Canon 24mm STM review.
I love “Pancake” lenses because they don’t take too much space and don’t add a significant amount of weight in my camera bag ! A Pancake lens needs to have some compromise optically to be so small, so you can’t have it all for such a small lens and low price. Usually they are slower lenses, it’s inevitable if you want a pancake lens, if you want a fast lens it will be bigger and heavier. I’ve owned some Pancake lenses over the years, very good ones like the Fuji XF 27mm and some not so good like the Sony E-mount 16mm. Pentax makes some great Pancake lenses in the DA Limited series, currently I own the Pentax DA 40mm/2.8 XS which is a derivate of the Pentax DA 40mm/2.8 Limited but even smaller …. it’s the smallest lens available for an APS-C camera.
Canon finally came-up with two Pancake lenses, the 24mm STM and 40mm STM. For me the 24mm was more interesting since I already had the Pentax DA 40mm XS in my bag and also because of the close focusing ability of the 24mm which is interesting for it’s focal length. So I bought one last fall (2015) and I now have enough experience with it to share my thoughts with you.
The built quality is not as good as the Pentax Limited lenses which are all metal construction, even the front lens cap is made of metal. But for a plastic lens at that price it’s quite good, especially if you compare it to Canon’s 50mm/1.8 or the 18-55mm kit lenses !

Here are my two Pancake lenses that I have in my camera bag: on the left side the Pentax DA 40mm/2.8 XS and on the right side the Canon 24mm/2.8 STM.

This photo was taken the next morning I bought the Canon 24mm. It was -4°C and all the vegetation was covered with a thick layer of frost. Taken at f/11 on a tripod.

This photo of an old canal was taken on a cold morning, I used a Polarizer to obtain a longer exposure. Taken with the Canon 24mm at f/11 on a tripod.

I arrived at the Rouge River in Grenville before sunrise in late October, suddenly close to sunrise the clouds behind me took a pink/orange color that casted that warm glow on the landscape. Taken with my 7D and 24mm STM, ISO 100, 25 sec. at f/11, tripod.
The IQ of the Canon 24mm STM is quite good at normal distances and also at the closer focusing distances but some distortion can be seen. It’s not as good as my Pentax DA 40mm XS but it’s not the same focal length, maybe I should try a head to head battle between my Pentax and the Canon 40mm STM ( would have to buy one first) !!! So, in term of sharpness I would rate it as very good.

It was useful at the ZOO to take close-ups of more accessible animals.

This is a crop of the previous shot after processing and some sharpening, it was taken at 1/640 sec. at f/6.3, ISO 400.

If you look carefully you can see that the Canon 24mm STM still produce some CA along the edge of the ice even when stopped down to f/11. But it’s easily removed in LR.

Another shot taken at sunrise along a frozen river, at f/11.

A more abstract shot, this is a rock covered with snow. Taken at f/11
I find the new STM AF system “strange”, it take some times to get used to it, the lens tend to hunt in some situations. I’m using it mainly in LV and on a tripod so even if the AF is not top notch I don’t mind. Keep in mind that i’m using it on a 7D, so a more modern 70D or the new 80D certainly are better cameras to take advantage of the STM motor.

With this photo I was able to test the close focusing ability of the Canon 24mm. The Bokeh at f/7.1 is not too bad.

Again, the close focusing ability of the Canon 24mm was useful to get the composition I wanted. I usually don’t place my subject in the center but this time it was what worked the best to my eye.

A small river in a forested area, I used a Polarizer to remove the reflection off the water’s surface. Taken at f/11.
What I like about that lens is when i use it for “close-up” shots, it produces a feeling of being more intimate with the subject compared if I had used a longer lens like a 100mm Macro lens which produce a more compressed look due to being a telephoto lens. The minimum focusing distance of 0.16 meter gives you a maximum magnification of 0.27, which is very good for a 24mm lens. Most of the 24mm lenses don’t focus close enough, i think manufacturers could make an effort to design more lenses with a closer minimum focusing distance. Tamron new SP 35mm/1.8 VC and 45mm/1.8 VC are very good examples of lenses that focus closer than the competition and really interest me.

This photo of Cedar leaves was taken on a cold Canadian morning (-28°C and with the wind chill factor it was -38°C). Another good example why I really like that lens for more intimate shots. Taken at f/11.

A leaf on a road covered with ice. This is the kind of subject that I really like to photograph and the 24mm STM is a very good choice to render the perspective I want. Taken at f/11 on a tripod.

Ice fishing cabins in B&W, taken at f/10.

Freezing rain was still falling when I took that shot of a frozen Blueberry shrub with a rock in the background. I converted it to B&W and processed it until it looked how I wanted. I was able to handhold it at 1/100 sec. at f/11, ISO 200
Update on CA
I wanted to update my review about the CA that I didn’t talked much about. It might not be evident on regular subjects or even on more prone subjects like high contrast but during this winter I was able to find some CA on ice and snow shots. Sure it’s not visible at regular viewing but when zooming in you will see it but it’s easy to correct in LR.
As you can see there is more to a lens than sharpness, sure I like very sharp lenses but when buying a lens i also look at the lens in general, not just how much details it can resolve. Usually i prefer a lens that will focus closer to a lens that is the sharpest lens on earth but can’t focus close enough for my needs. It’s because of my shooting style, it will probably be different for another photographer.
Conclusion
The more I use that lens on a crop sensor camera the more I realize that I like shooting at that focal length. It’s a very useful FOV and especially with the closer focusing of the 24mm STM it makes a great all around lens. I now see more and more potential photos as I become more familiar with it. At one moment it’s a “Wide angle” lens and then it becomes a Close-up lens.
Canon came out with a very good lens with some compromises (CA and distorsion), but because of it’s small size, very good IQ and minimum focusing distance, it now have a place in my camera bag with my other Pancake lens, the Pentax DA 40mm XS, especially since I paid less than 300$ Canadian for 2 lenses ! I can’t wait to use it for photographing Frogs up-close next summer and I think it will do a great job even if there is no IS incorporated. The only thing i’m missing now to take full advantage of it’s small size …… is a Canon SL1 !

This shot was taken around sunrise along a frozen river. Taken at f/13.