Estimated reading time: 11 minutes.
August/2017 – The 100mm f/2 is the third Canon EF mount lens introduced by the Chinese third-party brand Yongnuo, by the end of 2016. Known for it’s low-cost flash heads, radio transmitters and LED illuminators, this manufacturer has been venturing in the lens market, offering a timid line-up for Canon and Nikon cameras, but at extremely attractive prices; welcomed by most photographer. Just like the 35mm f/2 and the 50mm f/1.8 before it, Yongnuo bases its designs and optical formulas on older first-party lenses, to save on R&D thus delivering cheaper products. Now the victim is the 1991 EF 100mm f/2 USM (US$499), a short-telephoto lens made for shooting indoor action, given the long(er) focal length and wide aperture, compared to a 85mm f/1.8. Identical are the 8 elements in 6 groups, but gone are the USM autofocus motor and 2/3 of the price (US$159 on the Yongnuo). Will the Chinese 100mm f/2 be worth a place in your kit, coming from two negative 35/50mm reviews? Let’s find out! Nice reading.
At 7.6 x 8.3cm of 390g of plastics, metal and glass, the first thing we notice on the Yongnuo 100mm f/2 is the identical design to the Canon EF 100mm f/2 USM; including the 1991 ergonomics school despite its 2016 launch date. With a solid plastic barrel on the inside, and fully internal AF operation, the 100mm f/2 build actually impresses by its toughness, without the wobbliness found on other Yongnuo lenses; that misalign on the 35mm f/2 ($99) and 50mm f/1.8 ($67), both sporting moving barrels (one internal, holding the lenses; and an outer shell). With such misalignment it was nearly impossible to take sharp pictures with those, but it doesn’t happen on this newer 100mm f/2 ($159). Without cutting corners on the mechanics, this low-cost Yongnuo is virtually the same product as Canon’s; only for a third of the price.
In your hands the ergonomics are interesting because the “100mm f/2” spec is the last “portable” telephoto distance. What it keeps short it keeps easy and nice to use, to have it with you during the day. The grip is precise and direct, with your fingers always at the focusing ring’s reach, that sits higher on the lens barrel; the typical “cascade” design used by Canon in the 90’s. To the photographers left side there’s an AF/MF switch for engaging/disengaging the internal micro-DC motor, once this lens doesn’t support a full time operation; every time one wishes to manually focus, he/she/it must disengage it from the motor. What’s really curious is how the ring mechanically turns: a counter-clockwise movement produces a clockwise spin on the focusing group, in direction of the minimum focusing distance; and a clockwise ring movement produces a counter-clockwise turn on the focusing group, aiming for infinity; very confusing! It’s comical to see the distance window moving opposite to the external focusing ring, and it asks for a slight learning curve, made even more important given the questionable autofocus performance.
Inside Yongnuo opted for a DC micro-motor, the biggest difference from the ultrasonic Canon EF lens. While it is reasonably quick to focus in SINGLE mode, just like the Canon, this motor uses noisy clogs worse than the silent USM. But the problem is its compatibility with recent EOS cameras, that offer many focusing methods. For instance the EOS 5DS, a 50MP full frame camera based on the 5D Mark III, focusing through the viewfinder is questionable at the very least: front and back focusing issues are constant, with less than 40% accuracy. While Yongnuo’s own instructions manual recommend experimenting with Canon’s AFMicroAdjustment settings, the errors are so random (sometimes front, sometimes back), that it just doesn’t work. And during the AI SERVO continuous focus, the YN 100mm f/2 simply fails to focus: the AF motor doesn’t move in the right direction (!), and refuses to lock. Even worse, sometimes when shooting faraway subjects, for instance from 10m to infinity, the Y100MMF2 don’t even move! I had to refocus the camera to a much closer object (2-3m), and than recompose the shot and try to focus on a distance point. I’d never seen such behaviors, and there’s definitely something wrong with the YN100.
But it’s during the Live View operation, without using the mirror, the Yongnuo 100mm f/2 gets really weird; it’s simply not compatible with most EOS cameras. With the EOS 5DS, the contrast detection focus doesn’t work through the LCD screen: the AF motor moves front and back, and just doesn’t find focus; bizarre! I tried using Live View to compensate for the front/back focus issues, but it just wouldn’t work with the 5DS. With the Canon EOS 6D, on the other hand, it kind of works: using the Live View “quick” function, that raises and lowers the mirror to use the phase detection system, then the Yongnuo works (despite some questionable precision). However using the same EOS 6D’s “flex zone AF” in Live View, that uses the contrast detection just like the 5DS, the Yongnuo 100 mm again doesn’t work. Finally for all-Live View camera’s like the EOS M, the lens absolutely doesn’t work. So check your camera compatibility before purchasing it.
With Canon’s EOS T7i a different logic occurs: the viewfinder works (again, with some eventual front/back focus issues), but the Dual Pixel Live View is near flawless; fast and accurate like no other camera tested! You barely touch the focusing button and the lens “jumps” to the right position; no hunting, no front/back focus; just perfect even under low light. So it’s curious (or annoying?) how the Yongnuo 100mm f/2 behaves with EOS’s cameras, an issue I didn’t notice on the 35mm f/2 (tested with the EOS M) and the 50mm f/1.8 (tested on Sony A7II + metabones Smart Adapter IV) lenses: the contrast-detection Live View just doesn’t work; the phase detection viewfinder works in single mode only; and the new Dual Pixel focus works flawlessly.
Finally at the front the 100mm f/2 copies the original Canon lens ø58mm filters; very easy to find and cheap. They fix on a plastic thread just above the first optical element, that itself sits inside the lens hood thread; unfortunately not included in the box (Yongnuo recommends using Canon’s own ET-65II). At the rear the metal mount is well finished and nice to use, with minimum friction, and the electronic contacts are golden; an step further in durability for this price point. And while we don’t see any sort of rubber seal around the lens, and least the front and rear elements are fixed, preventing dust from getting inside the lens. Overall the Yongnuo 100mm f/2 is fair for its US$160 price tag, certainly a step above the 35/50mm US$60/90. But its questionable usability, with a reversed manual focusing ring; and the weird AF behavior makes it a tough recommendation; it works with some cameras, but can be a pain to keep in a comprehensive kit.
With an 8 elements in 6 groups optical formula, non aspherical pieces nor low-dispersion glasses, and treated with a somewhat “multi-coating” layer, the Yongnuo 100mm f/2 is strictly an EF 100mm f/2 clone; good for its overall performance; bad for some absences in manufacturing. With a simple optical formula, there’s not much to be desired: the center resolution is good even wide open, thanks to the near-double-Gauss lens arrangement; but it drops around the corners, given the lens curvature. The image contrast is surprisingly sharp on most photos, except when we’re backlit or any strong light source appears near the edges. The colors are well saturated and yellowish, an advantage from the low element count. And if it wasn’t for Yongnuo’s bad focusing system, we would definitely see less axial chromatic aberrations. So with an accurate focusing technique, constant file reviews and patience, we can get good images from the Yongnuo 100 f/2.
Wide open and at the frame center, the Yongnuo 100mm f/2 resolution impresses; certainly the all-internal focusing design helps with fewer misalignments. It’s interesting to see how the lower end glasses render good sharpness and details on the US$159 lens, curious to imagine what the first parties deliver on its more expensive designs. Whenever the lens is focused properly, it’s possible the see details on fur, textures, distant objects and graphics, that show a slight fog around high-contrast edges; given the questionable glass finishing. Around the edges the performance can drop when wide open, given the spherical distortion, but it’s visible mostly on geometric compositions, like using the horizon to frame the subject. But overall it’s the same performance delivered by Canon, and a typical advantage of primes: high resolution when focused properly.
Stopping down dramatically reduces the wide open “fogginess”, perfect to enhance the image contrast on graphical signs; or compositions that might include the light source. It’s interesting to see how at f/4-f/7.1 the resolution is great on Canon’s 50MP EOS 5DS, made with large format printing in mind. As the lens features few glass elements, the contrast and color rendering is excellent on street photographs registering culture; something lacking on over-complicated formulas. Despite the lack of a really flat image plane, without absolute resolution from edge to edge, useful to shoot landscapes, it’s a nice performance from Yongnuo. And as it repeats Canon’s EF 100mm f/2 9-blade aperture, the out-of-focus quality is also nice, even when stopped down, smooth despite the busy background; excellent to use the thin 100mm telephoto depth of field.
Chromatic aberrations flirt with the double-Gauss formula: visible on the out-of-focus background, invisible on high contrast edges. As we make due with non-aspherical pieces to guarantee sharpness on varying focusing distances, the front and backgrounds get colored green-purple halos like any wide-aperture prime, no matter the price. It’s an issue to shoot chromed details and strong backlit subjects, that “explode” with colored lines that are hard to fix in post. But the lateral chromatic aberrations are invisible, thanks to the double-Gauss 8-elements arrangement: not even strictly geometric compositions show colored edges, that is great to shoot graffiti and various urban landscapes. It’s an expected performance from the medium-telephoto lens.
The flaring resistance is surprisingly bad on the 8 “multi-coated” elements from Yongnuo. Part of the high price from first parties, like Nikon’s Nano Crystal or Canon’s recent Air Sphere, the chemical glass coatings are still the Achilles Heels on low-cost brands. Absolutely any bright subject near the frame, like a simple sky on mundane compositions, is capable of completely ruin the overall contrast, blooming from top to bottom in most shots; a never before seen such issue with my EOS 5DS. And as it doesn’t show on the viewfinder, it’s a guessing game to when it’s going to happen: you compose your shot, focus and shoot… To be surprised in review with a completely over-exposed file. It’s yet another issue requiring double-checking every YN100F2 photograph.
Geometric distortions are practically absent from the 100mm f/2, not surprising for a medium-telephoto lens. The longer the focal length, the easier it is to design a flat image plane, and this Yongnuo stays true to the rule. It’s perfect to shoot landscapes with the horizon in sight, architectural elements on street photography, or art collections, once the pixel perfect files won’t need stretching from post-processing software. That’s why I call this lens “near double-Gauss”: if it was just two positive meniscus lenses on the object side, and a negative meniscus lens on the image side, we would clearly see some spherical aberration. But with four concave-convex elements, the image plane is nearly flat; despite the slightly rounded out-of-focus elements. It’s easy to understand a lens performance when the manufacture publishes its formula.
Finally the colors and bokeh are a happy ending to the Yongnuo 100mm f/2 review, and the main reason to recommend it, no matter the focusing issues. This is essentially the “last” near double-Gauss medium-telephoto formula from Canon (I mean, Yongnuo…), before we get the longer 100mm f/2.8 Macro USM and L USM; or the 135mm f/2.8 “soft focus” or f/2 L USM; and also the last long lens with fewer elements (it’s just 8). It’s impressive to see how the YN100F2 photo album is much more colorful than Sigma’s 85mm f/1.4 DG Art HSM (14 elements), both recently tested on the same EOS 5DS camera, on the same days on the same locations in Japan. The out-of-focus background is enhanced by the longer focal length, interesting to isolate your subject and create special effects. It’s the last option before longer telephoto distances, and a good fit for most kits.
The Yongnuo 100mm f/2 is an interesting lens on the low-cost market because once again the Chinese tries to copy an EF lens, but fails to deliver a compelling product, free of issues. If in one hand it’s much more solid than the prior 35mm f/2 and 50mm f/1.8, thanks to the all-internal design that prevents it from misalignments, on the other its bad AF implementation makes it a tough recommendation for all. While I do understand it’s AF + AE appeal (most low-cost lenses can’t even deliver that), the performance is so bad you can actually miss photos, that for sure will be out of focus. So despite the “happy” colorful photo album and the expected optical performance (high center resolution, nice colors from fewer glass elements), I’d carefully recommend it; it might not work with your camera. The US$160 price tag it not that low-cost and it’s an easy decision: a lens for those who can’t afford the real deal, but must opt for this focal length. It works for the daring photographer, but not for faint at heart. Good luck with your purchase and nice shooting!