This wide angle conversion boost lens works spot on perfect with both my action 4 and action 5 cameras. It provides a super wide perspective which comes in super handy when framing certain activities. The glass and build quality is top notch. Super durable and a good value for the price.

this lens has excellent functionality for getting a wider shot and the quality of the glass is very clear with no distortion. the ease of use for screwing it onto the camera is simple and it is a solid value for money for an add on lens. the durability of the metal housing feels reliable for daily photography. it fits perfectly and the photos look much more professional now. it is a well made and practical accessory for any camera kit

The materials of the lens feel high quality. It is substantially larger than the stock lens of my Osmo Action 4. Installation is a breeze just unscrew the stock lens and screw this one in its place. As expected it significantly increases the field of view making it an excellent option landscapes or large group pics.

This wide-angle lens is a really solid add-on for the Osmo Action. It screws on cleanly without any wobble, and the 185° field of view makes a huge difference when you want to capture more of the scene—especially in tight spaces or when filming action shots up close. The glass looks well-coated and resists glare better than I expected for an accessory lens.Image quality stays sharp across most of the frame, and I didn’t notice any weird color shifts or distortion beyond what you'd naturally expect from such a wide lens. For the price

This adds the one thing I wish the Osmo Action had from the start, a wider FOV. This brings it up to 185deg as opposed to the 155 stock lens. This is a big jump in FOV. This will make action shots look much better. It fits and functions on the Action 4 perfectly. Seems well made and should be durable enough. It comes with a silicone carrying case, that half of it doubles as a lens cover, which you do need with this lens as its a LOT more glass sticking out the front. It is a bit heavy, so if weight is a concern, this may not be for you.

The K&F Nano X Filter gives a slightly wider view. But do expect corners and edges to be a bit more distorted and blurry. Albeit, I like the look but others may find it annoying for their footage. You’d basically have to try it to see if it’s something that you like. No difference in colors. Built solid.

Right out of the box, the K&F Concept wide-angle lens feels premium and well-built. The metal housing has a solid, precise finish, and the optical glass is crystal clear—no signs of distortion or cheap coatings. It screws directly onto the DJI Osmo Action 5 Pro or Action 4 with a snug, secure fit, just like the original lens, so there’s no wobble or alignment issues even during high-motion activities.Once attached, the 185° field of view is immediately noticeable. It dramatically expands the frame, capturing more of the surroundings and giving every shot that immersive, cinematic feel—especially great for biking, surfing, or travel vlogs. The image quality stays sharp edge to edge, with minimal fisheye distortion and excellent color clarity thanks to the 28-layer nano coating. Reflections and glare are impressively controlled, even in bright outdoor light.What really stands out is how easy it is to use—just screw it on and shoot. No adapters, no adjustments, and it doesn’t interfere with ND filters or other accessories. The nano-coated glass also repels water and fingerprints, making it quick to clean after outdoor sessions.The only caveat is that it’s not waterproof, so it’s best avoided for underwater shots or heavy rain.Overall, this lens is a top-tier upgrade for Osmo Action users who want to expand their creative range. It’s ideal for adventurers, vloggers, and content creators who want that extra-wide perspective without sacrificing image quality or ease of use.

I ordered this wide angle lens adapter purely out of curiosity. I have the Osmo Action 4 & 5, and find occasional use for them when travelling. Since I can crop in post processing I thought perhaps adding this would mean I get more footage per frame and can crop afterwards. The reality is, since I'm not really in need of fisheye footage, I may not use this as much as others.The filter comes in a simple rubber 'box' which strays from the plastic box you would normally receive. It makes sense as this filter is quite thick vs the ND/CPL ones.It's easy to fit, just screw it on, and easy to use because there's no modifications like with a CPL. It's a good quality lens with no immediate concerns regarding the captured footage, but I can see issues with the fish eye aspect, which will need moderate correcting.For some reason K&F seem interested in storage capacity for this review which I will say, there is none - obviously. Storage capacity of my camera is fine though.This is perhaps a niche adapter but I would say is good value for money for those who can use it.

1.) First impression/Technical details

The boost lens for the Osmo Action 4 & 5 Pro makes a very high-quality impression even when unpacked! The metal frame looks neatly finished, the optical glass is clear and free of streaks, and the 28-layer nano coating underlines the professional standard. The thread mount is exactly the same as the original Osmo Action lens, which ensures a secure fit.

2.) Practice test

In use, the 185° ultra-wide angle is particularly impressive due to the significantly expanded image section. Landscapes, urban scenes and action shots appear noticeably more open and dynamic. According to the manufacturer, the horizontal image area is expanded by around 26% and the vertical image area by around 24%, which is clearly visible in practice. (See video)
The image quality remains relatively stable:
Colors look natural, contrast and sharpness remain at a high level, and annoying reflections are effectively reduced thanks to the multi-coating. It is important to activate the camera's wide-angle mode in order to exploit its full potential. Threaded assembly is quick and fits securely even when moving.

The lens should not be waterproof and the slight distortions on the edges should not be ignored, but don't forget: It is a creative lens! :)

3.) My personal conclusion:

From a content creator's perspective, this wide-angle lens is a real addition to the DJI Osmo Action 4 & 5. It significantly expands the creative scope without sacrificing image quality too much and is ideal for vlogs, travel and action shots. The high-quality workmanship and clean optical performance justify the price.

The only minor limitation point remains the lack of waterproofness, which must be taken into account when shooting underwater. 

Overall, however, the benefits clearly outweigh them, which is why I am making a clear purchase recommendation here.

Good quality. I’m happy.