Canon EOS mag

Technique EF 40mm f2.8 STM lens

The EF 40mm f2.8 STM is the first Canon prime lens with stepper motor focusing technology. It is known as a ‘pancake’ lens, because of the short lens barrel. And it is more ‘standard’ than a 50mm lens. Andrew Gibson is impressed. Standard lens

A pancake lens is a bewitching object. Small, light and unobtrusive, it fits snugly in the palm of your hand or slips easily into your camera bag. What’s not to love? I’ve been keeping a covetous eye on the pancake lenses made for mirrorless cameras for a while, so when Canon announced their EF 40mm f2.8 STM lens, I bought it. I wasn’t the only purchaser – the shop assistant said six of the new lenses had been received from Canon and they had sold fast – mine was the last remaining. Why is this lens so popular? It’s partly the price – the retail price is under £230. The build quality is excellent, better than that of Canon’s least expensive lens, the EF 50mm f1.8 II (£129.99 RRP). The optical quality is superb. But the appeal of this lens reaches beyond all those things. It’s beautiful, simple and functional. Apple has been incorporating these aspects into its designs for years. Now Canon has done the same with the EF 40mm f2.8 STM pancake lens. Stepper motor technology Stepper motors date back to the 19th century. The technology has come a long way since then – making the motors smaller, quieter and faster. Your flatbed scanner or inkjet printer probably use stepper motors. Canon is not the first manufacturer to bring the benefits of stepper motors to lens focusing, but it is the first to bring the technology to DSLR lenses. A stepper motor converts digital pulses into mechanical rotation. One complete rotation of the shaft is divided into a large number of small steps. Each pulse rotates the shaft by one step and the position of the motor shaft can be controlled without any feedback mechanism. A large number of digital pulses give a very smooth rotation of the shaft. All this contributes to fast and accurate autofocusing. There are no contact brushes in the motor, giving the device a long life. The motor is reliable, rugged and relatively inexpensive (though not the cheapest option for lens focusing). It is also very quiet, making it ideal when the lens is used on an EOS camera shooting movies as the built-in microphone is less likely to pick up noise.

ALL PHOTOS ANDREW GIBSON

Above The EF 40mm lens looks tiny on an EOS 5D Mark II, but provides an impressive performance. The EF 50mm lens is often called the ‘nifty fifty’. One internet user has dubbed this new lens the ‘shorty forty’. Right The EF 40mm lens is perfect for portraits (see page 15). The lens lets you get close enough to fill the frame, but without introducing perspective distortion. The f2.8 maximum aperture makes it easier to shoot indoors without flash and helps to throw distracting backgrounds out-of-focus. EOS 5D Mark II, 1/125 second at f2.8, ISO 200.

The ideal walk-around lens 40mm is an interesting focal length. On the full-frame EOS 5D Mark II it is a moderate wide- angle lens – and barely that, considering a true ‘standard’ lens would have a focal length of just over 43mm (based on the diagonal of the image format). It feels very natural and is ideal as a walk-around lens – wide enough to provide an interesting perspective, yet not so wide that exaggerated perspective is a problem. A couple of factors piqued my curiosity. 1 On an APS-C camera a 40mm lens becomes a short telephoto (the equivalent of a 64mm lens on a 35mm camera) – ideal for portraits. 2 The minimum focusing distance is only 30cm. That’s close, especially when used with an APS-C camera, and I wanted to see how the lens performed with a close-up filter or extension tubes.

Actual size

Actual size

18 Reproduced from EOS magazine October-December 2012

Reproduced from EOS magazine October-December 2012 19