Why is the new �400mm DO II the telephoto lens for everyone else? �Well, when mated with an APS-C camera and a 2X extender (with which it works well), it has the serious reach of 1280mm. � It is the second cheapest of all the expensive telephotos lenses. �It is the lightest of all the telephoto lenses. �It is the smallest, and the easiest to handle of the telephoto lenses. �All of which means this lens is more likely to be attached to your camera as opposed to decorating the place where you store your unused equipment. �Now if you make a living with your camera you should get whatever it takes to get that money shot even if it is cumbersome, heavy and generally unpleasant to use. �Because, well, that’s why they call it work. �But if you are like the rest of us who just enjoy taking pictures and prefer to invest in equipment we will actually use. �And, you need, or just want, a telephoto, this lens deserves your serious �consideration.

Fits the lens perfectly and saves the paint job from all those little scrapes and scratches. I will continue to use this product.

I bought this for wildlife photography including birds. I have only been out a handful of times but I am pleased with the performance and happy with my choice. I had considered the 500 mm and 600 mm but both the cost and weight were a deterrent. This with the 2x tele extender gives me 800 mm at f/8 and I am able to hand hold it. Looking forward to using this more in the future

I own the 400 f/4 DO II and the superlative 500 f/4 L IS II, both purchased from B&H. I just returned (Feb.,2015) from a two week birding trip along the Louisiana and Texas gulf coast. My preference was to have the 7DII paired with the 400 f/4 DO II and the 5DIII paired with the 500 f/4 II. I successfuly used a 1.4 and a 2.0 Extender III with both setups. The 400 DO II acquires focus as well as the 500 II. Both are very quick. The build quality of the 400 DO lens is on a par with my 500 II. I have thousands of images to compare and I can say with complete confidence and all honesty the 400 DO II image quality is equal to the 500 II. I can hear the naysayers now but folks I have nothing to gain by reporting my findings. Heck, I spent the extra money to have the 500 f/4 L IS II and no regrets. IMO Canon DO optics and coatings for the 400 DO II set a new standard in the super telephoto world for light weight with 'L' glass quality. The 7DII and 400 DO II with a 1.4 extender weigh in at about 7.13 lb. and 896mm of reach. There simply is not another kit available to match the image quality along with the portability and reach of this Canon combination. Don't hesitate to own this fine lens. Just an aside IMO the 7DII body is a must have for birding or sports.

I bought the lens 6 months ago, primarily for birds in flight photography. It does an outstanding job. I like the lens so much, that I am actually considering getting rid of my 600mm lens. The 400 DO II lens is very sharp, and works great with both teleconverters. Autofocus is a bit slower, but image quality is still impressive. The size & wt. of this lens makes it excellent for hiking, and luggage carry on challenges with the airlines is over!

I have owned this lens for over a year and have really enjoyed using it. The lens has produced outstanding results. I also owned the version I of this lens previously. The IS is much improved which makes hand holding more productive. The images produced are tack sharp including use of a 1.4x teleconverter. Image quality is stellar. I use the lens with a 7D mark II body. I have been pleased with the results for both perched birds and birds in flight. The version one is a fine lens but I’m glad I upgraded to the version two especially due to the IS performance.

i bought this lens for my wife because my 500 f4 was too heavy for her. Now I find myself borrowing it from her. This is light enough to walk around with and the images are amazing.

Had a chance to use this side-by-side with the 400 2.8 III, also an outstanding lens. For my use, there was no noticeable difference in sharpness. I don't think I'll miss the extra stop on the 2.8 but I really prefer the handling of the DO.
Paired with a 5D3, very fast focus. Very happy with this purchase

I am a huge fan of my Canon 600mm f/4. The sharpness of that lens continues to blow me away. I realized that over the past few years all my wildlife pictures were taken between 400-800mm. My next in line lens fixed tele-lens was an old 300mm Sigma f/2.8 without IS. I was looking for a lens that is easy to handheld and that performs reasonably well with my x1.4 and x2 latest generation extenders. I choose the Canon 400mm f/4 DO over the 200-400 (x1.4 internal extender) mostly because of weight and price. I choose it over the 100-400 f/4.5-5.6L mostly for better AF performance. I literally just received my 400mm DO and I spent a few hours today testing it along some Southern Californian beaches. I used it handheld with IS set in position 3 and with my 3rd generation x1.4 tele. For more pictures I invite you to look at francois_visualarts on Instagram. I love this lens.

I recently switched systems from Nikon to Canon and a fellow photographer who shoots Canon has this lens and he recommended I consider it. I rented one to try for a couple of motorsports events I was shooting and it performed outstandingly on my 5D MK4 and especially on my 1Dx MKII. In my previous system I had a 400mm f2.8 and this lens on the Canon bodies and with there ISO performance, I do not even think about it being an f4. The image quality with this piece of glass is phenomenal and pairing it with the 1.4 extender renders no loss of sharpness or image quality. The size and weight on this lens is another plus and it weighs at least half of what my old systems 400mm did. It's a bit smaller than the 300mm f2.8 and I can hand hold this all day and not feel any fatigue at all. If your looking for a 400mm consider this one. Rent one or borrow one and try it. You will be pleasantly surprised. The price point on this lens for what I get is a great deal and value as well. Love it and the images it produces.