The product works good with my Canon mirrorless camera with Sigma Ef 18-250mm lens with all functions. But the cost of the product is only Rs.7500 in canon showroom. This product is in great demand and not in stock so they are selling at an extreme price. If you can wait just place an order with canon and get it at a lower price

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.

The EF 17-40 will not give you f/2.8, and at f/4 it is not the sharpest. Even so, with a tripod at f/5.6 to f/8 and beyond it is a match for the EF 16-35. Therefore, although as a walk-around lens it cannot compare to the more expensive lenses, if you want to do landscapes, it is by far the best buy in the wide angle L series of Canon--and it will not be bested by the EF 16-35 at the apertures where it is most likely to be used for landscape photography. Combined with its light weight, it is ideal for packing into the mountains or other back country.I would like to give it five stars, but its limitations at f/4 would make that less than honest.

Low light loss & distortion on my Sigma 17-50mm f2.8 zoom. It was worth not getting an "el cheapo" filter!

This adapter did the job! I can now use all my Canon, Tamron and Sigma lenses on my new Canon m50.

Works very well on my Sigma 17-50 lens. Thank you.

The walkaround lens. This very topic leads to a heated discussion among DSLR photographers.First, determine your budget, focal length, and aperture needs.If you frequently find yourself zooming out to get everything in a frame, you will want a wide angle lens such as this. If you frequently find yourself zooming in, this is not the lens for you. On a full frame body such as Canon EOS 5D, this lens becomes ULTRA wide angle. On an APS-C crop body such as Digital Rebel XTi (which I used for this review), it becomes MEDIUM wide angle. But thanks to 1.6x crop factor, this lens expands to more usable 35mm equivalent focal length of 27 to 64mm.Second, audition the lens if you can.By definition, a walkaround lens should be relatively portable. At 1.1 lbs., Canon's EF 17-40mm f/4L USM is neither super light nor neck breakingly heavy. In fact, it weighs almost the same as Digital Rebel XTi -- really nice balance. The lens feels very solid with supreme build quality that only L-series lenses offer. Although this lens is weather proof and therefore sealed against liquid and dust, I strongly recommend getting a 77mm filter to protect the front lens element. With it, this lens is made to last.In terms of looks and feel, it doesn't get much better. Its rubberized full-time inner focus manual ring USM focuses smoothly, quietly, and quickly. Since it's inner focus, the lens will not extend beyond its metal casing whether you zoom in or out. The focus window shows focusing distance from 0.28 meter (0.92 feet) to infinity. The focal length marker indicates 17, 20, 24, 28, 35, and 40mm. The lens exudes quality from tip to tip.You may tolerate heavier lens or may not mind lesser build quality of cheaper lenses. A walkaround lens will be used very often, so make sure you will be comfortable with it.This lens is famous for saturated color and deep contrast. Its images are simply stunning. At 17mm wide angle, barrel distortion is noticeable but relatively mild. From 24mm to 40mm, its images are distortion free and perfectly suited at capturing people.Vignetting (corner darkness) is minimal with mild chroma abberrations (color shadows). At f/4 aperture, details become noticeably softer toward the edges. The center region is very sharp and at f/5.6, edges remain fairy sharp. Thanks to 7 diaphragm blades, this lens can produce very nice bokeh at 40mm (blur effects).One of the most cited weaknesses is the f/4 aperture. In my experience, a bump in the ISO speed and steady hands are all you need to take well focused images indoor. On the other hand, if you are shooting with very little amount of light, you might wish for f/2.8 or image stabilizer. Although the difference between f/4 and f/2.8 is just 1 stop, my other lens, Canon EF 24-70mm f/2.8L USM (too heavy to be my walkaround lens) easily outperforms in such challenging situations. But by and large, I was not handicapped by the f/4 aperture.Some of the main competitions (sorted by price):- Sigma AF 17-70mm f/2.8-4.5 DC macro: Good zoom range with macro, and generally solid performance if you can get a good sample. It does suffer from a bit slow focus mechanism, soft corner, and chroma aberrations. Works only with EF-S mount.- Sigma 18-50mm f/2.8 EX DC: Very good value for f/2.8 aperture, but Tamron's 17-50mm is a bit better lens overall. Works only with EF-S mount.- Canon EF-S 17-85mm f/4-5.6 IS USM: This "traveler's lens" has a wider focal range than most wide angle lenses (widest among Canon) and is equipped with an image stabilizer. While it is a Jack of many trades, it is the master of none. Every lenses on this list will perform better at particular focal length. Then again, none of the lenses on this list has as wide focal range. It is famous for extreme barrel distortion at 17mm and chroma aberrations. Works only with EF-S mount.- Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF): This is the most direct competitor. It takes sharper images with faster aperture while costing less. Both the build and focus mechanism are significantly worse, but should be good enough for many. Works only with EF-S mount.- Canon EF-S 17-55mm f/2.8 IS USM: This is THE reference, if you can afford it. Its images have razor sharp details and great performance all around (minus vignetting, which is typical of EF-S lenses). The build quality is worse than L-series but still pretty good. Works only with EF-S mount. This is the best EF-S lens hands down.- Canon EF 16-35mm f/2.8L USM: One of the most expensive wide angle zoom lenses. It's larger and heavier, but has f/2.8 aperture.This is how Canon EF 17-40mm f/4 USM stacks up.Pros:- Among the very best build quality.- Excellent, buttery smooth, super fast front-focus system.- Top notch color and contrast. Very sharp center resolution.- Almost non-existent vignetting, generally low distortion, and well controlled chroma abberrations.- Ideal weight and size for walkaround purposeCons:- Edge softness at f/4 aperture.- Narrower focal length than most competing lenses.- Slower than some third party lenses.All in all, this is an excellent wide angle walkaround lens. It may not offer the most bang for the buck, but if you value full frame compatibility (EF lens mount) and excellent build quality, this is the default choice. This lens comes with a nice pouch and a lens hood. I find the hood to be somewhat ridiculously shaped and because the lens is resistant to flare, I do not use it often when shooting outdoor.

I debated for quite a while between this lens and the 17-55 f/2.8 EF-S IS. I'm still drooling over that lens, but what it came down to in the end was my plan to upgrade to the 5D when, and if the Mark II is released. Of course, the other lens that could have made the decision even more difficult is the 16-35 f/2.8L, but it was way out of my price range.I'm happy with my choice. The lens is well built and sharp. If I have any complaints it would be CA. This lens does tend to show a bit of color fringing, but nothing and extra five seconds in raw processing can't fix. So I guess that point is moot.Overall, this is a good lens. Well worth the money. Especially at this price.