My wife uses it on her EOS R6 and really likes it. She shoots mostly birds, but really, anything that catches her eye. It will focus really close, for a tele, so it makes it versatile enough for her to use as a walkaround lens. I've used it on my EOS R5 and it holds up to my scrutiny when peeping. Not sure if this will help, but I've thrown in a few images. All have been edited in Canons free Digital Photo Professional 4 (DPP 4) then cropped.
Almost all of my lenses are Canon L series but I went a different direction when I decided to pick up something lightweight and versatile for hiking when I don't want to carry one or more of my Canon "great white" L series telephoto primes. I ordered a Sigma 150-600 "contemporary" to try to see if the tradeoff of quality (both image and build) vs weight and versatility was acceptable.
I was pleasantly surprised with the performance of the Sigma lens. It doesn't measure up to the quality of my Canon primes and it has a much narrower aperture than my 200, 300 and 400 primes but for the weight, cost, and versatility of a single lens for casual hiking I am very happy with it.
The first photo was taken with the Sigma 150-600 on a 1DX II body, the next two were with the Sigma on my 1DX III body, and for comparison the last photo was with Canon's excellent EF 800 f5.6 prime on my 1DX III. All of these were taken pretty casually while hand holding the combo and files sizes were reduced for the last three to fit forum posting requirements so better results are certainly possible.
You are asking about the Canon RF 100-400mm f/5.6-8 IS USM Lens? I always or most always advise folks buy Canon if they can. Only if there is good reason not to, go to the aftermarket. This zoom FL has been a curious case. Canon didn't and doesn't see fit to produce a lens in the very popular super zoom lens like the 150-600mm offerings by Sigma and Tamron. I probably see more of them more often than any other tele or super tele than all the others combined. One exception in the pro sports world where Canon teles dominate.
The Canon RF 100-400mm f/5.6-8 IS USM Lens is a very good lens at a very attractive price. This would make your choice, would 600mm vs 400mm be worth the extra money a 150-600mm super zoom cost? In my mind it is worth it. Bird photography needs all the native FL you can get as they say, you can never have too much FL.
Rodger asked me this question a little while ago. I recommended he try one. He bought the Sigma C version of the 150-600mm. He is very happy with it as you can see. He has a stable of very expensive Canon L super teles. He is also very talented and dedicated to photography (that helps 😊). However, if I were buying today I would have bought the Tamron version. The Tamron SP 150-600mm f/5-6.3 Di VC USD G2. It has a slight edge over the Sigma C model. The Tammy is weather sealed. The Siggy is not. The Tamron G2 is also a tad bit better IQ wise. These will cost you more than the Canon RF 100-400mm f/5.6-8 IS USM Lens so you need to decide if they are worth it.
I can say this with some authority as I have owned or used every model of these super teles from the very beginning. Me personally I sold off all of them and kept the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens. My overriding reasons were far better weather sealing and built to professional standards as these are my greatest concerns in any lens. The negatives are very heavy and more expensive lens. However, as my retirement status has changed most all my photography requirements, I would opt for the Tamron SP 150-600mm f/5-6.3 Di VC USD G2 in a heartbeat!
It's a beautiful lens.
BTW, while on the subject, these are good candidates to buy on the used market. You can sometimes find mint copies for a very reasonable price. Folks get excited to get a super tele and some quickly find they are not a pick it up and shoot type lens. They take a certain amount of learning to get photos like Rodger has shown above. With that thought if you are not willing to commit to that, you may want to reconsider buying a super tele.
A couple nice accessories to go along with a super tele is a Black Rapid shoulder strap and a monopod. As to the used market, I would rate your choices the Tamron G2 first, the Siggy C next, and lastly the first Tamron non G2 models. Sigma also made a 150-500mm which can be found really inexpensive but QC on them is problematic. Try before you buy!
To the OP - I have neither the R7 or the Sigma 150-600, but I have a friend who has both. He cannot test the combination till later this month when his lens adapter arrives.
Do a YouTube and internet search on that combination. There are numerous reports of problems as well as statement that Sigma says lens is not compatible with AI Servo and eye tracking on the R7 (which would seem to be a primary use case for bird photography).
"The first photo was taken with the Sigma 150-600 on a 1DX II body, the next two were with the Sigma on my 1DX III body, and for comparison the last photo was with Canon's excellent EF 800 f5.6 prime on my 1DX III. All of these were taken pretty casually while hand holding the combo and files sizes were reduced for the last three to fit forum posting requirements so better results are certainly possible."
Again very nice shots. Some of your photos are nothing short of amazing for sure. However it isn't a fair or a good example to compare lenses when the subject, distance, camera or conditions are not exactly the same. One would also expect a $10,000 lens vs a $1,000 to produce a higher IQ photo.
This is a 100% crop and a good example why you never have too much FL.
It was with the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens. It was hand held and I was a few years younger! A 100% crop is pretty extreme and will really show up any faults quickly. The bird is a Ring Billed Gull. They are gregarious birds and will readily come to a few piece of bread tossed out on the ground or in the water.
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