Customer Review

197 of 217 people found the following review helpful
4.0 out of 5 stars Small in size but great in features and quality, June 21, 2012
This review is from: Canon EF 40mm f/2.8 STM Lens (Electronics)
Please don't take the Amazon star rating too serious - every lens has its pros and cons that I wouldn't want to squeeze into a single one-dimensional figure...
A quick note about me: I have been into SLR cameras and lenses for more than 20 years - as a hobby in the beginning and professionally later. Maybe because of my technical background I started testing my own lenses quite a while ago. I have a (no longer so) little test lab of my own where I do 6 different image quality tests (after taking a lens out for a while).

Canon's first-ever "pancake" EF lens is a real treat. It's so small that it looks like a 20 mm extension ring rather than a lens and yet it feels solid as a rock and delivers very respectable image quality. It comes with Canon's stepping motor technology (STM) that allows continuous AF during video recording or live-view mode (when used with a hybrid CMOS AF system) and that gives the lens a fast, silent and accurate autofocus performance. The EF 40mm f/2.8 STM is best used for street and travel photography but can also make great portraits or other things. Its maximum aperture of f/2.8 is great but not good enough for available light photography (which requires even lower f-stops i.e. wider apertures) and I would have loved to have an image stabilizer - but of course that would have been very difficult to build into a 2.7" x 0.9" (68 mm x 23 mm) lens.

In regard to image quality the EF 40mm f/2.8 STM is really a high-end lens. The difference is most apparent if you compare it to a zoom lens but also amongst prime lenses of similar focal length the EF 40mm f/2.8 STM is a high performer. The resolution is great straight from f/2.8 both in the image center and corners. If you use a fullframe camera the EF 50mm f/1.4 USM is a little sharper and the EF 50mm f/1.8 II is about as sharp as the EF 40mm f/2.8 STM (compared at the same aperture). But if you shoot with an APS-C camera the EF 40mm f/2.8 STM easily outperforms both of those lenses (apparently it can cope better with the usually higher pixel density of APS-C cameras). It is roughly as sharp as the APS-C-only EF-S 60mm f/2.8 Macro USM (which is more than 3 times its size).

While the EF 40mm f/2.8 STM shows only very little distortion it does express some serious curvature of the focal plane ("field curvature") on a fullframe camera (none on an APS-C cam) but whether that's really visible in an actual image depends a lot on the subject you are shooting and the aperture you are using. Color fringes ("chromatic aberrations") in focused parts of the image ("transverse CA") are noticeable and so are the ones that occur in out-of-focus parts of the image ("axial CA"). On the good side, the nicely shaped aperture creates evenly smooth background blur but if you are bothered by corner shadows ("vignetting") be aware that the EF 40mm f/2.8 STM shows quite intense shadows up to about f/5.6 (with fullframe cameras).

Overall the image quality is quite astonishing for a lens that's as small as the EF 40mm f/2.8 STM and that comes at such a low price tag. This also means that from now on you can always have a decent f/2.8 prime lens with you that virtually needs no space in your camera bag!

Canon set out to create their first pancake lens and they did it the right way - combining great features with an incredibly small size at an acceptable price. I am sure many people will love the lens just for its size and the way it feels but even beyond that the EF 40mm f/2.8 STM has a lot to offer.

A much more detailed review of this lens together with all test shots, sample images and technical data is available on my website LensTests_com.
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Tracked by 4 customers

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Showing 1-10 of 35 posts in this discussion
Initial post: Jun 22, 2012 7:02:13 AM PDT
faremax says:
Sorry, but I can't believe that you would say that 50 1.4 is sharper than 40mm. 50 1.4 is unusable below 2.8 because of excessive softness and lack of contrast and 40mm is tack sharp at 2.8 with great contrast and colors.

In reply to an earlier post on Jun 22, 2012 7:31:29 AM PDT
Well sharpness / resolution is only one of several image quality factors. The 40/2.8 is sharper than the 50/1.4 when used on an APS-C camera but with a fullframe camera it's vice versa. You don't actually have to take my word for it but you can look at the original test shots yourself:

Open the resolution test and shoose the 50/1.4 as an additional lens. Now use your mouse to hover over the lens icons to compare the test shots one-by-one. You'll notice:
- the 50/1.4's siemens star (3) is softer than the 40/2.8's
- the pattern banners (4) however show a lot more detail with the 50/1.4 (check their right end)
- the check board (5) is sharper with the 50/1.4 as well
- I would say that for the big and small lines (6) the 40/2.8 is better than the 50/1.4
- finally the text box (7) is sharper with the 50/1.4

Don't forget that these are lab tests that test a perfectly straight subject with a perfectly aligned camera and lens. In real life photography an aperture of f/1.4 will give you a much narrower depth of field than f/2.8 and thus less sharpness. Of course the out-of-focus blur has little to do with the lens's resolution.

In reply to an earlier post on Jun 22, 2012 7:41:50 AM PDT
faremax says:
I was talking about FF and I don't want to argue too much but here are the links to Canon official MTF charts which clearly shows that 40mm is much better in that regard. I didn't use the lens too much yet but I did a few landscape shots and did not notice field curvature yet.

In reply to an earlier post on Jun 22, 2012 8:00:52 AM PDT
Well Canon's MTF charts have a slightly different approach than the ISO 12233 test shots I do (and Canon's MTF charts are computed rather than measured). Anyway I do agree that the 50/1.4 is not superior in all of the resolution measurements at f/1.4 but it's certainly very useable for apertures wider than f/2.8. Don't get me wrong the 40/2.8 is a great lens but having 2 full f-stops more light hit the sensor can be of great advantage...

Posted on Jun 22, 2012 8:12:46 AM PDT
Last edited by the author on Jun 22, 2012 8:26:16 AM PDT
Java Dude says:
Hi Gil -- a correction for you on the statement that the EF 40 is "Canon's first-ever 'pancake' lens ..." 47 years ago (1965), Canon produced the FLP 38/2.8 for its SLRs. I have owned one. You can find more info and specs at the Canon Museum web site. Quick note about me: I've been into photography for 40 years, and 15 of them as full-time professional.

I'm at the 300 image mark now using the EF 40 on a 5D2, having photographed various real world subjects in sundry conditions and trying to use the full range of aperture settings. I am not experiencing significant CA problems or field curvature problems; certainly nothing the human eye picks up on when viewing the images. The perfomance suggested by your test chart photographs, in these two regards, is not demonstrated in my real world photographs. As for vignetting, I am experiencing about a 1/2 to 1-stop improvement over what your test charts show. Again, all of this on a full frame sensor.

I also concur with commenter faremax regarding the sharpness comparison with the 50/1.4 at the f/2.8 setting on full frame sensors. The EF 40 is sharper, and the contrast much better. But yes, I agree with you that 50/1.4 images taken at apertures larger than f/2.8 are certainly usable.

I appreciate photos of lens test charts to a degree. They can provide clues for me to look for evidence in real world photos. Then I am able to evaluate whether there is practical significance to what a chart shows. It's good to know where the boundaries of performance are for your lenses.

Happy snaps!

In reply to an earlier post on Jun 22, 2012 8:37:20 AM PDT
Hi Rick, thanks for your correction - I wasn't aware of the FLP pancake lens and I guess neither was the Canon PR guy that wrote the German press release for the lens (which is where I got the "first-ever" from):

I totally agree with you that test charts don't really tell you how good a real image will look that's taken of a real subject and the difference in sharpness between the two lenses we are discussing here is really minor for all practical aspects.


In reply to an earlier post on Jun 22, 2012 12:39:20 PM PDT
faremax says:
Gil, have you tried doing side-by-side with 35/2?

In reply to an earlier post on Jun 22, 2012 12:52:12 PM PDT
No, I haven't - not yet anyway...
Do you use the 35/2? Do you like it?

In reply to an earlier post on Jun 22, 2012 1:01:38 PM PDT
faremax says:
I've used it a few times but never owned it. From what I remember it was not a bad lens. Pretty sharp. I was thinking about buying it or the Voigtlander 40mm f/2 when suddenly Canon announced 40mm pancake. I liked Canon's specs so i decided to give it a try and instantly fell in love with it :) Still can't believe the IQ of that little lens.

In reply to an earlier post on Jun 22, 2012 1:10:12 PM PDT
Yes, I also find the 40's build quality really amazing. And in comparison with the 35/2's micro motor the 40's STM is a real charm...
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