Canon 17-40mm F4 L

The 17-40mm F4 L has been a part of my arsenal for about two years now and I thought I would share my thoughts on its range and capabilities.

When I purchased this lens, I was using the Rebel T3i and wanted a better lens to replace the 18-55 kit lens it came with. Having already purchased a 50mm 1.4, the 17-40mm filled exactly the range I needed to replace. The other option was the 18-55 f2.8 lens, but it was a cropped sensor lens and I was thinking about moving to full frame. So I purchased the 17-40 used.

One of the main benefits to this lens compared to the one it was replacing was the constant f4 aperture. The 18-55 has a variable f3.5 - 5.6 which made shooting frustrating in manual mode as you were constantly having to compensate whenever zooming in or out. This consistency made shooting much easier. Being that it is an f4 lens, it is still relatively dark compared to the f2.8 16-35mm lens Canon offers. However, for the type of shooting I do, there is generally plenty of light to work with. It is also much less expensive.

Using this lens on a crop sensor gives you roughly a 28mm - 64mm equivalent making it an ideal walking around lens. Soon after I bought this lens, I swapped my camera for a 6D that came with a 24-105mm f4. This was allowed me to use the full angle of view provided by the 17-40mm and it is very wide. The irony is that the 24-105mm range is more what I'm comfortable with and so I ended up using that one much more than the 17-40mm. But this lens still has very practical application, and when I need that extra push, I'm always happy to have this lens in my kit.

Optically, this lens is fairly sharp. Wide open and stopped down the image comes out plenty sharp, especially in the center. It is not without defects however. At 17mm the lens has pretty severe distortion, which is to be expected from an extreme wide angle. At 40mm the lens behave fairly normally. There are occasionally aberrations as well as most focal lengths, but none so severe that they cannot be removed in post processing. For me, all this was expected and so I took it as it was. 

Weather sealing is an added bonus to the already sturdy lens. It is heavy but not so heavy that it is a burden to carry around. The focus and zoom rings respond nicely, and when facing down it does't seem to slip out of focus or change focal lengths. The 24-105 definitely has this problem. Another cool feature is that the front of the lens doesn't extend when zooming or focussing. The zoom isn't internal per say, but the barrel of the lens covers this motion, so it does't change size when zooming or focussing making it compact and easy to travel with. 

On the front of the lens, threads for 77mm filters are permitted which is standard, but on the rear of the lens, there is a slot for gel style filters. So you could put a UV filter on the back, and a polarizer on the front so you don't have to stack filters potentially having them show up in images at the 17mm setting. I've never used it, but it might come in handy.

Overall, I really like the lens. It works well and tight spaces, as well as just walking around. It is a sturdy wide angle that offers a good range for a secondary lens. If you are someone who shoots medium to wide, this is probably a good lens for you. However if you are someone who shoots mostly extreme wide, finding a good 14mm or similar focal length may be a better choice. I wouldn't necessarily call this lens a budget lens, but if you can find a good used one, or don't need the extra stop of light the 16-35mm offers, it falls in that middle price range. For the quality and price, its worth it to me even if you have to do a little editing to clean up some distortions or aberrations. 

Thanks for reading!