I recently decided to make the switch from a Canon DSLR to a Canon R mirrorless. It was easy to learn since I'm already used to Canons. I bought the EF to RF adapter (with the adjustable ring) so I could use my DSLR lenses with it. My only complaint is that Canon should give you the adapter free (they used to!) when you buy the camera. So far, it's taking good photos, and I decided to buy the kit lens that goes with the camera, so I can use it for all-around use when I'm out and about. I have a very nice Sigma macro lens that I bought at the same time, which needs the EF to RF adapter, but it takes very nice macros on this camera. I'm glad I bought it.

I purchased this adapter along with the EOS M camera kit to use with my EF and EF-S lenses. After less than a week, I have been able to try out with the EF 50mm F1.4, EF 70-300mm L, EF-S 17-85mm, and EF-S 60mm lenses. The adapter fits perfectly. Same form and fit as the Canon extenders I have. The EOS M is of course made very tiny with any large EF lens. It creates a sort of 'pocket Rebel'. Of course, once you mate with the larger lens, this is no longer going to fit in anything less than a massive coat pocket. The combination of camera, adapter, and lens seems comfortable after brief handling. The EF 50mm was a very comfortable combination, the adapter does not add a very large amount to the overall combination. The upside to this adapter is if you already have a variety of EF and/or EF-S lenses. The image quality of the JPEGs, right out of the camera ranged from expected to stunning (the latter results obtainable with off camera studio flash strobe and soft box). The adapter was immediately a huge part of the EOS M camera purchase. I highly recommend it if you have other lenses. Again, the results I got with the EF-S 60mm macro (and studio lighting) were stunning. It transformed the camera from curiosity to studio prime. No problem using manual mode and Pocket Wizard. Include this adapter in your purchase and you won't be looking back.

The wide zoom--16-35, 17-35, 17-40, 20-35, et al.--has been a mainstay of pros, especially photo journalists, since the early 1990s. These focal lengths are ideal for sweeping views and shooting in tight quarters, and are easily hand holdable. The 17-40L is my go-to wide zoom for landscape shooting on my 5D MKII and 6D. Important note: if you use a 1.6X cropped frame camera, e.g., Rebel, 60D, 70D, etc., this zoom will have the field of view of a normal zoom, i.e., 28-65mm equivalent.CONSTRUCTION: Canon's EF 17-40 4L USM brings together precision optical design, blazing AF, durable construction and silky smooth zooming. At $750, it's more affordable than the EF 16-35 2.8L USM II, but offers similar build and optical quality. The hybrid metal and polycarbonate construction and quality components make the EF 17-40 4L USM tough as nails, but a lightweight 475 g (16.8 oz). Plus, the moisture and dust seals, including a rubber O-ring on the lens mount, make it a great choice for jungle and beach shooters. Canon recommends use of a clear or UV filter to complete weather sealing (front element moves slightly when zooming).The EF 17-40 4L USM is a classic two-touch design: manual focus ring near the end of the barrel and zoom ring near the mount. Handling is nimble and decisive. Both zoom and focus mechanisms are internal so there is no nested barrels. Plus, internal mechanisms are less prone to sucking in dust than front extension designs. Unlike most AF lenses, the manual focus ring is large, ribbed, rubberized and nearly as smooth turning as the manual lenses of yesteryear. The satin black finish is elegant and the overall appearance similar to the EF 16-35 2.8 USM II and EF 24-105 4L IS USM.The filter size is 77 mm, making filters expensive. This size is common for L series optics, so you can share filters with the EF 70-200 2.8L IS USM and EF 24-105 4L IS USM. The clearance from the edge of the front element to the filter threads is huge and, subsequently, normal thickness filters such as a Hoya Super HMC UV do not vignette on full frame cameras like the 5D MKII or 6D.AUTO FOCUS: This lens sports a ring-type USM (Ultrasonic Motor) that drives an internal lens group and AF really rips. The front element does not rotate nor does the barrel expand or contract during focus and zoom operations. The motor of the EF 17-40 4L USM is silent during AF. It has Full Time Manual (FTM), allowing you to manually focus without switching out of AF mode. If you prefocus manually, the distance window in meters and feet is handy. AF worked flawlessly on my 5D MKII, 6D, 5D, A2, 3 and Elan 7E. That is, AF is fast, accurate and decisive.IMAGE QUALITY: The constant F4 aperture is a big plus for hand meter users and those that prefer manual or aperture priority exposure modes.I found EF 17-40 4L USM sharp and contrasty. There is slight improvement when stopped down to F5.6 or F8, but it is almost as good wide open. The contrast and snap of this lens is apparent even through the viewfinder. After all, there's exotic glass in there, e.g., 1 UD and 2 aspherical elements. The short end, like most wide zooms, shows some barrel distortion. The long end has a small amount of pincushion distortion. For most use, distortion isn't a problem save for architectural photography.Flare is well controlled for a zoom. However, some flare and ghosting may occur with bright sunsets. Use the included lens shade (EW-83E) to protect the lens and help keep flare in check. Incidentally, the included EW-83E is a weak design: too shallow and dish-like, yielding a minimal amount of protection. The EW-83H, a deeper and narrower hood intended for the EF 24-105 4L IS USM, gives better protection and does not vignette at any zoom setting on both full frame and cropped cameras.FINAL BLURB: I bought the 17-40 4L in 2003. Ten years of punishment at beaches, waterfalls, jungles and deserts and it's still going strong, having outlived at least a half dozen of my cameras! If you need the versatility of a wide zoom, this is among the best. The EF 17-40 4L USM has similar build and optical quality as the famous EF 16-35 2.8L USM II, but at nearly half the price, weight but shy a F-stop. For discriminating hikers, travelers, landscape shooters and serious amateurs this zoom deliverers quality without breaking their shoulder or bank and can take the knocks they dish out.

Good lightweight camera. Great value and with lens adapter I can use all my EF lenses.

The adapter is good, delivery was also very fast, i got it just in 1 day.. But if you really wanna use EF or EF-S lens in mirrorless cameras, you have to keep in mind that the sharpness will decrease by a little amount and you you have to focus the subject very correctly, otherwise the picture will become blurry(specially for the prime lens)..

So you finally decided on getting the EOS M (it's flaws considered). I assume you are a canon user, have a couple of good (canon EF/EF-S mount) lens lying around and would like to be able to use those on you EOS M. Just like me, you love your canon dslr but sometimes wish you can travel light but still be able to enjoy the canon ecosystem that you have grown to love. If you are what I assume you are, get this lens adapter.I took a gamble and bought a "like-new" used from a seller at Amazon and was very happy with a purchase. For anything more than $150 I probably would think twice. But I am not taking a start out because of the price. This adapter handles every canon mount lens I threw at it. The build quality is nice. The design (the way it attaches to the eos m; the included, detachable tripod mount) is well thought of... just perfect.

EF - Lens adapter perfect for wide angle and other type of lenses cheaper than the viltrox, and better to use since it is from Taiwan and made in japan i rather buy japanese and taiwanese products and support them since their quality is greater than Chinese, i support it since they actually are more detailed on the manufacturer and the way they actually do the diagrams and cuts are precise but i know the quality is even stronger and more durable than chinese cheap brands. Love japanese quality and brands.

It's an adapter - it allows me to put my EF glass on my EOS-M and they are fully functional when mounted. AF, Metering, aperture control - all good. Made of metal and I appreciate the tripod mount on it - handles my 70-200 f2.8 IS II without a problem although it looks pretty much like a rear lens cap when setup that way :)