Many apologies for the delay, I know how annoying it can be when people flake out on stuff like this. In any case, without further ado, the results of my comparison between the Yongnuo 2x III and the Canon 2x Mk III.
Build Quality
The extender seems reasonably well built and even includes a gasket on the lens mount side. It's easily distinguished from the Canon version by the red anodized ring on the front surface. The outer shell seems to be made of a cheaper plastic than the Canon (I couldn't tell if the Canon is actually plastic or metal) as you can feel it flex and shift much more than the genuine article.
The 70-200ii is the only lens that I've tested this with as I don't normally shoot long focal lengths and this whole endeavor is really just a curiosity for me. The first copy of the teleconverter I received showed a bizarre behavior where it seemed to give great results while shooting test charts in my office, but once I took it outside and shot at longer subject distances the results were pretty terrible. I was able to get a second copy and I'm happy to say that the results are much better! I also was able to borrow a Canon 2x III although I only had it for a short time and so the comparison between the two is not exactly exhaustive.
The results shown below are all done with the 70-200ii mounted on a 5D3 @ 200mm (400mm with the 2x extender). I used live view autofocus for each shot with the focus point in the center for the center samples and the focus point moved to corner for the corner shots. All shots were tripod mounted with IS turned off. The light was changing quite a bit so the shutter speeds aren't all the same but I don't think it had any effect on the results. Results are shown for both the center and the corner at f/5.6, f/8, and f/11.
Center at f/5.6 : I can't really see any difference in sharpness here although maybe the YN has very slightly higher contrast.
Center at f/8 : I can't see any difference between the two.
Corner at f/5.6 : The Canon appears very slightly sharper with a bit less CA, but not much difference.
Corner at f/8 : By f/8, they appear the be equal to my eye.
Corner at f/11 : The Yongnuo seems to have sharpened up nicely but it seems like the Canon is actually getting softer as I stop down. Maybe field curvature issues or a mistake on my part?
The Yongnuo doesn't seem to completely report as a teleconverter as the focus speed doesn't slow down at all whereas the Canon shows a noticeable decrease in focus speed, even on my 1D bodies. Single AF seemed fine even without an AFMA. I tried doing a little BIF and the results were not great, but I think that's mostly due to my inexperience with that kind of shooting so take that with a huge grain of salt.
Conclusion
Yongnuo's first forays into optics (see also their 50 1.8 copy) seem to be pretty decent. I'm a little bit confused about the corner performance of the Canon 2X III as it seemed to get softer when stopping down and the only thing I can think of is that there's either some field curvature issue or I made some gross error in my setup. In any case, the performance of the Yongnuo seems really good for 38% of the cost of the Canon, although I'm not sure how good the AF is and I really doubt I would trust the weather sealing. Please ask questions if there's anything I've missed that you would like to know and I'll answer if I can.
whumber, thanks so much for posting those shots. My Canon 2x Mk II died recently and funds don't stretch to a Mk III so I'm going to go for a Yongnuo in the meantime until the Mk III second-hand prices drop a bit*. Your post give me the confidence to give it a shot from Amazon.
* Here in the UK a second-hand, unboxed, Mk III is still over twice the price of a new Yongnuo.
I managed to scrounge a recently-serviced Canon 2x II ( no III, unfortunately ) to start some tests against a new Yongnuo III.
I'll add images here as weather & conditions permit testing to proceed. Unfortunately the Irish Summer doesn't often comply.
Direct 1:1 crops from the CR2, saved as 100% quality JPEGs for display here. Letters in top of images indicate the manufacturer.
Five images were taken for each Extender and the best one for each selected for comparison.
Test 1: Centre-frame sharpness, wide-open
Exposure: f/8.0 1/2500 ISO 800
Target: White reflective 15-cm ruler at 40 metres from lens hood.
Method: Tripod, locked gimbal-head, mirror lock-up through Live View, 10-second countdown shutter. IS off to remove variance.
Environment: Exterior Sunlight, Sun directly behind camera.
Nice, thanks for sharing this. Any idea why the ruler colors are so different?
I would be curious to see a Kenko 300 Pro 2x DGX compared with the Yongnuo and Canon 2x III. I just received mine to use on my Sigma 500mm f4.5 and not only does it retain all AF points at f9 but from what I can tell so far IQ is very impressive.
architect7 wrote:
Any idea why the ruler colors are so different?
Good point; white balance temperature for both shots was exactly the same at 5075 Kelvin. So I assume the coatings on the two Extenders are responsible for the difference.
Weather looks promising for some closed-down-aperture tests of the same target later today.
Couldn't wait for the Sun to emerge again so repeated the tests under gloomy, but consistent, light. This time at f/10.
Same setup as before, Live View with MLU and remote trigger etc. Shutter speed was 1/320 at ISO800. Five shots each at 10 second intervals, picked 'sharpest' for each by eye.
Yongnuo on left, Canon II on right. Yes, same exposure settings... interesting tonal differences.
After a couple of weeks of experimentation my findings on the Yongnuo 2x III are:
Positives
1. Very good performance for the money, almost as good as the Canon II and yet cheaper than a used example.
2. No discernable AI Servo issues, focus seemed as quick and accurate as with the Canon and actually suffered fewer 'hang-ups' when the Canon refused to try to focus until nudged with MF. My main targets were aircraft and occasional passing birds.
3. Well-built.
Negatives
1. Can't quite match the Canon II at centre-point so likely to be worse than the III, though at less than half the price.
2. Occasionally my 1D4 became confused as to minimum aperture, showing 4.0 when the Yongnuo was attached ( actual minimum being 8.0 ) but exposing at 8.0 when shot ( per the demands of physics! ).
3. Apparently lower light transmission than the Canon II which results in darker exposure.
4. Not weather-sealed as far as I could determine.
5. Less internal flocking than the Canon II.
Still a great buy. I'll probably hold on to my copy as a back-up, as I use a 2x every day.
Snopchenko wrote:
The 35/2 is both 25 years old and discontinued by Canon, all right, but the 50/1.4 they also copied is neither. Or the extender in question.
I almost smell the burning...
The 50mm f/1.8 II that the Yongnuo 50mm is a "clone" of (though it seems to perform better) was introduced in 1991. It's not quite 25 years old, but it IS 24.
Even IF there was a patent on the design (which isn't a given) it would have expired 17 years after issuance unless it was issued after 1994 in which case it would have expired 20 years after filing.
You buy a TC based on performance, not appearance.