As a photographer I can always recommend Canon. This is a great product and it really has only few downfalls to it.1. AF is very slow, so busy scenes are not for this product2. With adapter to use normal EF-S lenses the AF slows down even further3. EF-M lens availability is very limited, which brings you back to the point 2 above.But you get bang for your buck if you can live with the above. Digic 5 processor, touchscreen and the great Canon quality if you shoot more portraits, night scenes and landscapes in general. If you have few canon ef-s lenses you like and need cheap but great EOS experience on the road while not wanting to carry e.g. heavier 6D, 5D bodies... then this is great way to go!

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.

Absolutely perfect adaptation of EF lenses to my M series cameras. Basically feels like native lens. I have also used a third-party adapter, which is fine, but the AF takes just a little longer. Seems to have to micro adjust, whereas Canon adapter is just instantaneous.

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)..

EOS-Rで使用。純正Canon以外含むEE レンズ３本とEF-Sレンズ７本、普通に使えました。EF-SレンズのクロップはCanon製は自動で、シグマのArt 30mm F1.4 DC HSM、シグマの17-50mm F2.8 EX DC OS HSMも自動、タムロンの16-300mm(B016E)とトキナーのAT-X 11-20mm F2.8 PRO DXは手動で設定が必要でした。EOS-Rは80Dからの買い替えですが、どのレンズもAFの速さは変わりないです。正直なところダメ元で買いましたが手持ちレンズ全てが動作し、嬉しい誤算です。質感も約７千円の値段を考慮すれば十分です。KenkoのTELEPLUS HD C-AF 2X DGX との組み合わせはレンズによってエラーが出て作動しませんでした。使える場合でも流石にAFは遅くなります。

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 :)