Revision: 20130617_090100 | All Revisions
Instead of going with the established and highly acclaimed UltraSonic Motor (USM), Canon decided to use its new STM technology in this lens. The reason is because
Whereas the USM is a combination of mechnical and electrical mechanism, the STM is practically an electrical system. With USM, the manual focus ring is always mechanically engaged to the focus mechanism. That means you and manually adjust focus after AF is achieved without changing the mode switch.
On the other hand, with STM, you are either in AF or MF mode. Rotating the focus ring in AF mode does absolutely northing. Switching to MF mode does not engage any mechanical connection between the focus ring and the focusing motor. In MF mode, the focus ring controls the motor "by-wire", similar to the concept of "drive-by-wire" in modern cars. This means when you rotate the focus ring, the camera computer senses your adjustment, then adjusts the focus motor to match. But even with this mechnical disconnect, manual focus feels precise and responsive.
The STM is almost as quiet and fast as USM, but not quite. You can hear motor noise similar to the old Canon DC motor, but much quieter Almost to the noise level of USM. Out if the box, the 40mm pancake lens makes a really high pitch whinning noise. But this noise disappeared after a few days of use.
When I first read the Canon ES-52 lens hood model number on the Canon 40mm lens box, I thought it shared the lens hood from the Canon EF 50mm f/1.8 II lens. Both lenses have 52mm filter thread and uses a screw on lens hood. But when I took my Canon EF 50mm f/1.8 lens out, I found that the Canon 50mm lens actually uses the Canon ES-62 lens hood. But I decided to try this lens hood on the Canon 40mm lens anyway.
The Canon ES-62 lens hood has an adapter that screws onto the front of the Canon 40mm lens. After screwing the adapter onto the lens, the lens hood can be clipped onto the adapter.
The Canon ES-62 is rather huge compared to the Canon 40mm pancake lens. It doubles the size of the Canon 40mm lens and more. But it provides a very secure feeling and seems to do a good job blocking flair. It doesn't cause any vignette either.
Therefore, the Canon ES-62 is well-suited for the Canon 40mm lens. If you feel the Canon ES-52 is too small for your liking, you can try the Canon ES-62 lens hood.