Update 8-21-12: Scroll down for updated 40mm firmware
I have had in my hands the 40mm STM for a little over 12 hours so this is really going to be my initial thoughts.
I love how small it is, on the 5D Mark III it doesn’t stick out beyond the grip. On a Rebel it makes an already fairly portable body even more svelte. Build quality is solid
and it does offer full time manual – though the focus ring to grab is, not surprisingly, very slim. For the most part the focus ring rotates smoothly but you really won’t want to spend lots of time manually focusing with this lens. Auto focus is quick and very quiet. As far as I cant tell it isn’t much different from USM of other nicer quality lenses. Minimum focus distance is just under a foot with 0.18x magnification.
I will be helping out with a wedding later today and since I will be the second shooter I plan to use this. I think the question all non-T4i owners should be asking is “is there any reason I should buy this lens?” Initial quality comparisons against the 50 f/1.4 which costs almost double shows the at f/2.8 the 50 f/1.4 is a good bit sharper, at f/5.6 this difference is all but gone but the 50 has nicer contrast. Against the 35 f/2 the 40mm is the winner in focus speed, image quality and bokeh quality. The 35 is slow to focus and a bit noisy about it as well. Against the 50 f/1.8 the 40mm wins here as well though at only a $100 the 50 f/1.8 is an excellent buy if you are on a serious budget. But for many of you on crop sensors the 40mm is just a bit wider and nicer to work with, especially indoors. If you own or are purchasing a T4i I think this purchase is a no-brainer, it will give you a lens capable of silent and continuous AF while filming for only $200. The rest of you would probably be better saving a bit more for the 50 f/1.4 but there is no harm in having it as an option in your bag.
Update: I think I am going to keep this lens – it is just so tiny, so nice to have as an option when I want the full quality of my DSLR but without a big heavy lens. And I have been quite happy with the quality and the focus speed.
Note: The 40mm will work fine on all Canon cameras but it does not magically offer continuous auto focus, you must have the Canon T4i for it to do that.
Update #2: Review of the new 18-135 STM Lens
Update #3: The recent 5D Mark III firmware has a note that it includes support for the 40mm STM lens – this does NOT mean that it will now do continuous auto focus during filming with the 40mm, What it does do is allow full time manual focus, this is a focus by wire lens and when you rotate the focus ring it is sending a signal to the lens to change focus, you are not directly changing the focus. 5D Mark III firmware is available on Canon’s Website
Update #4: I have had this lens over a week now and used it at two weddings for detail shots and a few other odds and ends – I am very impressed with the quality and the focus speed – on par with other much more expensive lenses. This is really starting to look like a no-brainer purchase for anyone with a Canon DSLR. Let me make it even simpler. Do you own a Canon DSLR? Yes? Go buy this lens.
Update #5 – Firmware Version 1.2.0 for the 40mm f/2.8 STM Lens addresses the following phenomenon
1. If pressure is applied to the lens barrel while the lens is mounted to the camera (pressure can be applied even while attaching the lens cap or while carrying the camera with the lens attached in a bag), the autofocusing function of the lens may stop working.
A Canon EOS 1D X, 5D III (at v1.1.3 or later) or a Rebel T4i/650D is needed to install the upgrade. Alternatively, the lens can be sent to Canon Service to have the firmware upgrade installed.
Buy the 40mm f/2.8 STM Canon 40mm EF f/2.8 STM Lens (In Stock now)
Buy the 50mm f/1.8 Canon EF 50mm f/1.8 II Camera Lens
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