The Canon EF-M 32mm STM was released in September of 2018, as the third prime lens available from Canon for the EOS M system. It was boasting excellent performance and the fastest lens available in the EOS M system.
Canon when they released the lens had this to say about it;
The EF-M lens is both compact and lightweight, serving as an ideal addition for any photographer shooting with an EOS-M series camera. Entry and enthusiast-level photographers who are passionately seeking to take their photography skills to the next-level will find this lens to be a great addition for portraiture, landscapes or general travel photography.
||STM Stepper motor
|Full time manual
The exterior design is similar to that of other EOS-M lenses, with a standard 61mm diameter and a well-built feel to the housing. The lens mount is metal.
There have been some reports about 43mm filters not fitting on this camera. We personally use 43mm to 55mm step-up filter rings for all our EF-M lenses and had no problems with the 3 different manufacturers of step-up rings.
If you do have a lens that has problems with filters, we suggest that you may have good luck using Teflon tape over the 43mm filter threads.
There is an autofocus distance limiter slider switch located on the side of the lens to assist in focusing quickly to far distances. You choose "full" if you wish to focus down to minimum focus distance, or a faster focus when it's set to .5m to infinity focus. There is a distinct difference when you choose full instead of .5m to infinity. In the full focus setting, you can feel the lens seem to move twice to achieve focus, while the focus is nearly instantaneous when it's on the .5m to infinity setting. If you don't care about minimum focus, it's certainly recommended to have the lens set to .5m to infinity.
The STM motor used in this lens is a lead screw STM motor and offers fast AF.
The manual focus adjustment is focus by wire, with a small manual focus ring at the end of the lens. Focus by wire means that electronically the lens detects if you are spinning the focus wheel and moves the lens accordingly. As you move the wheel faster or slower, will depend on how quickly the focus adjustment occurs. Many people dislike this focus method because it lacks the tactile feel and consistency that you get with mechanically coupled focus rings.
The focus control wheel is large and easily accessible and is well damped.
The EF-M 32mm is a complex design utilizing 14 elements in 8 groups including one aspherical element.
Summary - MTF
The MTF (or Modulation Transfer Function) provides a way to measure lens performance. Atypically this is computer generated based upon models, the lone exception being Zeiss that shows their MTF’s based upon a production lens sample.
For a detailed explanation of MTF and specifically how Canon shows their charts, refer to the article in Canon’s Digital Learning Center here.
Reading MTF Charts
With the Canon EF-M 32mm and newly released EF lenses, Canon has unfortunately settled on a more simpler MTF diagram that only includes wide open performance.
From the MTF we can see that it's supposed to have excellent performance wide open, and we can theorize that the performance improves as you stop down as most lenses do.
From the color samples, we can see that it matches well to the MTF. Performance is excellent from F1.4 onwards and is crisp and sharp across the frame with minimal aberrations. We see a slight softening at 1.4 in the corners, this is nicely cleaned up by F2.0.
Canon’s DPP and some of Canon’s later camera bodies contain DLO, Digital Lens Optimizer, which can be used to correct various aberrations with any of the supported cameras and lens combinations. All the EF-M lenses have DLO “configurations” allowing you to further improve the characteristics of the lens. Using DLO with this EOS-M lens is not really needed, but it still clears up the few aberrations and sharpens up the corners at F1.4.
If you are interested in learning more about DLO, Canon has a DLO mini-website, located at https://global.canon/en/imaging/dlo/
Sharpening for non DLO images is set at USM Strength 2 Fineness 2 and Threshold 1 and for DLO images, USM Strength 1 Fineness 2 Threshold 1 with DLO strength set to 50.
We tested this lens on a full spectrum modified Canon M5. The conversion was done by Kolari Vision, who in our opinion, one of the leading vendors of infrared modified cameras and filters.
Converting your camera allows it to be more sensitive to infrared wavelengths, that are normally reduced by your sensor’s IR/UV cut filter. IR conversion removes that cut filter, and replaces it with an infrared filter, or in the case of full spectrum, clear glass. This allows the camera to be far more sensitive to various wavelengths that normally a camera is not. Because normally cameras are not sensitive to these wavelengths, lenses are also not designed around these wavelengths. Various problems may occur with complex lens designs, including hotspots (a center area of the lens brighter than the peripheral, more noticeable as you stop down the lens) and wavelength smearing which atypically shows up as a loss of resolution in the periphery of the lens. Lenses are also more prone to flare.
Each test is performed using Kolari Vision slim PRO anti-reflective infrared filters, which we find to show the best characteristics and contrast of any filters we have tried. They also have Teflon coated filter threads which we find to be extremely useful when we are swapping filters frequently during testing. While any filters will show an adequate final image, since each photo you are taking with a converted camera has a filter, we recommend using the highest of quality filters that you can afford.
Hot Spot Performance
No hotspots exist with this lens. It's an excellent performer.
This lens is simply wonderful for infrared photography, no signs smearing and resolution is excellent across the frame from F1.4 onwards. For exacting results, you are best to stop down to F2.8.
Sharpening is set to an aggressive USM Strength 6 fineness 6 threshold 2 for non-DLO images and set to USM Strength 4 fineness 5 threshold 2 with DLO images, with DLO strength set to 100.
Vignetting is a slight problem with this lens with just over 2EV of vignetting wide open. By around F2.8 vignetting has decreased to negligible proportions.
This is an excellent lens. It immediately becomes another reason to buy into the EOS M system if you haven't already. It's sharp in the center from wide open and doesn't need to be stopped down significantly to achieve excellent results even in the corners. Even to get absolute sharpness in the corners, it simply requires DLO or to stop down to F2.0.
Infrared performance is the best we have seen in any of the EF-M lenses. Sharpness is maintained, and the lens just works excellent with infrared, with no hot spots that are a common phenomenon on fast primes.
This lens is as close to L quality as you can get with the EF-M system and it's a very reasonable purchase amount of under $500 USD.
We think that any EOS M kit should contain this lens.