# Delivery of the Canon 1.4X III HAS STARTED



## jdgagne (Dec 18, 2010)

I have pre ordered a new 1.4X III back in October at the Camerastore. They have received some pre orders including mine on last Thursday.

Looking forward to do some tests with the big white.

JD


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## kubelik (Dec 31, 2010)

Bryan over at The Digital Picture has started to do testing on the new extenders:

http://www.the-digital-picture.com/News/News-Post.aspx?News=543&Title=First-Looks-at-Canon-Extender-1.4x-2x-III-Image-Quality

looks like fairly significant difference in enhanced contrast and reduced CA, although no major wonders in terms of sharpness. I'm going to be looking forward to seeing more detailed tests as I'm also in the market to pick up one or both of the new teles


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## pgabor (Jan 1, 2011)

Extenders enlarge the flaws of any lens, but the 200mm f2.0 is THE perfect lens, so no surprise that we cant see a big difference, but i bet that on for example the new 70-200, the improvement will be more obvious.


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## UngerPhotography (Jan 1, 2011)

> Extenders enlarge the flaws of any lens, but the 200mm f2.0 is THE perfect lens, so no surprise that we cant see a big difference, but i bet that on for example the new 70-200, the improvement will be more obvious.



This is what I am waiting to hear. I plan on getting a 2x III for my 70-200 regardless as I thought the 2x II did a great job, but I am hoping to hear that the improvements make the price worth it.


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## epsiloneri (Jan 6, 2011)

pgabor said:


> Extenders enlarge the flaws of any lens, but the 200mm f2.0 is THE perfect lens, so no surprise that we cant see a big difference, but i bet that on for example the new 70-200, the improvement will be more obvious.



This sounds backwards to me. Surely extenders are not able to _correct_ lens flaws? For a "perfect" lens I would expect it to be easier to differentiate between the II and III extenders, as any flaws _added_ by the extenders would be more visible. On a less perfect lens, however, any extender flaws might be masked by the magnified lens flaws.


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## neuroanatomist (Jan 6, 2011)

epsiloneri said:


> This sounds backwards to me. Surely extenders are not able to _correct_ lens flaws? For a "perfect" lens I would expect it to be easier to differentiate between the II and III extenders, as any flaws _added_ by the extenders would be more visible. On a less perfect lens, however, any extender flaws might be masked by the magnified lens flaws.



Regarding extenders 'correcting' lens flaws, to some extent they can, similar to the way in which a crop sensor 'corrects' flaws - with the extender, you're using only the center portion of the lens' image circle, meaning soft corners on a lens are not part of the image (although the extender adds it's own corner softness). Likewise, vignetting is reduced with an extender, and since the extender adds a bit of barrel distortion that tends to cancel out the mild pincushion distortion seen with some telephoto lenses.

But overall, extenders do decrease image quality - the issue at hand is do the MkIII extenders decrease IQ less than the MkII versions, and for that comparing them on a 'perfect' lens might not be the best test. Think of if like this - hypothetically, if the MkII extender has a 'flaw factor' of 4, and the new MkIII extender is better, it has a lower 'flaw factor', let's say 3. Now, if the 200/2 is 'perfect' it has a 'flaw factor' of 1 so the difference between the two extenders is 1 unit (4-3). The 70-200 II is not perfect, but close - let's say a 2. Now, the difference between the extenders is 2 units (8-6) - more obvious. 

But, it's probably not a nice linear relationship like that - for example, even though the 70-200mm f/4L IS and 70-200mm f/2.8L IS II lenses are pretty similar in IQ, the MkII extenders degrade IQ a little more on the f/4 lens than on the f/2.8 lens, independent of the aperture differences. So, I suppose the best bet is to wait until comparisons of MkII vs. MkIII extenders are available for the specific lens(es) with which you plan to use the extenders.


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## kubelik (Jan 6, 2011)

epsiloneri said:


> pgabor said:
> 
> 
> > Extenders enlarge the flaws of any lens, but the 200mm f2.0 is THE perfect lens, so no surprise that we cant see a big difference, but i bet that on for example the new 70-200, the improvement will be more obvious.
> ...



I believe the original intent of the word "improvement" was meant as "improvement of the III series over the II series extenders", not a reference to improving the absolute quality of the lens image.


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## epsiloneri (Jan 7, 2011)

Aha! Now I see why you think the way you do. But that doesn't seem like a proper model for how an extender works. I'm sorry I wasn't very clear. I think the following sounds much more reasonable:

Let's say "perfect" extender merely magnifies the central field given by the lens (may it be 1.4x or 2.0x), without otherwise modifying it. If we focus on resolution, then it should not change the resolution in terms of smallest resolved detail. That is, the point-spread function (PSF) would not change in angular size; on the sensor, on the other hand, the PSF would be magnified by the given magnification factor (1.4 or 2.0), so in terms of resolution per pixel, the PSF would be larger by the same factor (and thus the image appear less sharp, if the PSF is resolved by the pixel density of the sensor, of course).

Now what happens if the extender is not perfect, but adds its own fuziness? You seem to imply that the magnification factor of the PSF will change, but that doesn't seem reasonable. More realistically, the PSF of the extender will be convolved with the PSF of the lens; if the PSFs can be crudely approximated by Gaussians, the lens PSF has the full width at half maximum (FWHM) of A, and the extender a PSF FWHM B, then the combined PSF would have a FWHM C = sqrt(A^2 + B^2). (in reality the PSFs are far more complicated than simple Gaussians for non-diffraction limited optics, but this gives an approximate scaling behaviour)

Back to your example. Let's say the PSF of the 70-200/2.8L II (FWHM=2) is twice that of the 200/2L (FWHM=1), and that the extender MkII (FWHM=1) is twice that of MkIII (FWHM=0.5). Then the improvement from using the 2.0x MkIII instead of the MkII on the 200/2L would be

sqrt((2*1)^2+1^2)/sqrt((2*1)^2+0.5^2) = 1.0847, or an improvement of 8.5%.

For the 70-200/2.8L II, on the other hand, the improvement would be much smaller:

sqrt((2*2)^2+1^2)/sqrt((2*2)^2+0.5^2) = 1.0445, or an improvement of 4.5%.

Simply put, *the greater the imperfections of the lens, the more they mask the small imperfections added by the extender*. That is why I think it's a better to use as good lens as possible when testing for any potential differences in resolution generated by the extenders.

I don't know how the PSFs of the extenders compare to the PSFs of the lenses, but I would expect their contribution to be relatively small. That is to say, there is not much room for improvement, as the "lens flaws" themselves dominate the detoriation of resolution per pixel with magnification.

Finally, there is an easy way to measure PSFs. Just point the lens to a point source, and the resulting image will be the PSF. Unless you have a diffraction-limited telescope of aperture > 5 cm, bright stars at night make excellent point sources. Just take care to expose for short enough time or use a tracker to compensate for the Earth's rotation, otherwise stars will be motion blurred. A properly dimmed laser-pointer from a distance could also work, I guess.


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## neuroanatomist (Jan 7, 2011)

Actually, I was using a hypothetical catch-all term 'flaw factor' precisely because there's more to IQ than the resolution you're measuring by determining PSF (something I've never tried with a camera lens, although I have done empirical PSF measurements to drive deconvolution calculations in multiphoton microscopy). Spatial resolution does not account for the effects an extender has on distortion, vignetting, CA, etc., some of which may actually be beneficial to overall IQ, and some detrimental. 

In principle, though, while I was trying to explain what I assumed was the logic behind the assertion that you should use a worse lens to see differences in the extenders, I don't think that's necessarily the case in a mathematical sense. However, practically speaking, with the 200/2 it is difficult to detect any difference in center sharpness when stopping down from f/2 until sensor diffraction starts to play a role, yet based on optical physics we know that resolution should increase with decreasing aperture. That suggests the difference are less than the lower limit of quantification for the testing. 

Let me offer a real-world example from TDP's ISO 12233 crops. Hopefully we can agree that the 2x extender will have a greater negative impact on sharpness than the 1.4x extender. Here are two comparison links:

200mm f/2L IS with 1.4x II vs. 2x II @ f/11

70-200mm f/4L with 1.4x II vs. 2x II @ f/11

As you mouse-over the respective comparisons, does one set appear to have a greater differential across the frame than the other? 

To borrow a method you proposed previously comparing images based on the SD of the pixel intensity, and with caveats that this is n=1 and there are underlying assumptions about consistency of conditions across multiple testing sessions, from Bryan's images there's a 25% greater reduction going from 1.4x vs. 2x with the 70-200/4 zoom than the 200/2 prime, even though the absolute values are higher with the prime, consistent with the 200/2 having better resolution.


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## epsiloneri (Jan 7, 2011)

neuroanatomist said:


> Let me offer a real-world example from TDP's ISO 12233 crops. Hopefully we can agree that the 2x extender will have a greater negative impact on sharpness than the 1.4x extender.



Not really  Of course, I agree that the 1.4x sample looks sharper than the 2.0x sample from the links you provided. But these are 100% crops, and to achieve the same projected size on the sensor, the test chart has been moved 1.4x further away for the 2.0x TC (compared to the 1.4x TC). Therefore, I cannot tell from these tests how the angular resolution is affected by the TCs. It's not surprising that you see more detail if you move in closer!

A proper way would be to shoot these test charts at the same distance and then determine the angular resolution, e.g. by how much detail can be seen in the test charts. I browsed around a bit but couldn't find anything better than this experiment. Perhaps you know of similar TC tests where the angular resolution is measured - I would find that helpful.

Yes, going from 1.4x to 2.0x on the 70-200/4L (and moving the target further away) decreased the IQ more than doing the same on the 200/2L - but that's probably because the 200/2L is intrinsically sharper, and does not reflect how much of the deterioration is due to the TCs.


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## epsiloneri (Jan 7, 2011)

Coming to think of it, in some cases there is a way to reproduce the image of a perfect TC, and that is to crop an image on a sensor with a pixel density that is greater than the resolution provided by the lens, that is, an image that is oversampled. Applying a TC under those conditions would be useless for that particular sensor (cropping would produce better results, except perhaps for dynamic range), but it would be a way to determine the effects of a TC for sensors with much larger (non-outresolving) pixels.

I hadn't heard of multiphoton fluorescence microscopy before, sounds pretty advanced. Unfortunately I expect the PSF to be much less well behaved for camera lenses (in particular zoom lenses), with weird shapes that change across the field. Having objects at different distances would also complicate matters. Otherwise it would be cool to try out deconvolution to squeeze out some more detail. I know the police force use it to sharpen up motion blurred license plates, but those PSFs are then simpler. In one case a few years ago they used deconvolution (sort of) to reconstruct a strongly distorted picture of a child molester (submitted by the villain himself). Very impressive work.


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## kubelik (Jan 13, 2011)

bryan's updated the ISO charts some more (although still not with the lens I want to see most, the 70-200 f/2.8 L IS II) ... the effect seems to vary by the lens, but overall with the 2X teleconverter there seems to be some slight improvement, mainly in the corners and edges of the frame. the effect on CA and contrast seems to vary somewhat lens-to-lens as well, with some showing better color and contrast with the 2x II and some showing much better with the 2x III, although overall definitely favoring the new 2x III.

still looking forward to picking up the teleconverters, especially if there's an additional AF improvement, that's not something you can show with ISO charts


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## torger (Jan 13, 2011)

I've always wondered but not found any good comparisons if it is generally better image quality to use 7D body with 1,6 crop instead of 5Dm2 + 1.4x teleconverter. The teleconverter is of course more practical, portable and cheaper than a teleconverter, but say you already have a 7D for action and 5Dm2 for landscapes/portraits, does it then make sense buy a teleconverter for the 5D, or is one better off concerning image quality bringing the 7D and switch bodies to get the extra reach?


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## kubelik (Jan 13, 2011)

Torger, if you look at the ISO charts on The Digital Picture, for some of the lenses at least you should be able to make exactly that comparison. Select the same lens on both sides. On one side, change the camera from a FF to a crop body. On the other, pick one of the focal lengths that come from using a 1.4x extender.

My guess is the crop body should be preferable to using an extender, simply because you're not adding extra elements that light has to pass through.


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## neuroanatomist (Jan 13, 2011)

torger said:


> ... does it then make sense buy a teleconverter for the 5D, or is one better off concerning image quality bringing the 7D and switch bodies to get the extra reach?



The crop sensor will provide better IQ than the teleconverter (and much better IQ than cropping your FF image). That's one reason why I have exactly the setup you mention - a 5DII for portraits/landscapes, and a 7D for birds/wildlife/sports.


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## epsiloneri (Jan 14, 2011)

neuroanatomist said:


> (and much better IQ than cropping your FF image).



Because of the higher pixel density? Apart from pixel density, I would expect the cropped FF image to be equivalent to the crop-camera.

As I wrote above, a crop can be considered close to the "perfect" TC. The exception is dynamic range, since the sensor well depth scales with surface area. So in some exceptionally contrasty scenes, I can see a FF+TC combo being better suited.


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## neuroanatomist (Jan 16, 2011)

epsiloneri said:


> neuroanatomist said:
> 
> 
> > (and much better IQ than cropping your FF image).
> ...



I agree that a crop sensor is fairly analogous to a 'perfect' TC.

When you have some time, give THIS THREAD a read.


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## epsiloneri (Jan 16, 2011)

neuroanatomist said:


> When you have some time, give THIS THREAD a read.



Thanks for the link. I read the thread and was happy to see a healthy technical discussion with actual test shots to verify theory. Now I better understand your statement that cropped-camera IQ is better than cropped FF camera IQ - you were referring to the specific examples of 5D2 and 7D.


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## kubelik (Jan 24, 2011)

just got the new 2x III from my local photo store and slapped it on my 70-200 L IS II right away ... very happy with the results (and happy I don't feel the need to buy a 100-400 to haul around as well).

waiting for the weekend to take it zoo-testing. I've found that if you crop the 5D II's image down to an APS-H size you get a 12.4 MP image (4320x2880) which is still easily large enough for good prints. cropping it to APS-C means you only get the same resolution as my old 30D. if anyone's interested I'll let them know how it goes, but just from shooting random test shots of objects with high contrast and fine detail, I can say that the ISO charts Bryan shot at The Digital Picture are a very accurate representation of the quality of this lens+tele combination.


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## neuroanatomist (Jan 24, 2011)

kubelik said:


> just got the new 2x III from my local photo store and slapped it on my 70-200 L IS II right away ... very happy with the results (and happy I don't feel the need to buy a 100-400 to haul around as well)... if anyone's interested I'll let them know how it goes, but just from shooting random test shots of objects with high contrast and fine detail, I can say that the ISO charts Bryan shot at The Digital Picture are a very accurate representation of the quality of this lens+tele combination.



Comparing 400mm f/5.6 achieved with the 100-400 vs. the 70-200 II + 2x III, Bryan's charts show that the native 400mm is a bit better all across the frame than the shorter zoom with the new extender. 

I'd definitely be interested in some real-world impressions.


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## kubelik (Jan 24, 2011)

neuroanatomist said:


> Comparing 400mm f/5.6 achieved with the 100-400 vs. the 70-200 II + 2x III, Bryan's charts show that the native 400mm is a bit better all across the frame than the shorter zoom with the new extender.
> 
> I'd definitely be interested in some real-world impressions.



I remember someone a while back mentioning that this combination should be as good as the 100-400 at 400 f/5.6, and I remember both of us saying that was very, very, unlikely, almost impossible. I must say I stand largely corrected; it's not exactly the same but it's really darn close. 

even more interesting is this: wide open, if you look at the ISO charts, the 70-200 II with the new 2x is actually better than the 200 f/2 + 2x III wide open. however, at 400 and f/ 5.6, the 200 prime kills the 70-200


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## neuroanatomist (Jan 24, 2011)

kubelik said:


> I remember someone a while back mentioning that this combination should be as good as the 100-400 at 400 f/5.6, and I remember both of us saying that was very, very, unlikely, almost impossible. I must say I stand largely corrected; it's not exactly the same but it's really darn close.



To me, it looks like the difference between the 100-400 @ 400/5.6 and the 70-200 II at 400/5.6 is approximately equivalent to the difference between the 2x II vs. 2x III on the 70-200 II. It's not a huge difference, but it is noticeable. Probably enough that I wouldn't use the 70-200 II + 2x II, but I'd consider the combo with the 2x III if I didn't already have the 100-400mm.


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