bobmcculloch Loc: NYC, NY

Based on my 17-70 Sigma on my 2 Xanons I'd watch for focusing problems in close up shots, sometimes the camera lens combo hunts non stop at close distances, may not be a factor in all lenses but if I could try before buying I would!

whitehall Loc: Canada

I own the Canon 100-400 IS ii and the Tamron 150-600 G2. for BIF I have them on a Canon 7D mkii. While, the Tamron is as sharp in good light as the Canon, the AF on the Canon is faster, and it is lighter, which facilitates hand held shooting. However, if I try to shoot say birds in a rookery, and a tripod is an option, I will use the Tamron for the extra reach. Neither the 1.4 iii or the 2x converter give me any joy on a zoom lens.

brooklyn-camera I Loc: Brooklyn, NY

I shoot sports and the Canon 100-400 does a wonderful job. Fast and right on target, guess it depends on what you plan to shoot. I shoot 7DMKII and 6DMKII.

DebAnn Loc: Toronto

I have both Canon and Sigma lenses. They both perform very well.

wdross Loc: Castle Rock, Colorado

See if Image Resource has any data to compare.

Architect1776 Loc: In my mind

Quality there is NO comparison at all.
Canon is sharper across the full width of the image, especially as you go out from the center.
The Canon focuses closer than any lens regardless of make at 400mm and you feel like you have a macro lens by comparison.
Quality of build is the best in class as well, Read Lens Rentals tear down of this lens and you will be amazed at the level of quality compared to all others.
The only thing where the Canon does not beat others is in price, but the factors above explain the difference. But you pay for what you get.
Finally, the Sigma and Tamron G2 lenses are incredible lenses in the class and if there is a budget limitation will provide stunning photos as well. They just come up short in some ways.
The biggest seller for me was the close focus, when walking in the woods I leave it on and can get small flowers and bugs without having switch lenses and that is a game changer.
Today all are very good so have fun choosing then learn your lens and get some great shots regardless of choice.

DennisC. Loc: Antelope, CA

The Sigma 100-400 is part of the Sigma Contemporary line of lenses, it is a budget friendly lens that can produce good images with proper technique. The Sigma Art and Sport line are more expensive and ment to compete with the best that Canon, Nikon, Sony and Fuji have to offer at a slightly lower price.

jeep_daddy Loc: Prescott AZ

This is a partial image from a previous post from someone with a 150-600 Sigma. They are complaining about sharpness at 600mm. You can see why.

If you think this image is sharp enough for you at 600mm, then buy a Sigma. Otherwise you might want to consider the Canon 100-400mm lens. They are tack sharp at 400mm

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But, if you want a tack sharp image like this, buy a 100-400 Canon lens

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cjc2 Loc: Hellertown PA

I too am a Nikon user, but I can tell you Canon makes some damn fine lenses. I am also a BIG fan of any/all Sigma ART lenses ( I own the 24-105, 35/1.4, 50/1.4 and 135/1.8). Generally speaking, OEM lenses are a bit better, but not always, and it does depend upon what you need/want, money and specific comparisons. For example, my Nikon 200-400/4 is nice, but my Nikon 400/2.8 FL is fantastic. Neither are cheap! Best of luck.

ggab Loc: ?

The bottom line:
If you can afford the Canon L glass, get it.
If you can't, get Sigma or Tamron.

It's as easy as that.

rjandreoff Loc: Hawaii

I posted on this topic earlier this year. So....re-post.

Dustin Abbott's youtube piece offers a very valuable assessment on this very topic. After reviewing it, a friend of mine and I went into the field to test it for ourselves. He currently owns the Canon 100-400 L II, paid about $1800 for it, and loves it. After using it for a fews hours (mounted on Canon D5 MIII), it was clear to me that is a terrific lens! 9.9 on a scale of 10. I shoot Nikon (so do not have that choice) and decided to purchase the Sigma lens for B&H (Nikon version) with the dock, B&W filter, 4 year extended warranty, and cleaning kit for $670 plus change. At the end of the field test, we both concluded the Sigma results were quite close to the Canon it terms of overall performance. IQ was almost identical in nearly everything did. But the AF came up short on the Sigma. More than I liked. But then again the Canon's was utterly amazing. Never missed. Sigma's build quality is not what one would call "PRO" like the Canon. But that also lends it to being extremely light and manageable for field use. The Sigma did surprisingly well in close ups, better than specs would indicate. Bokeh was very pleasing. I have read/heard about quite a bit of Chromatic aberration, but we saw little evidence of anything excessive. Easily corrected in post. The Sigma is a REAL value. AND mine worked great right out of the box on D800e and D4 bodies. No dock adjustment needed. I am keeping the lens and using it a lot.

ggab Loc: ?

Did your friend that shoots Canon Sell his 100-400 and buy a Sigma?
BTW, my Sigma shooting with a 7DII, 5DIV and 6DII needed micro focus adjustment on all bodies.
I tested my Canon lens and came up with 0 adjustment needed on all bodies.
I use Reikan FoCalPro for micro adjustment.

amfoto1 Loc: San Jose, Calif. USA

Canon EF 100-400mm f/4.5-5.6 IS USM II versus Sigma 100-400mm f/5-6.3 DG OS HSM "C"...

The Canon lens is a lot more expensive, is better built and sealed for weather/dust resistance and about 1 lb. heavier, is at least 1/3 stop and up to 2/3 stop faster than the Sigma at many focal lengths, comes with a tripod mounting ring which isn't even an option with the Sigma... and the Canon uses fluorite in its optical formula, part of the reason it has better image quality. Fluorite is particularly helpful reducing chromatic aberration that can occur with telephotos... especially complex telephoto zooms.

Canon was on sale recently, but no longer is.... it's now $2199. The Sigma is on sale for $609 (reg. $799)

....versus Tamron SP 100-400mm f/4.5-6.3 Di VC USD.

You might want to consider the Tamron SP 100-400mm too. It's in between the Canon and Sigma in size and weight. It is closer to the Canon lens in speed... 1/3 stop slower at some focal lengths. Doesn't come with a tripod ring, but an optional one is available (sold separately for $129, but has built in Arca-Swiss dovetail, so no quick release lens plate needed if you are using the A-S system). The Tamron 100-400mm is selling right now for $799 (lens alone, tripod ring sold separately).

All three lenses have image stabilization and all three use their manufacturer's form of ultrasonic focus drive, which is fast and accurate. The differences in max apertures probably will effect AF performance in some situations.

This review of the Tamron lens (which was the last of the three to be introduced), shows a comparison of the focal lengths and max apertures of the three lenses: https://www.the-digital-picture.com/Reviews/Tamron-100-400mm-f-4.5-6.3-Di-VC-USD-Lens.aspx

Notice how the Sigma starts out at f/5 at 100mm, while the other two lenses start 1/3 stop faster at f/4.5. Further, the Sigma drops to f/5.6 at a mere 111mm.... while the Tamron doesn't do so until 181mm and the Canon lens at 312mm! 1/3 to 2/3 stop doesn't seem like a lot, but might be the difference between getting the shot or not in a sports or wildlife shoot.

The Canon 100-400mm II has a permanently installed tripod ring with a removable "foot". The shape and design of that foot might be "sexy", but it doesn't work well with lens plates if planning to fit one for a quick release system. I replaced the foot of mine with one from Hejnar Photo, which added $75 to the cost of the lens (but since the Hejnar foot has built in Arca-Swiss dovetail, there's no need for a separate lens plate, and some savings that offset the cost of the foot a little). Kirk Photo, Really Right Stuff and some others also make replacements for the Canon tripod ring foot.

The-Digital-Picture web site has in depth reviews of all three lenses. I linked to the Tamron lens review above. Here are links to the Canon and Sigma lens reviews:
https://www.the-digital-picture.com/Reviews/Canon-EF-100-400mm-f-4.5-5.6-L-IS-II-USM-Lens.aspx
https://www.the-digital-picture.com/Reviews/Tamron-100-400mm-f-4.5-6.3-Di-VC-USD-Lens.aspx

That web site's reviews include an Image Quality tool where you can make side-by-side comparisons of magnified test shots done with each of them, to see for yourself. There are also other tools to compare vignetting, flare resistance and distortion. Here's an Image Quality comparison example for the Tamron 100-400 vs Canon 100-400:
https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1178&Camera=979&Sample=0&FLI=0&API=0&LensComp=972&CameraComp=0&FLIComp=0&APIComp=0

You can change the lens selection, change a zoom's focal length, and change the lens aperture to see how different combos perform and compare. You also can change the camera the lens is tested upon... I left it set to the 5DS-R, which with 50MP is extremely "demanding and critical" of lenses!

Finally, the guys at Lensrentals.com see an awful lot of lenses and how they hold up over time. They also love to take things apart, just to see what's inside. When they did that with the Canon 100-400mm II, they called it "over-engineered" and something like "the best built zoom they'd ever seen". Here are links to their teardown blog post, as well as a followup about image quality (they test every lens when it's returned from rental)...
https://www.lensrentals.com/blog/2015/02/canon-100-400-is-l-mk-ii-teardown-best-built-lens-ever/
https://www.lensrentals.com/blog/2015/08/canon-100-400-is-ii-mtf-and-variation-tests/

Someone in Germany was 3D printing a tripod ring for the Sigma lens, but it wasn't able to rotate due to the way it fits around the buttons and switches on that lens. That sort of defeats one of the main purposes of a tripod ring on a telephoto... ability to rotate the lens to portrait orientation while keeping it balanced and centered over the tripod head. This is possible with the Canon lens, as provided... or with the Tamron after the optional ring is fitted to it. I'm not sure if the 3D printed ring for the Sigma is metal or plastic, either. If it's plastic, I wouldn't have a lot of confidence in it.

All three lenses come with lens hoods. The Canon's is nice and deep. The other two lenses' hoods are a little more compact, but those lenses have smaller diameter barrels, too. The Canon uses 77mm filters, while the other two use 67mm.

https://www.bhphotovideo.com/c/compare/Canon_EF_100-400mm_f_4.5-5.6L_IS_II_USM_Lens_vs_Tamron_100-400mm_f_4.5-6.3_Di_VC_USD_Lens_for_Canon_EF_vs_Sigma_100-400mm_f_5-6.3_DG_OS_HSM_Contemporary_Lens_for_Canon_EF/BHitems/1092632-REG_1362804-REG_1321312-REG

I don't have the Tamron or Sigma to compare myself, but the Canon lens works surprisingly well with a 1.4X teleconverter. (I used the 1.4X II, but understand the 1.4X III gives similar results.)

1st image below was shot with the Canon 100-400mm II + Canon 1.4X II teleconverter combo... 2nd image was shot with the lens alone, no teleconverter. These aren't my greatest shots, but both are sized to make 8x10 prints at 300 ppi, which makes them quite enlargeable online for image quality comparison:

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rjandreoff Loc: Hawaii

Hi. Sorry for any confusion. NO, he did not. He will never sell that lens. And he should not. Amazing piece of glass. BUT it is $2k (new) on a good day. I shoot NIKON, he shoots Canon. He and I are both "semi" pros which means we don't make a living with photography but we do get paid. Local sporting events, weddings, global travel (me), and wildlife. I needed a "walk around" field lens for travel and wildlife BUT hated the IBM's 80-400. It's $2k price tag plus only OK performance did not do it for me. Canon is the standard in this class. Research led me to Sigmats version of that lens. I decided to give it a go. I bought it from B&H with the thought that if it did not prove itself, it was going back. The proof was our ALL day field outing in the Hakalau Forest Reserve on the big island of Hawaii. Ultra demanding shooting conditions. Rain, wild, heat, altitude, rough terrain, plus a tiny population of native birds that do not show themselves easily. Results are on my Website if you wish to take a look. We were both amazed. Bokeh, IQ, color rendition, AF speed/quietness were all pretty damn close. Canon's AF precision was scary good! 100%. This was a Sigma weak point. Canon's build (like a tank) and to some degree weather proofing was better. He and I both prefer OEM glass when we can get it. BUT, if he was buying today, REALLY it would be a tough choice. His words. Nearly $1400 difference. And the Sigma is very good! I am very please.