Metabones Speed Booster Ultra review – Part II – Canon EF 50/1.2 L
You can read first part of the review here – http://www.verybiglobo.com/metabones-speed-bosster-ultra-review-part-i/
For comparative part of the review, I decided to go with Canon EF 50/1.2 L .
Changing lenses on the adapters and especially using LTII without aperture control, while trying to shoot real life images is simply too challenging and it might cause serious damage to my cameras. But don’t worry, this comparative part of the review, should give you solid idea about adapters performance and in the following parts, I will test Speed Booster Ultra with many more lenses.
Canon EF 50/1.2L is one of the lenses that I tested initially when first Speed Booster was announced, and while I was overall impressed with system performance, there were some shortcomings, mainly hard vignetting at small apertures and smearing in the extreme corners. If you are interested, you can check that initial review here – http://www.verybiglobo.com/metabones-speed-booster-review-nex-7-part-iii-canon-ef-50-f1-2-l-usm/.
Now with Speed Booster Ultra, I was curious to see if those shortcomings were improved.
First test is boring ISO 12233 chart visual test, which however can tell us few useful things.
My testing procedure is based on a custom made calibration system using professional 80x60cm ISO enhanced 12233 chart for measuring resolution up to 4,000 lines per picture height (l/ph). I pay special attention to align chart to the sensor plane, and of course to ensure vibration free RAW captures. If you have any questions about my testing procedure, I will try to answer them.
Despite all my efforts to make lab test images relevant, there are too many variables that I can’t control as I’d like, one of them being sample variation and/or, mount tolerances e.g. However, both of those objective issues, refers to producer quality control, and if they don’t care enough about it, they should also be ready to see disputable results from time to time.
First what I was curious to see was performance wide open. Bellow are 100% crops at wide open aperture.
Sony A7 with Metabones Smart adapter III is overall most even performer across the frame, but we can also see that Speed Booster Ultra is close second and Lens Turbo II staying behind, mainly because of the glow wide open. I spent quite some time looking at chart results and there is one thing that I noticed – all three focal reducers have some kind of wavy performance. You can see one being better at top right corner e.g., but just 1-2 cm nearby, it is worse than others. While Speed Booster Ultra has much better extreme corners than its predecessor, nearby zone just before extreme corners is slightly weaker.
UPDATE: After publishing this review, I got a PM from Mr. Brian Caldwell, creator of Speed Booster Optics who have good point about test above:
“ I have a comment regarding focal reducer testing. Although it is certainly of interest to test focal-reduced lenses on APS-C vs non focal-reduced on fullframe, this is ultimately a losing proposition, with the possible exception near the center of the image. After all, to achieve parity the focal reducer would have to improve the image by a factor of 1.5x in linear dimensions. This leads many people to falsely claim that any glass adapter will reduce lens quality.
However, comparing a lens that is focal-reduced vs plain on the same format (APS-C) can give a very different result, and is a better measure of how the focal reducer actually impacts the performance of the lens.“
Bellow is comparison table made according to Brian’s proposal.
Following crops In the first column) were made using Sony A6000 + Canon EF 50 f/1.2L USM + Metabones Smart adapter III. To equalize FOV, I had to move camera further from the chart. Presented results are for f/1.2 on Canon withSmart Adapter III and 0.95 on focal reducers.
We can clearly see here the effect of the Metabones Speed Boosters, especially in the center, where image is much sharper. The only area where bare lens beats focal reducers is the zone D.
There are other possible issues that might affect results, mainly mechanical mount tolerances and of course sample variations. Don’t forget that if my original lens has some flaws, like de-centering e.g. focal reducer will most probably emphasize that.
Canon EF 50/1.2L is one of the worst rated Canon L lenses in almost all web reviews that I have read, especially when it comes to the corner performance wide open. However if you look at the Sony A7 results, it doesn’t look that terrifying.
We can also notice greenish corner cast on both Speed Boosters but also on Lens Turbo II. This is most probably caused by combination of light fall off, and steep light ray angles, hitting sensor edges. On this chart test, that greenish casting looks pronounced, but in a real life shots, you will hardly notice it. Making a counter corrective mask in Photoshop should be also very easy.
To see if and how corner performance improves with lens being stopped down, I would like to show you another two 100% crop images at f/2.8 and f/5.6
As you can see, already at f/2.8 corners and even critical zone – D are much improved, but on the other hand, not even at f/5.6, they become crystal clear. Comparing three focal reducers, I would say that Speed Booster Ultra has slight edge, but nothing extremely significant like when wide open.
But when we use bare lens on A6000 (moving camera further from the target to equalize for FOV), results are slightly different, but bare lens still have slight edge, except in the center of the frame.
When it comes to CA, all three focal reducers shows some, but that is to be expected, because EF 50/1.2L is under corrected in that regard (as many super fast lenses). Speed Booster I (Original) however shows most pronounced purple fringing. In fact, lens Turbo II seems to show least CA of all three.
All three focal reducers slightly increases barrel distortion, with Speed Booster I being most obvious. Here are images with superimposed grid for better reading of distortion. First, original lens distortion on Sony A7 without focal reducer.
Speed Booster Ultra
Speed Booster I (Original)
Notice also hard vignetting in the image above, that is removed with new version of Speed Booster Ultra.
Lens Turbo II
Let’s take a look at resolution and possible CA and fringing problems in a real life situation.
Please accept my apologize for choosing rather boring subjects. Most of my favorite testing sites (local parks and view points) are closed in November and they will re-open on April next year 🙁
Scene 1 – focus distance just before infinity. Zone marks.
Aperture f/5.6 was selected to increase DOF, and in reality, image like this should be taken with lens stopped down even more – to f/11 or even f/16. With Metabones Speed Boosters, you will be able to dial f/11 max, but don’t worry, that’s just game of reported numbers. Lens starts at f/1.0 while in reality it is “only” f/1.2, so it has to end one stop sooner too at f/11 instead of smallest native aperture – f/16. (Aperture is either fully open at f/1.0 or fully closed at f/11)
You can examine crops above, but IMO, Metabones Speed Booster Ultra is clearly superior in all zones. Sony A7 with lens and Metabones Smart Adapter delivers sharpest image across the frame as expected.
Metabones Speed Boosters feature magnification ratio of 0.71x while Lens Turbo II is narrower with its 0.726x. That might sound like not a big deal, but resulting differences in FOV are surprisingly larger than numbers indicate.
Scene 2 – focus distance 10m. Zone marks.
This image was taken at f/11, At this aperture, it is very hard to notice any differences, apart of stronger purple fringing with both Speed Boosters in the zone B. However, Speed Booster I seems to lose contrast too, while Ultra keeps high contrast at all zones.
In conclusion, I still prefer Speed Booster Ultra between the three, but differences are negligible and Lens Turbo does very well, especially in terms of CA, namely PF control.
Scene 3 – focus at infinity. Zone marks.
In this last comparable image, we can see that at infinity and fully closed aperture, differences between adapters mostly disappears. What we can also noticed, is that Sony A7 with a bare lens mounted, still has the edge in contrast and resolution (look at zone B e.g.)
With Speed Booster Ultra, problems with hard vignetting are gone now
Lens turbo original was known for the problem called blue spot. It seems that version II is improved in that respect, but in comparison with Speed Boosters, it stays behind both. Speed Booster Ultra on the other hand is much improved in that regard, leaving original Speed Booster I, somewhere in between.
Coming to the end of this comparative Speed Booster Ultra review, with a Canon EF 50/1.2 L, I’d like to show you one bokeh test effort, that unfortunately didn’t come out as I’d wish, because I used hand held camera and compositions (distance to subject) vary, so comparison is not fair. But you can look at results as they stands for the given distance.
Metabones Speed Booster Ultra
Pros: Good sharpness across the frame up to the extreme corners, best contrast, best flare resistance, very good build quality, tripod foot, easy to mount, good magnification, electronic coupling of aperture, IS, and AF to certain extent.
Cons: AF is not 100% accurate and it is very slow, price is very high, there are problems with infinity focus with some lenses, mainly Zeiss ZE ones (I still have to try adjusting adapter to improve infinity focus, but from initial test it was way off for Zeiss 21/2.8 ZE), purple fringing could be lower.
Metabones Speed Booster Ultra, improves on its predecessor in almost every aspect, however, original Speed Booster remains slightly sharper in some image areas including center. That’s probably because of changed field curvature characteristic that was used to improve extreme corners and get rid of vignetting. Ultra has more even sharpness across the frame and that is certainly more important than absolute sharpness in one or two zones. Superior optics are significant step further in bringing full frame lens experience to APS-C camera users, and it is quite amazing how far Caldwell optics were able to come. Of course, bare lens on A7 still has the edge, but in a real life, that edge would be hard to see. The price is high, but for it, you will get best available focal reducer on the market , with electronic control allowing unlimited use of Canon EF lenses (except AF, that is very limited). Possibility to change aperture from camera and use all shooting modes as intended, as well as possibility to engage optical image stabilization (for IS lenses), makes Metabones Speed Booster Ultra clear choice for us, who are still keeping bunch of Canon lenses, but who are using mirrorless cameras more often. Despite the price, I can highly recommend this adapter!
Zhongyi Lens Turbo II
Pros: Affordable, good IQ when stopped down, best control of CA and distortion.
Cons: Build quality is not top notch, handling (mounting adapter) is strange and you’ll have to get used to it, once mounted, adapter wobbles quite a lot, flare resistance could be better, FOV is narrower than with Speed Boosters.
Lens Turbo II, while optically inferior to Speed Booster Ultra at wide open apertures, is actually not overall bad option. It’s optical qualities improves stopped down, to deliver quite nice IQ with tested lens. Beside lower build quality in comparison with Metabones, using this adapter with native Canon EF lenses, is possible only wide open, unless you want to go through troubles by changing aperture on the lens mounted on another body. In practice, that would be simply ridiculous and thus I can’t recommend Lens Turbo II for Canon EF lenses.
If you however consider focal reducer, but you are not sure which mount standard to choose, Lens Turbo II in EF to E mount, can be interesting option, because with the exception of Canon FD, Minolta MD and Sony A mount, you’ll be able to use it for most other usual mount standards with a simple ring adapter. (Olympus Om to Canon EOS e.g.)
Metabones Speed Booster Original can be another valid option, if you can find it for a good price on the used market. It was and still is great focal reducer, with only extreme corners being problematic with few lenses (smearing and most importantly vignetting.)
In the following parts of the review, I will try to make test shots with Metabones Speed Booster Ultra and several other Canon EF lenses. (and some legacy ones, such as Contax Zeiss 50/1.4.)
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