nikon 24-70 f/2.8G AF-S, and Nikon 70-200 f/2.8G AF-S VR II lenses on our Trioptics Imagemaster optical bench. All copies had been through our routine optical and Imatest screening and passed with flying colors. These are all pretty modern designs (the Nikon 24-70 is the oldest, released in 2007) and I don’t think we’ll be seeing a replacement for any of them any time soon. All were tested at their 70mm settings according to the zoom ring, at f/2.8, and at infinity focus setting. (The actual focal lengths were about 67mm for both the 24-70 lenses, 73mm for both of the 70-200 lenses.)

MTF Charts

One thing about looking at MTF charts that people either lover or hate is that it gives a lot more data than just Imatest resolution numbers. It’s so easy to look at Imatest numbers and say, “A is 875 and B is 820, so A is better.” MTF charts give you a lot more information. That generally makes the summary a little more complex, which some people hate. But it also makes the summary a lot more useful.

If you don’t speak MTF, don’t worry. It’s not hard. Higher on the vertical axis is better. Dotted and solid lines of the same color close together are better (far apart is astigmatism). The horizontal axis goes from the center of the lens at “0” to the edge of the lens at “20”.

Legend for all the MTF graphs


Painting with a broad brush, the MTF graphs show that one thing that most people assumed is accurate. At 70mm, the Nikon 24-70 f/2.8 G isn’t quite as good as the other three lenses. The Nikon 24-70 is a good lens, but the other 3 are absolutely awesome lenses.

The MTF charts showed several things that I didn’t expect, though. First among those is that the Canon 70-200 f/2.8 IS II is actually a bit better at 70mm than the Canon 24-70 f/2.8 II. Imatest results on a large number of copies gave a slight edge to the 24-70.

There are a number of reasons for the difference. First, optical bench tests are done at infinity focusing distance, while the Imatest results were at about 15 feet. Second, Imatest shows only the MTF50 — a snapshot along the 0.5 line on the vertical axis of the MTF chart. Finally, Imatest results show a lot of averaging that the MTF graphs don’t do. I usually lump the readings for center, average of the entire lens, and average of the corners, for example. Additionally, Imatest doesn’t separate out astigmatism (the difference between sagittal and tangential lines). On the other hand, Imatest can look a bit further out into the corner than on the optical bench does.

Going into this test I expected the Nikon 70-200 f/2.8 VR II was as good in the center as the Canon lenses, which it is. I thought it would be a bit weaker off center, but it’s not that simple. If you look at just the sagittal numbers (solid lines) the Nikon has a steady fall-off, while the Canon gets softer, then sharper. So in the area from about halfway to 2/3 of the way to the edge of the image the Nikon is better, while the Canon gets better out on the edges. The Nikon also has less astigmatism.

Field Curvature

We also ran field curvature tests on all the lenses. If you haven’t seen these graphs before, they’re a bit different than the MTF curves. (You can read more about them here.) Most people think of field curvature in kind of general terms, but tend to forget that the tangential and sagittal fields can have very different curvature and that the curves can be complex or simple. A perfectly flat field is actually rather rare.

The field curvature graphs give us a lot of information about the lens that we can’t really get any other way. Basically these show what the area of sharpest focus across the lens looks like, assuming you had carefully focused on the center point.

Notice the Nikon 24-70 has some significant field curvature. It’s going to be very difficult to get the center and corners both in sharpest focus without stopping down quite a bit. The Canon 70-200 has a more complex ‘sombrero’ type sagittal curvature with a simpler tangential curvature. The Canon 24-70 Mk II and Nikon 70-200 VR II both have impressively flat fields of focus.

The sagittal field curvature on the Canon 70-200 f/2.8 IS II explains a bit about its MTF chart. If you look at the sagittal field curvature graph notice how the area of sharpest focus has curved away from the “0” line between 10mm and 15mm from the center, then curves back so it’s in sharp focus again at 18mm. Now go back and look at the sagittal MTF curves for the lens and you get some idea as to why it gets softer, then sharper, then softer again.

You might have noticed a bit of tilt in a couple of the field curvature examples. These are minor and would be impossible to detect in optical testing. Just to reassure you, below are the tangential and sagittal graphs for a Nikon 24-70 f/2.8 that was tilted enough to be obvious in an image (it is not one included in the testing).

Field curvature graphs for a decentered and tilted lens.

The Best Lens?

Life was nice and simple when we averaged some Imatest numbers and easily declared a lens ‘better’ or ‘sharper’ than another. We can still do that, of course. When there’s a big difference between lenses it’s just as apparent on the MTF bench as it was with Imatest. When we compare a couple of good lenses, though, the information is not so much ‘better and worse lens’, but rather  ‘stronger and weaker points’ of each lens.

These lenses provide a good example. When I just provided MTF numbers, I found the Canon 24-70 f/2.8 a bit better than the Canon 70-200 f/2.8 IS II at 70mm. Very close, but a bit better. Comparing them here my original thought was things might be different at infinity focus compared to the closer focus used for Imatest. But the additional information we get with bench testing shows us more than just better or worse. The 70-200 is a bit sharper in the center while the 24-70 has a much flatter field.

If you look at the MTF chart there’s not much question the Canon 24-70 has a higher MTF than the Nikon 24-70 in most locations and at most frequencies. However, the Nikon has less astigmatism in the outer areas, and that may give it a ‘look’ that some prefer over the absolute resolution of the Canon.

Before doing this test, if you had asked me I would have told you I thought the Canon 70-200 was just a bit sharper than the Nikon. It might be, by just a tiny bit in the center. Away from center, though, the Nikon 70-200 is better at higher frequencies. The Nikon 70-200 also has less astigmatism in the outer edges and a flatter field than the Canon.

The field curvature in the edges of the 70-200 f/2.8 IS II at 70mm would make some people (including me) prefer the very flat field of the Canon 24-70 f/2.8 Mk II, at least at 70mm. It depends what you use the lens for. For portraiture or action sports, it would be completely meaningless but I do some architectural shooting at 70mm.

Saying one of these three lenses is clearly better than the other at 70mm is rather silly. They have some different characteristics; some slightly different strengths and weaknesses. The reality is if I shot Nikon and carried these two zooms, I’d use the 70-200 for work around 70mm. If I shot Canon and carried these two, I’d prefer the flat field of the 24-70 once in a while, need the IS of the 70-200 once in a while, but generally wouldn’t worry about changing lenses to get a 70mm shot.

Still, I find the comparisons interesting, even if not very useful, and we’ll be doing some more.  And who knows — someday when I’m shooting my interchangeable mount 50mpix SLR I might actually be making a decision as to whether I want the Zeiss, Canon, or Nikon lens for it in a given focal length.

Roger Cicala and Aaron Closz


September 2014


Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. 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 Lenses and Optics
  • Mark

    Roger, number one, you are awesome. Love reading your writing.

    While I appreciate this test, I’d love to see you do what at least for me is more real world.

    Test the workhorse Canon and Nikon lenses, 24-70 and 70-200, same as here, but on accuracy of focus and more importantly speed of focus. I had a D3 with the 70-200 and then the 1dIV (now the 1Dx) and I found the Canon quite a bit snappier to focus, especially from near to far and vice versa.

    Thanks again for all your great contributions to my/our wonderful hobby.

  • Roger Cicala

    Mika, we test every lens with 3 thicknesses of sensor glass: 1,2, and 4mm.

  • J.C. Oliveira

    It would be nice to see similar analysis of all 70-200 @ 200mm, where seems like there is more of a difference amongst them.

  • skibum5

    I’m somewhat surprised by the 70-200 II vs 24-70 II 70mm results.
    Having used a number of 24-70 II copies and a 70-300L copy and a 70-200 f/4 IS copy I found that my best 24-70 II beat both of those at 70mm center frame, but that it fell behind the others at edges and corners (as did all the other 24-70 II copies). In fact even my 24-70 f/4 IS beat the 24-70 II at FF edges and corners (although not at all in the center). Particularly in the real world.

    Maybe the field curvature of the others actually HELPS them more often fit the depths in various parts of the frame for many real world scenes?

    I’ve seen it said before though that the one weakness of the 24-70 II are the FF edges and corners near 70mm.

  • Mika

    Hi Roger, and thanks for the article!

    Just a quick commentary: you may want to check the edge performance in the MTF setup with an appropriate sensor shielding glass thickness.

  • Roger Cicala

    At the distances you’re speaking of I think air refraction, water vapor, smog, and heat waves from the ground are going to have more effect than the lens itself.

  • I’m a geek and I love your geeky posts, got confused on this one!
    I have the Canon 24-70 f/2.8 Mk II on a 5dM3, specially talking about 70mm.
    It is sharp across the frame for close subjects (around a mile or less), but when I take photos from mountain ranges (center focus) it is only sharp at the center and half frame around it not impressive at all on the edges but I see the hills between me and the far mountains are sharp on the edges, I thought the lens has a strong field curvature. (same for f/5.6 f/8)
    I have done the simple tests mentioned here before and it seems its a healthy lens.

  • Roger Cicala

    Sebastian, we can choose them and scroll through the various – there’s not much change although the MTFs (color) are higher at lower frequencies, of course. These are at 50 lp/mm

  • Roger Cicala

    Sergio, it will be soon. We’re installing a finite conjugate that will let us do that.

  • Sergio

    Is it possible to compare macro-lenses at min. focus distance?

  • Thanks for sharing this info Roger.
    I found it very interesting and this website of your is proving to be a very
    interesting and informative place to visit.

    kind regards

  • Sebastian

    At what frequency are the contrast values measured for field curvature?

  • While it is great to have these comparison test, in the real world you want reliability and usability. I see so many tests suggesting lens a is sharper than lens b, I really do not worry that much. What I do worry about is if a lens is going to cope with the invariable abuse it will get and remain working and in good focus. I have had lenses in the past that after the smallest of knocks would end up de-centered, focussing badly or simply not working at all. When we get to lenses of this class the difference in sharpness and contrast really are too minor to worry about.

  • Josh K

    Very excited to see the Olaf Optical Testing website, I know a couple of people – myself included – that would be very interested in a lens testing and calibration service! I was under the impression that you weren’t entirely sure if that would be a profitable venture but clearly there was a change of heart somewhere along the way.

    As for this test, very interesting results. Always neat to see the comparison of outright sharpness vs astigmatism levels. I wonder if there is a way to compare the two in a series of photos?

  • Avo

    This sounds like someone is tempted by the D810 to switch…heehee, is that right?

    I am in the same shoe, owning the 5D3 and the 2 Canon you mentioned above. The quality of the lenses is what is stopping me at the moment. And your article kind of confirms that.

  • Scot Thomas

    Very interesting. So how much “good” does the lens correciton profile in Lightroom do? How would someone even “measure” that?

    Lightroom must perform some stretching and thus add some distortion. But it must be making something about the image better. Doesn’t it? Or does it just help for really crapy lenses?

    Interested to hear people’s thoughts.

    More interested to hear what might be measured or measure-able for this.

  • James Scholz

    Roger, my question was the same as Dr. Crouble’s about which way the curvature of field is aimed. Going forward it might be very useful for people to understand your graph if you placed a camera and lens symbol on top of each graph. That way people who did not hear his question and your answer would still be able to read the information correctly.

  • Massimo

    Do you think the tamron 24-70/70-200 come close to the “brand” names? Would be cool to test out the zeiss $20K cine zooms just for kicks.

  • I was about to comment something like:
    “so, when can I send my lenses in, to get some nice charts for them?”

    Great to see you are caving in 🙂
    I’m pretty sure many people like the idea but won’t be ready to pay the price, but still, some will.

    One interesting piece of information that can come out of this: a comparison of your lenses vs our lenses. I bet you are keeping them in better shape than most people (though maybe not the people ready to pay the price to get them tested).

  • Roger Cicala

    Dr. Croubie,

    An upward curve on our graph (focus moving forward) means the field would actually be curving back toward the camera. I think – it’s very early so my mind is rather uncaffeinated.

    As to the testing, it’s coming. http://www.olafoptical.com Right now we’re just working with businesses, but when I can get things set up we’ll have a web page where you can send your personal lens in. I have to have a comparitive database first, though, and that takes some time. Right now I’ve got maybe 18 lenses out of some 200 done.

  • Roger Cicala

    It’s coming soon, Jeremy. Great minds think alike!

  • SoulNibbler

    Ya know… since you mentioned Zeiss, It would be interesting to see how the cinema zooms compare. Not that anyone would be directly buying them for stills but you do rent the compact zooms.

  • Thomas

    Nice work as always Roger!
    Regarding your troubles with the Sony lenses (and I suspect others these days with the prevalence of focus-by-wire), have you looked at building something like the novoflex reverse eos adapter? (https://www.novoflex.com/en/products/macro-accessories/reverse-adapter-eos-retro/)
    I actually DIY’d one of these myself, great fun for mucking about with macros. As long as could add the electronic contacts into the sony mount of the Imagemaster without messing with the calibration, you could run a wire to any sony body to get the focus-by-wire working.

  • Jeremy

    Could you throw on a Pentax DA70 or a Sigma 70macro to compare, to address the age ol’ zoom/prime debate? These lenses are the ones that usually are talked about as being as good as primes.

  • Jason

    Roger, you’re treading on dangerous ground here, directly comparing lenses across different companies… but we love it! It’s good to see the 70-200 from both companies are so evently matched, however I’m not really seeing the astigmatism in my photos. Would love to see a post about the effect of astigmatism at different frequencies.

    ps. would be great to throw the Tamron 24-70 into the ring as well.

  • Dr Croubie

    ps, I know it’s been said before, but there’s definitely a market for a lens testing / tuning service, nerds and fanboys seem to have lots of money to spend these days. If you don’t start one soon then I’ll almost consider kickstarting one of those benches myself.
    (not that I’d use it myself, since I’ve started on 8×10″ all I do is f/64 and be there)

  • Dr Croubie

    Great work as always Roger.
    Just a question on the field curvatures, I know you said last article you wouldn’t quantify anything, so I’m just looking for something qualitative.
    Take the ‘smiley face’ field, eg Nikkor 24-70, and focus on a point in the centre. Does that ‘upwards curving’ field mean that the edges are sharper ‘closer’ that the centre point, or ‘further’ away?
    Knowing this would definitely help in the setting of some more creative hyperfocal distances, especially for landscapes (eg focus at infinity and the closer edges are in focus so stop-down until the edges are ok at infinity, vs focus closer so the edges are in focus, then stop-down until the centre is ok at infinity).

  • Roger Cicala

    Todd, we’re trying to figure a way. Unfortunately the Sony lenses, without electronics active, won’t focus to infinity.

  • Todd Godwin

    I’d love to see similar numbers for Sony’s offerings in this range.

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