Xiaomi Yi 42.5mm F1.8 Review

Back in 2016, Xiaomi's sub company, Xiaoyi launched their first Micro Four Thirds products, the Yi M1 (with a kit lens) as well as an accompanying Yi 42.5mm F1.8. I found the Yi 42.5mm F1.8, which is a Micro Four Thirds AF lens selling for only RM270/USD70 online (Shopee Malaysia), so I thought what could possibly go wrong? This is the cheapest AF lens for Micro Four Thirds, and I was just so curious to find out of the lens is any good! Pairing the Yi 42.5mm F1.8 with my own Olympus OM-D E-M5 Mark III, I roamed the streets and got myself some shutter therapy too. 

As usual, I have a video version, if you prefer to watch a video over reading text/article format, then go here (click). 

Size comparison between Yi 42.5mm F1.8 (left) vs Olympus 45mm F1.8 (right)

Disclaimer: I am not affiliated with Xiaomi, they did not send me a review sample, or asked me to do anything. I bought the Yi 42.5mm F1.8 lens with my own money and this is a fully independent review. This is also a non-technical review and I shall share my experience as a professional photographer, based on many images I have taken with the lens in real life conditions. My opinion is subjective. 

We are not lack of options when it comes to 85mm equivalent focal length, or close to that, currently the two popular prime lenses are Olympus M.Zuiko 45mm F1.8, and Panasonic Lumix 42.5mm F1.7. However, both lenses also cost significantly more, about at least 4-5 times the price of what I paid for the Yi 42.5mm F1.8. It was interesting to see what the compromises are, how they made it so cheap and is the lens performance (optical design, flaw control, etc) as good as the Panasonic or Olympus' offering? I don't have the Panasonic lens, but I have been using the Olympus 45mm F1.8 for many, many years, and it is my favourite lens for both my commercial jobs as well as personal shoots. 

WHO IS THIS LENS FOR?

Medium telephoto lens (50-100mm equivalent focal lengths) is my favourite, I use this most of the time for most of my shoots. The longer focal length (85mm equivalent in this case) mitigates ugly perspective distortion when shooting close up to subjects, especially humans, without over exaggerating certain body features. If wide angle lenses were used, you would see faces being stretched wider than what is perceived natural, or the head and nose appearing too large in proportion against the body, or legs being shortened. These problems are less obvious using a longer lens. Also, using a longer lens means there is less background to deal with, which makes this a good lens for portrait photography. Having a longer lens with F1.8 bright aperture allows good separation from the background, rendering shallow depth of field. 

BUILD & HANDLING

The Yi 42.5mm lens is made of entirely plastic, and it does feel cheap holding in hand. The body of the lens is plastic, the lens mount is also plastic, which does not really inspire much confidence. It is a cheap lens after all, and using the lens reminds you of that. The size of Yi 42.5mm is surprisingly larger than expected, it is about 30% larger than Olympus 45mm F1.8. For a Micro Four Thirds prime lens, I thought they could have downsized the lens a little further. Nevertheless I had no issue handling the lens despite its larger size, I coupled the lens with my own Olympus OM-D E-M5 Mark III for my shooting sessions. 

It is important to note that there is no way to do manual focusing with Yi 42.5mm lens. There is a ring around the lens that appears to look like a manual focusing ring, but that is not a manual focusing ring, it was purely cosmetic, and there is no way to turn the ring or do anything with it. They should just get rid of the ring if it serves no purpose, instead of confusing people. There is also a macro function switch on the lens, activating the macro mode which we will explore more in depth a little bit later. 

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LENS SHARPNESS

According to Xiaomi's official product specifications, the Yi 42.5mm F1.8 lens is constructed of 6 elements in 6 groups, which is quite a simplistic design for a Micro Four Thirds lens. Testing the lens in various real life environment, I must say that I am quite satisfied with the lens sharpness. The Yi 42.5mm is able to resolve plenty of fine details and good contrast. The lens consistently produces sharp images, even when shot at wide open aperture of F1.8, and I won't hesitate to use F1.8 for most of my shots with good results. The sharpness is also shown to be quite good at the corners and edges of the frame. This is truly impressive, coming from such a budget lens, and I'd say most people won't be disappointed with the lens sharpness of Yi 42.5mm. 

TECHNICAL FLAW CONTROL

When shot at wide open F1.8 against bright or harsh contrast conditions, the lens does exhibit some traces of purple fringing, but I don't see this as a huge problem, it can be easily corrected in post-processing software. I did not observe any corner softness or distortion, both may be compensated by software. Lens flare is very well controlled, even shooting against direct source of light, without the use of lens hood. Generally, I find that the lens is doing quite well when it comes to overall lens flaw controls, and certainly miles ahead of what the typical manual focusing lenses at such price range can offer. 

AUTOFOCUS

The great thing about Yi 42.5mm lens is the native ability to AF, which makes this lens a lot more valuable than other similar alternatives - cheap manual focus lenses. Not only is this lens optically superior (less CA, good sharpness wide open, no distortion, good flare control), the fact that it can perform AF places this lens well above those manual lenses in terms of shooting hit-rate - nailing moments. The AF is not the fastest among all available Micro Four Thirds lenses, it isn't as fast as Olympus 45mm F1.8, maybe slower just by a fraction but it is definitely noticeable. Having said that, the AF still performed admirably well, speedy and reliable enough for me to grab critical moments when I was shooting on the street. 

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Crop from previous image showing Purple Fringing

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Crop from previous image showing corner softness. Left F1.8, vs right F4

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Lens Flare Sample

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Starburst effect sample

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COMPARISON WITH OLYMPUS 45MM F1.8

I am sure the biggest question is - how does the Yi 42.5mm F1.8 compare to Olympus 45mm F1.8? Olympus 45mm F1.8 is a great lens, I made no secret that I love that lens, and still think it is a must have lens if you shoot with Micro Four Thirds. However, Yi 42.5mm presents an interesting alternative. 

The Yi 42.5mm is larger in build, and I like that Olympus managed so shave off a lot more size, making the 45mm F1.8 truly compact, and much tinier. The Yi 42.5mm lens takes 49mm filters, while the Olympus 45mm takes only 37mm filters, that shows much much difference in size between these two lenses. The Olympus lens is also better built, feeling denser in hand, having metal lens mount, and holding in hand, the lens feels more premium and robust in comparison to cheaper plasticky feel of the Yi 42.5mm lens. I'd say, in this case, you get what you pay for, Olympus cuts less corners in making a lens, looking at how better built their 45mm F1.8 is. 

In terms of sharpness, both lenses are very close. In fact, if you put images shot with Olympus vs Yi lenses side by side, without pixel peeping I won't be able to tell apart which was taken with which lens. The sharpness of Yi 42.5mm generally comes very close to what the Olympus 45mm F1.8 can do, and that is truly amazing coming from a super budget lens from Xiaomi. However, if I have to pick a winner between the two, the Olympus 45mm F1.8 does have slightly better sharpness overall and more refined micro contrast. After much pixel-peeping I conclude that the Olympus images have better "bite" in them, but the slight advantage is not easily discernible, and honestly, quite negligible, considering the huge price gap between the two lenses. 

Bokeh quality is a separate issue altogether. The out of focus rendering of Olympus 45mm F1.8 is superior. The bokeh balls from Olympus 45mm is rounder and fuller, looking more pleasing. The Yi 42.5mm produces bokeh balls that are out of shape, looking stretched and more ovul, which may appear less attractive to most people. Olympus 45mm F1.8 also creates less "onion ring" effect in the bokeh balls. I don't think this is a deal-breaker, but it is worth noting that Olympus does render better bokeh. 

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Yi 42.5mm (left) vs Olympus 45mm (right)

Olympus 45mm at F1.8 (left) vs Yi 42.5mm at F1.8 (right

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Olympus Bokeh

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Yi Bokeh

Bokeh comparison, Olympus (left) vs Yi (right)

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MACRO MODE

Perhaps the only big advantage that the Yi 42.5mm F1.8 lens has over Olympus 45mm F1.8, is a macro mode. The macro can be activated via a dedicated switch on the lens itself, allowing you to go much closer to the subject and amplify the overall magnification of the subject. Do take note that once the macro function is activated, the widest aperture is stopped down to F3.5 (instead of F1.8 during non-macro shooting) and the AF motor starts to buzz a little noisier. The overall focusing operation is also slower in the macro mode. 

The difference between the largest magnification provided by macro mode of the Yi 42.5mm lens, vs closest focusing by Olympus 45mm F1.8 lens is massive. While the Yi 42.5mm is not a true macro lens, if you are not doing anything too serious about macro (if you are, why don't you have a macro lens), the Yi 42.5mm can give you much better close up shots. This can effectively open up a lot more shooting possibilities, and I did wish at times that I can go much closer with my own Olympus 45mm F1.8. If you need a reason to choose the Yi 42.5mm over the Olympus 45mm, besides the price difference of course, is the macro function. 

After all the discussion, so, which lens is better? Olympus or Yi?

Well, there is no straightforward answer. 

If you shoot with Olympus, and if you are not cash-constrained, you don't mind to spend a little more, the Olympus M.Zuiko 45mm F1.8 is the better choice, no doubt. You get what you pay for, the build quality on Olympus is vastly superior than the Yi. Being smaller means you can match the lens with smaller camera bodies better, taking advantage of the truly compact Micro Four Thirds system. Image quality wise, the Olympus 45mm F1.8 is also better overall, rendering impressive sharpness with better bokeh. 

On the other hand, if you don't have the funds to spare, and are not willing to spend too much on lenses, then then Yi 42.5mm offers an interesting alternative. At a fraction of the cost of Olympus 45mm, the Yi 42.5mm (at only USD70) offers image quality coming very close to what the Olympus can do, and it does have AF capability, which makes this lens usable in wider shooting scenarios than manual focus lens options. While there is some compromise when it comes to larger build size, and poorer construction, Yi has a neat trick up it's sleeves - the macro mode which makes this lens more versatile if you want to some close-up shooting. 

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Olympus 45mm maximum magnification

Yi 42.5mm maximum magnification in Macro Mode

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That's all I have to share about my experience shooting with the Yi 42.5mm F1.8, I sure hope you have enjoyed the images (mostly restricted to street photography now, can't do anything more adventurous due to the on-going pandemic and movement restrictions). I also hope you have found my sharing useful. If you have owned the Yi 42.5mm lens please share your own experience using the lens, I'd love your thoughts. 

I do have a few more interesting products to try out, and review. I can't wait to shoot more. 

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