YONGNUO YONGNUO YN42.5mm F1.7M II Auto Focus Fixed Prime Review

If you're shooting on a Micro Four Thirds camera and want a cheap, fast prime lens for portraits, the Yongnuo 42.5mm F1.7M II is probably on your radar. It's a compact, lightweight lens that gives you an 85mm equivalent field of view, which is a classic portrait focal length. For around $138, you get a bright f/1.7 aperture in a package that's easy to toss in any bag. People often search for budget portrait lenses for MFT, and this one fits the bill, especially if you're using a Panasonic G series or an Olympus PEN camera.

The f/1.7 aperture is the star here. It lets in a lot of light, which is great for indoor shots or evening portraits without a flash. The lens scores in the 71st percentile for bokeh, so you can expect nice, smooth background blur when you shoot wide open. Its autofocus lands in the 46th percentile, which means it's fine for casual or slower-paced portrait work, but don't expect lightning-fast tracking for sports or hyperactive kids. The 91st percentile macro score is a nice surprise; with a minimum focus distance of just 30cm, it can double as a decent close-up lens for details.

At $138, the value proposition is simple: you're paying for the aperture and focal length, not for perfect optics or features. You're getting a fast portrait lens for less than half the price of most first-party options. If your main goal is to get that blurred background look on a tight budget, it delivers. Just know you're making some trade-offs in optical performance and features to hit that price point.

Let's name some names. The Viltrox 35mm F1.7 is a direct competitor in the same price range, offering a slightly wider field of view (70mm equivalent). It's a toss-up depending on your preferred framing. The Panasonic 14-140mm f/3.5-5.6 is the opposite: a super-versatile zoom, but much slower, meaning worse low-light performance and less background blur. If you have more budget, the Panasonic Leica 42.5mm F1.2 is the premium version of this focal length, with far better optics and build, but it costs several times more. The Yongnuo sits in a sweet spot for budget-conscious shooters who want a dedicated, fast portrait lens and are okay with its limitations.

So, should you buy it? If you're new to MFT, want to try portrait photography without a big investment, and your camera is on the compatibility list, this lens is a fun, low-risk way to do it. It's good for portraits and close-ups, as the scores show. But if you need sharp corner-to-corner image quality, fast autofocus for action, or a lens you can use for everything, you should look elsewhere. This is a specialist tool for a specific job, and it does that job well enough for the price.