For most photographers fisheye lenses are not the most popular/useful lenses because of the extreme barrel distortion. For action sports photographers, fisheye lenses are a necessity.The Canon EF 15mm f/2.8 Fisheye has been around since the 80's, with the same simple design. It is really popular amongst Skateboard and Snowboard action photographers, and also widely used for underwater applications. In this fisheye review we are not going to go in to details and test charts, instead, we are going to review it as professionals using it on a daily basis out in the field.It is a pretty small and really light lens, so it's not a problem if you have to hold it in your hands for a long time. The design is not amazing, but that's because it's a well built lens. The front element is rather large and you can’t thread a filter on it. It has a nice metal lens cap but make sure you put a rubber band or some kind of strap around it, especially if you are going to be riding a bike or skiing with it. The cap tends to come off and the edge of the cap can hit the front glass element and scratch it. It happens to us all the time so take our advice seriously.The lens provides a 180 degree field of view on a full frame body and you can barely notice it is a fisheye on a camera with a cropped sensor. On the 1D( that has 1.3 crop factor) we would call it a “mild” fisheye. You can definitely see the distortion but if you keep the horizon line straight it almost looks like a really wide angle lens. We use it as a wide angle lens in situations where the 16-35mm lens is just not quite wide enough. You can always correct some of the distortion later in photoshop!When it comes to resolution, you will be amazed! Even at f/2.8 the lens performs really well. Center sharpness is great and corner sharpness is very good. When stopped down to f/4.0 or more you get amazingly sharp images. Chromatic aberration is often a problem with wide angle lenses, but due to it’s simple desigh it is extremely well controlled, especially when compared to any 3rd party fisheye lenses.The 15mm Fisheye has 5 aperture blades that results in to a sun star with 10 spikes. This makes for great sun-starred images. Flare is definitely well managed too.Overall this is a great and well-made lens that is very affordable and definitely worth the investment. Not to mention all the crazy compositions you can easily come up with when using it. If you have experience with this lens, don’t hesitate to share your opinion with us. If you don't, and are buying one, check out this article for tips on shooting with a fisheye.