Tuesday, August 21, 2012

REVIEW: Canon EF 40mm f/2.8 STM–Pancake Schmancake?


Canon EF 40mm f/2.8 STM Pancake Lens
Buy now from Adorama or B&H

When Canon announced its new 40mm pancake lens speculation quickly picked up about Canon entering into the mirrorless market (which materialized with the EOS M). However, detailed observers quickly noticed that this was an EF lens – not an EF-S or the new EF-M style lens. What this means is that this lens can be used on both full-frame as well as cropped sensor cameras by Canon.

Now why would Canon release a tiny lens like this for a big bulky full-frame camera? Well that’s where the other new moniker on this lens comes into play – the STM designation. STM stands for “Stepping Motor” but what this really means is that it’s a new motor mechanism that is quieter and seemingly faster than Canon’s Ultrasonic Motor (USM) found on most of its lenses. The reason why they did this is that when you do video on a DSLR those big USM lenses would make noise that was audible in the videos audio track, so when Canon added full-time continuous autofocus to the Canon T4i they needed a lens that could keep up with the performance demands without making too much noise.

Crunchy Pancakes?

Now a logical person would naturally think that because of STM and the tiny size of this lens that it would be super quiet right? Well oddly enough the unit I tested was audible from an arms length away while its much larger cousin – the EFS 18-135mm IS STM (see here) – is actually is near impossible to hear at a hand length away. So in the noise department this lens left me rather disappointed. Granted, it did outperform even nice L lenses with USM in terms of output noise, but I wouldn’t call this a super quiet lens.

Is this lens as sharp as everyone says it is?

It’s been a tough summer for bloggers so I suppose many are looking for the next hot thing to boost their incomes, but I’ve got a good day job that pays the bills so I’m here to tell you the truth about this lens. The truth that I experienced with this lens is that it’s about what you’d expect for a $199 prime lens – it’s super sharp in the center, but the quality quickly fades from there as you can see in this blur index from my favorite lens analysis site – slrgear.com:

Canon EF 40mm f/2.8 STM Pancake Lens Blur Index
Full details at http://slrgear.com/reviews/showproduct.php/product/1523/cat/10

If you aren’t used to reading one of these things then let me point out that 0 is pink which is the sharpest you can get and the scale on the right goes up from there in color to the most extreme blur of 12. Blur isn’t all bad because it can be desirable in a portrait lens, but better lenses typically have great edge to edge sharpness once you get them to f/8. With that fact in mind, you’ll see that this lens is really sharp in the center but quickly fades into a less sharp area and then gets inconsistent at the edges. This is common for cheaper or older designed lenses, and given the price of this lens isn’t that bad.

What this blur index tells me is that this is a better portrait lens than it is a landscape lens (where you typically want good edge sharpness). Now compare that to Canon’s 24-105mm f/4L IS USM lens at f/8 (and 35mm because there’s no 40mm mark on the lens):

Canon EF 24-105mm f/4L IS USM Blur Index
Full details at http://slrgear.com/reviews/showproduct.php/product/145/cat/11

What this tells me is that the 40mm pancake lens is going to be sharper in the dead center but the 24-105mm is going to be better at the edges which you can clearly see in these bookshelf test images:

Canon EOS 5D Mark III, 40mm STM, f/8 @40 mm, 13s, ISO 100 (Click for original)
Notice how the center is super sharp, but the white text on the pea green
book on the far right is soft compared to the image below?

Canon EOS 5D Mark III, 24-105mm, f/8 @40 mm, 13s, ISO 100 (Click for original)
Notice how the center is softer, but the white text on the pea green
book on the far right is much sharper compared to the image above?

You have to view both images at full-size and pixel peep to see the differences, but you’ll notice the blur index is pretty accurate. The center of the image is sharper for the pancake lens and the edge is sharper for the 24-105mm just like the blur index indicates.

Now to be fair the pancake lens does a good job considering the fact that it’s 1/5th the cost of the 24-105mm and it’s sharper in the center. Perhaps this is what all of the fuss is about, but honestly this lens just didn’t impress me in real life. It’s build quality reminded me more of the super cheap nifty fifty than it’s better built 50mm f/1.4 sibling. This on top of the aforementioned noise (something also found with the nifty fifty) made less than impressed with this lens right from the start.

You can’t always judge a book by its cover so I figured I must be missing something about so I took it out and shot hundreds of shots with it. I expected to be dazzled like I was when I first used the 50mm f/1.4, but the real result was that I was left with a lot of soft shots that failed to impress. Of course there were some successes like the flower shot at the beginning of this article, but they were few and far between. When using it on the camera it was made for – the Canon T4i – I was even more disappointed. As you can see below:

Canon EOS REBEL T4i, 40mm STM, f/8 @ 40 mm,13s, ISO 100
Click for a full-size original


You can use the data from the blur index here and on SLRGear.com to judge for yourself, but overall this lens left me underwhelmed. Sure, it’d be a decent lens if you’re going to shoot a portrait with them in the center like this mastiff puppy:

Canon EOS REBEL T4i, 40mm STM, f/3.2 @40 mm, 1/160, ISO 100

However, you typically want a longer lens for portraits (I prefer at least 100mm and ideally 200mm+). This makes it too short for portraits, too noisy for video, too slow for sports. Honestly, I’m pretty unimpressed!

In real life I found that this lens performed so poorly that I most often preferred shots with the EF-S 18-135mm f/3.5-5.6 IS STM (like this or this) instead.

The other STM lens – EF-S 18-135mm f/3.5-5.6 IS STM

There’s actually several STM lenses, but the EF-S 18-135mm f/3.5-5.6 IS STM is one you can get as part of the kit for the T4i. As you can see from the blur index below, this lens is closer to the L than the pancake lens:

Canon EF-S 18-135mm STM Blur Index
Full details at http://slrgear.com/reviews/showproduct.php/product/1522/cat/11

Of course, the blur index doesn’t show you the reality that the 18-135mm has much more chromatic aberrations than the pancake or 24-105mm lens. It also doesn’t show you that the images from the pancake lens didn’t have the same warmth I’d get from 18-135 STM. However, this zoom lens actually impressed me much more because it’s a zoom that is quieter and performs quite well as a travel lens (especially with landscapes).

For video there was no comparison as the 18-135 STM significantly outperformed the 40mm 2.8 pancake by a significant margin.

The Bottom Line

If money is burning a hole in your pocket and you think the 40mm STM is for you, then buy it. However I’d caution you to open it carefully, treat it gingerly and save the box as I suspect that once the thrill wears off many will quickly become bored with this limited use lens. I’d suggest considering the 50mm f/1.4, 24-105mm or Sigma 85mm  as better alternatives. If you’ve gotta get a STM lens, then go for the T4i kit.

Ordering Information

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I borrowed the 40mm STM, 18-135 STM and T4i from B&H with their permission for this review and returned it afterwards.

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Anonymous said...

You are comparing 5D with 1DSMKIII in the graphs from Slrgear (which is not fair, because resolution in Slrgear tests depends on the camera sensor pixels count). Also, the bookshell doesn't takes into account the slight field curvature of this lens (for not so close subjects, the edges of the 40mm are indeed sharper, specially compared to that of the 24-105). The 40mm is a great landscape lens for the perfectionist (while nearly no zoom is).

Unknown said...

Strange ,40mm is a very sharp lens and build quality is excellent What are you talking about???

ronmartblog.com said...

Hi George,

A lot of products come my way for review and this one just didn't impress me much.

Great photos can be made with any lens, so if it works for you then enjoy it and make great photos with it!