Tell me - when I wind nd on this lens - the filter is k & f nd8-nd2000 - the sharpness disappears completely, the video is like soap - what to do in this case, I need to darken it very much
@@cameralabs the fact of the matter is that the focus is manual. I tried the same k&f nd8-nd2000 ND filter on an rf 24-105 stm lens - everything is fine there. And on this lens with an ND filter, sharpness drops very much. I do not know what to do. I need to shoot the welding process from afar, but close-up so that the spatter from welding does not fall on the camera and lens
@@100amper hmmm, that is odd if it works ok on the 24-105. You could try and match the apertures on both lenses to see if that's the issue. So if you were at f8 on the 100-400, try the 24-105 at 105 f8 and see if it's similar or not.
I super applaud you for doing real life tests with the camera tilted. This is precisely how you judge a lens. Not charts. Lenses behave differently at infinity focus. You’re literally the only one that does this. I’ve been wanting to do similar reviews on RU-vid (I have had this and other ideas long ago) that will really show lens performance.
Thanks, I agree. Charts can be useful, but only for showing how well a lens will perform from, say, 1-2m away which may not be representative of how you'll actually use it. But people do it because it's easy, repeatable and comparable. Outdoor comparisons are hard with variable conditions, but I think worth the effort. Wish more people appreciated this approach, as it feels my videos take more effort and get less views than many, so a lose-lose on YT.
I have this lens and so far i’ve been immensely happy with it. Compact size and lightweight it’s a no brainer really for the hobbyist. I’ve got some really lovely shots during my nature retreat, including low light ISO cranked up to 11
Another comprehensive and excellent review Gordon. This performance is showing once again that Canon is improving non L lens quality to very high levels and this lens is going to be a big seller for those not wanting to splash the cash on the professional lens equivalent. The improvement in ISO performance coupled with the fantastic lens stabilisation of the latest R cameras has really given a great platform for these non L lenses which enables photographers to still enjoy some cropping of their images . Another cup of coffee ☕️ coming your way mate.
Great review as always Gordon! Just got this lens for my EOS R and for the money, absolutely loving it. It's replaced my EF 70-300 IS USM II + Adapter and is significantly lighter. The darker aperture isn't anywhere near as much of a problem as I would have assumed, with focus locking in all the way into evening hours. For anyone looking to take the same upgrade path, the hood of the 70-300 IS USM II is the same hood canon recommends for this 100-400, and the filter thread is also the same size.
@@cameralabs It definitely does! Only thing I notice with wildlife photography is the subject separation isn't as big due to aperture, but overall sharpness is absolutely better if pixel peeping. The extra 100mm is definitely nice to have though, for a hobbyist like myself that beats out most other negatives.
I actually have the same exact lens you do the 70-300mm is usm ii and was debating about getting this rf 100-400mm but been reluctant on doing so because of the weaker aperture. is the image quality and sharpness better on the rf 100-400 or the ef 70-300?
@Aquagene @Gordon Laing I actually have the same exact lens you do the 70-300mm is usm ii and was debating about getting this rf 100-400mm but been reluctant on doing so because of the weaker aperture. is the image quality and sharpness better on the rf 100-400 or the ef 70-300?
@@RandomGuy-qn2fr I didn't directly compare the quality, but anecdotally, they had a similar style looking through my various sample images. Lacking a bit of bite and contrast, but otherwise well corrected.
I recently got the Canon R6 and the Sigma 150 - 600 mm. I took this combo out and did some bird and bird in flight photography and was very pleased with it. Since then I just got the RF 100 - 400 mm and have only had a chance to use it for stationary bird pics but am very impressed with it. It is very light and so easy to carry. When using the Sigma after 3 hours my arm was getting sore, but I could carry this lens around all day without a problem. Also, I used the crop mode with the 100 - 400 mm to get more reach and it performed very well. I am very pleased and impressed with the sharpness and picture quality of the 100 -400 mm. I haven’t taken it out for bird in flight pics yet but hope to do so this week. Also, the macro capability of this lens is nice to have. For the price I think it is a good deal and lens to have in my camera bag.
@@Dewabarasunderan I think each lens serves its’ own purpose. The 100-400 is much easier and more comfortable to tote around and I think the auto-focus is a little better when used on the Canon R6 than the Sigma. The Sigma 150-600 has more weight and you feel it after a while. The image quality is very good. I went on a photography photo shoot at an indoor rain forest pyramid and brought the 100-400 and the 150-600. I found in lower light / indoor settings the 100-400 didn’t perform as well as the 150-600. I began shooting with the 100-400 but had to change to the 150-600. So, your question doesn’t have an easy answer. If you will be shooting outside and mainly with good light, the 100-400 might be a good option. If you need or want a little more reach and better low light capability the 150-600 is probably better.
@greadore how would you compare a cropped 100-400mm image with a more closely zoomed photo from the Sigma? Are they comparable quality? I'm planning on buying the r6ii, which isn't over performing in terms of megapixels, so one thing I'm concerned with is how cropped zoom photos will look, especially since I am coming from using a 70-300mm on an aps-c sensor (450mm FF equivalent) which I also regularly crop into.
Thanks so much for letting us download sample images. I sold both the Canon EF 100-400 L ii and the RF 100-500 lenses and moved over to OM for my long lens. I didn't like the way the extender restricted the lens on the RF model and the f/7.1 at the long end. I love the OM 150-500, but it is a beast to carry and hold. This one has me temped back again for a walkabout lighter lens for those days when you're not specifically going to photograph anything, but you might see something, or maybe a family holiday.
Great review Gordon! I just got this lens a few days ago and I’m really happy with the IQ and AF, it actually made me wish Canon used this Nano USM motor in their RF 35mm and 85mm lenses!
This lens paired with the R6 and either the 600 or 800 F11 lenses would be a decent wildlife kit without spending a lot of money. Sure it’s still expensive but compared to an R5 and 100-500 and 600 F4 it’s a bargain.
That kit (R6, 100-400, 800) is exactly what I’ve recently got, plus the 1.4 extender. Working well so far. Another thing to say about the 100-400 is how smooth it feels, really nice to use, feels like a premium product.
No, especially the 16 mm is clearly FF. It makes no sense on APS-C where the kit zoom would be as wide and almost as fast. Remember Sigma has 16 mm f/1.4 for EOS M. This replaces the EF-S 55-250 mm and the 16 mm replaces 10-18 mm for those who move from Rebels.
Another brilliantly comprehensive review, Gordon. I’m thoroughly impressed with this lens, and use it almost every time I go out to shoot landscapes. I have no regrets selling my EF 100-400. 👍🇦🇺🦘
@@cameralabs I had the MKII - purchased new last year. I loved that lens, but it made my bag too heavy, so I often left it in the car. Now, I have the RF version with me all the time, and for landscapes, I see almost no difference in image quality. And since I’m not Thomas Heaton, I don’t shoot in the rain, so the weather sealing isn’t an issue. It’s perfect for my needs. 😄
This to me feels like what the 55-250mm lenses are to crop bodies. An inexpensive but also effective lens for people that otherwise would have to pony up far more than they are willing/able, go to a third party that might have worse performance overall, or settle for something with less overall reach like a 70-300mm. Canon just seems to nail it when it comes to affordable lenses, and the new level of engineering for mirrorless seems to give them better options. Got to say I find it interesting they went with NanoUSM instead of straight STM, making it a far better lens for action thanks to speedy focus. They probably could have shaved the price to under 500 USD with STM, but glad they didn't. This is a real winner for Canon. I wouldn't even hesitate to suggest it to people in the RF system that really can't afford the more expensive models. I would most certainly not send anyone to the Tamron or Sigma 100-400mm that would cost more and have to be adapted, not even if it were a little cheaper than this lens, as the AF seems to be faster and likely better overall. Anothing thing I think that makes it interesting is the price pretty well puts third party lens makers in a place where they will not likely be able to compete. Tamron and Sigma's 100-400mm lenses frequently are around 800 USD. Granted that's the EF model, but even so, I don't know that they could make a lens that is cheap enough and still good enough to compete with this one, that is if they ever get around to making RF lenses LOL. I already tell people to not bother with the 70-300mm lenses they make, as the EF IS II model is so good for it's price that they just aren't cheaper by enough to put up with the inconsistent AF performance. I only ever recommend their 100-400mm lenses due to how expensive the EF L model is, or how much larger the 150-600mm lenses are. I really can't see them bothering at this point, since this will likely only get better in price as time goes on. They'd need to nail the IQ I think to be considered a better option, and the price would have to be right in line with it.
I watched this excellent review, then bought the RF100-400 lens. LOVE IT. Then yesterday I got the RF1.4x and it works fine. Given the fine low light performance of the R6, I often use auto ISO with very little noise.
Super interesting review. I'm currently using MFT to keep weight and size down, but this lens is lighter than even the Panasonic 100-400. Granted 2/3 stops slower, but with a four times larger sensor you'll still end up with shallower DOF and better noise performance. And if Canon decide to make a crop camera with RF mount and the 32MP sensor then we'll still end up slightly ahead in DOF and noise performance - and (slightly) higher pixel density than a 20MP MFT sensor. How Olympus/Panasonic decided to not make something like this or the Canon 600/800mm F11 must be one of the great mysteries.
I do think you should compare it to the panasonic 50-200 f2.8-4. Same equivalent aperture, but the pansonic is weather sealed and have better build quality and weight and cost more :)
I would be cool if Olympus or Panasonic made a 200-500mm f5.6 lens for MFT. I think the Nikon 200-500mm f5.6 is one of the best value for money wildlife lenses even now.
Thank you for this review of the budget 100-400mm RF lens. I own a Canon R100. I don't have any RF lenses to mount to my R100. I use a mount adapter to pair my EF glass to my R100. I am considering my first RF lens for my R100. This video gives me the knowledge to make an educated purchase of the 100-400mm RF lens to pair with my R100.
My guess is that this lens is mostly meant as a full-frame "equivalent" to how the 70-300 would appear for APS-C users. Even though it is a dimmer lens, the bokeh at f8 for full frame would roughly be equivalent to f6.3 (or 7.1?) on APS-C (not sure how to calculate this more precisely). That said, I do feel Canon is pushing too hard for smaller aperture lenses just because the AF and high ISO performance is meant to offset that. EDIT: Using a depth of field calculator, f8 is roughly equal to how f5 would appear on an APS-C (in terms of depth of field, not the amount of light hitting the sensor). On the other hand if the f8 was used on a crop body it would be f12.8!
I've this and it's a great all rounder for hiking birding and macro by cupping on a raynox 250. Together with the RF16mm it's a lightweight hiking setup!
I prefer these "real life" lens tests to those which rely on charts. Charts tend to be useful only in distinguishing excellent lenses from the rest. Most of us can't afford or can't justify the expense of the very best lenses. If a budget lens of a focal length you desire produces good images in most scenarios, it is worth adding to your kit.
Quite interesting that sony and canon have chosen to go in the opposite end. Canon trying to be innovative in the large telephoto section to bring these lenses to the masses and sony is trying to take regular lenses and make them smaller. Wild life shooters will definitely appreciate Canon's effort. As a street photographer I appreciate Sony's effort. Just ordered 5mm f2.5 G. Great job Canon!
I'm fortunate to have gotten my hands on the outstanding RF 100-500 F/4.5-7.1L but otherwise, the 100-400 is a great lens, especially at the price. I can't wait to get the 16mm F/2.8 for vlogging. P.S. "Steven Seagull" 😂
Canon won’t release APS-C R cameras. They more likely will simulate APS-C with some very very dark zoom lenses. Smaller and APS-C equivalent of f4-5.6.
I just purchased this one as well as the RF 16 f2.8. both are great lenses with some degree of compromise. I have only shot jpegs with both only because of the lack of profiles available, which will change shortly I presume. The RF 100-400 is great mostly. The AF is deadly accurate and I can't see any reason to complain other than it being dark. The IS is better than my 70-300 L lens. I've shot the moon handheld at 1/25 second at 400mm with no noticable movement. That is where the lens shines. Great review as always, even if I bought the lens first! Thanks!
I have the RF 100 to 400mm. I understand recommending using it in brightly lit situations or going for a larger faster lens, but the much heavier and way more expensive rf100-500mm is 7.1 at the long end. That's just one stop difference. You would have to go with a much more expensive prime lens to get f4 or even f5.6. I understand the difference in image quality you would expect from a $2,800 lens compared to this $650 lens but I believe it's the manufacturing quality and the cost not the aperture that is the biggest factor here. One stop of light really doesn't make much difference when you use denoise Ai and sharpen Ai and dxo pure Raw or other programs to clean up your images. It's just not a fact that the rf100-400mm is a dark lens and the rf100-500mm is a bright lens. I'm using faster than 1/1000 and often up around 1/4000 shooting birds and wildlife with auto ISO at 100-25600. Even on a bright sunny day I'll often have 3200 ISO because of my shutter speed at f8. I'm guessing the rf 100-500mm might give me 2500 ISO at those same settings. Definitely not worth four times the cost and carrying the extra weight all of the time for me. Working professionals or people with a much bigger budget would have a different situation but they won't be using the RF 100-500mm in low-light situations without ISO issues just like I'm having. Thanks for the detailed review and best of luck to you!
Amazing review dear Gordon, I was waiting for it to be honest, I'm considering this lens as I'm planning to travel on vacation soon, considering that I already have the EF100-400 and was trying to decide as it is really heavy. I will propably go for it.
Wow what an impressive review. I think you’ve convinced me to go pick one of these up tomorrow. Might see if I can trade in my old 80D body for it. Subscribed.
Excellent review in the field! I got the 100-400mm RF two weeks ago and I can attest to what's said here. The only, minor, complaint I have with my example is that the lock switch seems a bit fiddly and of lighter construction than on my RF 24-105 L f/4 lens with the lens snapping to unlocked operation after I tried to zoom without being aware the lock switch was on. I'll treat it with care from here-on and will try to avoid accidentally trying to zoom it while the lock switch is engaged. The difference in built quality between a L series zoom and non L zoom shows here. Then again, it's also not heavy like an L lens and considerably cheaper off-course ;-)
running two systems, I wonder about this in comparison with the MFT 50-200 2.8-4, which is equivalent (but 2x the price), but maybe a bit better optically? Or not?
Great review as always, Gordon. I own a Canon C70 and the EF 100-400 ii including the 2x extender. It's such a heavy beast and I consider to get the RF 100-400 but I wonder if this cheaper lens can compete - especially if we think about the crop. What is your advice? Sell the EF-version or training in the gym to lift it?
“Steven Seagull” (/Seagal) - quite funny. Your Brighton variety needs to gain some girth for a fair comparison. I must say that although British and Danish wildlife mostly look extremely similar, your starlings do look a little different. (And a lot like Carrion Crows, I think. But I’m not telling you anything you didn’t already know). Actually there IS (or was) one non-L lens that DOES (or did) come with a lens hood. But according to Canonrumors it’s now discontinued, although it wasn’t released until 2017. …oh, which one, you ask? The EF-S 35 mm f/2.8 IS STM Macro. (And it isn’t a traditional lens hood because it also serves as a filter adapter).
Great review as usual. Am still on my old Mk1 100-400 EF L adapted lens. The weight savings on this lens are enormous, so would love to know how the optical quality on this RF100-400 lens compares against that old glass. Does newer manufacturing techniques alongside the access to greater stabilisation make this lens a good choice without major compromises on the R5 or does that L glass still trump this cheaper and lighter alternative? Any thoughts?
I've not got any test images with the Mark I EF 100-400 to compare so it's hard to say. I feel your EF version will be higher contrast and of course better build.
@@cameralabs Thanks. It is hard to justify dropping money on every new lens - the new RF L glass is so expensive and hard to justify. Got to choose upgrades carefully.
@@ianflint4610 Having used neither lenses (but some Canon glass nevertheless) I'd suggest: 1. Renting the new lens to compare them for **your** intended uses. This should tell you which lens you prefer working with! (note: hand feel is also VERY important, and never mentioned in ANY review) 2. Looking at your use of the lens. Do you really need/want that little extra from your glass? Or would the small loss in quality be worth the massive drop in weight?
Background: So far, I've personally found that most lenses perform great under perfect weather conditions. And since I usually go hiking in the mountains to take landscape pictures, I don't really need glass that's better under bad lighting circumstances since, if the weather is bad, I never go up (or take out my camera) in the first place anyway... I got started with the Canon 15-85 and upgraded to the Sigma 18-35. I love the flexibility of the Canon lens and the quality of the Sigma. I also got the 50 f/1.8 and the 70-300 IS USM. I basically NEVER use those, so effectively they were an expensive way to learn the lessons I wrote above, lol. Similarly, although I'd LOVE to have the Canon 5R with the 24-70 and 70-200 lenses, I **know** that it would be a complete waste of my money, and that it is MUCH smarter to spend that money on more vacations than on extra gear... Okay, ranty tangent over 😅
Isaved up for the 100-500 L last christmas but it was never available here in Switzerland, always out of stock and huge backlogs on the major retailers, so im still waiting and it doesnt look like its available here anytime soon, definitely not this year anymore. If i didnt already save up for the 100-500 L i would definiitely "shoot" for this one, it does look mighty attractive. I still dont understand why they didnt build the 100-500 so that you can use the Teleconverters across the whole range... they can clearly do it (as seen here)...
This 100-400 lens and the 100-500 lens are completely different optical designs. It doesn't make much sense to say that just because this 100-400 can use a teleconverter for the entire zoom range, that the 100-500 should be able to. The RF teleconverters work by mounting a magnifying lens element deep into the back of the lens they are attached to. In the case of the 100-400, there is open space there which is never occupied by floating lens elements. In the case of the 100-500, when zoomed to 100-300, there is no such empty space; rear floating lens elements occupy that area. Thankfully the 100-500 engineers designed the lens to not even allow zooming out wider than 300 when an extender is attached, otherwise you'd be crushing internal lens elements into the front of the extender.
Crazy that it has no lens hood, and no weathersealing. I guess you only use it on dry, non sunny days, lol. Cheers Gordon, your reviews are always thorough.
Weeeell, I think most of us used many cameras on wet days without issue even though they weren't officially weather-sealed. In fact I've never owned a properly weather sealed camera in my life.
Thank you very much Gordon!!! Very good review. I'm shooting Sony, so the affordable long telephoto comes from Tamron or Sigma, also with the Sony 70-350 (yes, I'm shooting apsc), but this lens come at a price of 1000$. I think that Sony starting to lag behind the Canon in this regard....
I own an R5 and see no reason not to consider this lens versus one worth 4x the cost. Just because I was happy to spend a reasonable amount on the R5 body doesn’t mean I am willing to spend L glass money for every other lens I own.
Nah. I can comfortably hold my R5 with this lens one-handed for an extended amount of time. I would NOT be able to do that with the EF 100-400 (mark I) I own, or the 100-500 for that matter. For my use, the RF 100-400 is ideal.
Great content as always Gordon. Just moved to the R system and cant make my mind about what lenses to pair with my R8. Do a bit of everything. I'd appreciate your 2 pennies
Sweet, have been waiting on this. I’m a little bummed that the extenders made an appearance in the video, but we didn’t get any test shots (unless I missed it)!? That’s what I was looking for. I purchased this lens recently as a cheap-ish way to try birding. I’m enjoying it, but I wish it had a bit more reach. I’ve been debating returning it and getting the 100-500, but that’s still out of stock everywhere.
Coming from M4/3's, I’m surprised at the mediocre IBIS of Canon full frame cameras. I wonder how this lens would pair with the new R7 crop sensor camera? Your reviews are quite concise.
Another quality review! For those cost-conscious shooters looking for sharper optics/brighter glass, would you recommend adapting the Canon EF 100-400mm f/4.5-5.6L IS USM Lens to an EOS R body? Or do you see the choice as between this lens, the EF MkII or the 100-500 f.5-6-7.1?
I don't have results for the Mark I EF 100-400, but the Mark II is very good, definitely a step-up overall, especially in build, aperture, contrast etc, but obviously a LOT pricier and heavier.
If someone had the option between buying this or a 2x extender for a 70-200 F.28 L IS which would be better at 400mm? The 70-200 would be at f5.6, I believe.
Would you say this is just as sharp as the RF 24-105 F4l? I shoot landscape with the Canon R. As much as I loved renting that RF 100-500 it is just so expensive.
great review as always i got 2mm of ruler on my M50 sensor with the sigma 100-400mm......................used two x2 converters and a few ext tube too though :P
Gordon, would you say that this has about the similar performance of the older 75-300 zoom? I had one several years ago that I used taking pictures of my grandson at his early soccer games on my 60D, the pictures were great. But lenses always seemed to be loose if your wriggled the lens much, picture were always good. I had a 100-400 L version 1 for a long time, but it was a little too heavy and I sold it when I got my EOS R. Thanks for the great reviews! You have become my “trusted” reviewer!
Great lens review. I just got the RP and I'm trying to decide if I want to sell my sigma 50-500 for this... I'm waiting on the lens adapter to see how the Sigma performs.
I’d be curious to see a comparison in image quality between the rf 100-500, the new rf 100-400, and maybe the ef 100-400 ii. See if the image quality is that much better for the price. Heck you could even through the converters on and see how they all stack against the 600mm f11 and 800 f11. A super telephoto showdown.
depends on what you're using it for. me personally i'd rather take that god damn rf 100-400 and burn it to the ground in a pot of boiling acid and set fire to the damn thing and burn it to a million pieces then ever use that monstrosity one more time. the 800 f11 has been a dream. i've taken so many fantastic moon photos with it everyone's jaws drop from sheer amazement at how good the moon photos are. i've never tested the 800 on wildlife as i'm afraid of taking it anywhere in public where it could get damaged. the ef100-400 ii doesn't oversaturate the pictures like the rf100-400 does the ef100-400 is almost like the ef70-300 just shorter on the reach and slightly not as sharp as the ef100-400 but not by much very unnoticeable. But i'd rather jump headfirst into a burning building then ever work with that god damn rf100-400 again
I wish it had a weather seal and a tripod mount. I suspect they didn't include these features to keep some distance from this lens and the 100-500 L lens. Otherwise this seems to be a no brainer for anyone on the EOS R system not looking to spends a couple thousand on glass or size/weight constrained.
Hi Gordon, thanks for all the reviews + technical explanations. It has been very useful for me to move a level up. Just wondering which one would be good rf 600 or this one, I already have rf 24 to 100 (R6 kit lens) ? I know it is my decision in the end. but just wondering I want to shoot wild life and birds. Would f11 be limiting ? mostly will be roaming in Scottish wilderness - low light :).
depends how far they are and how happy you are to crop in on an image with the 100-400! The zoom would certainly be nice for extending your overall range from 24-400. If you're shooting in v dim conditions, it will get noisy at f11 on the 600 and 800.
Another great review. Thank you Gordon. I have a naive question about weather sealing. Both RF extensors are weather sealed. If you use one with the RF 100-400mm lens would the extender provide the same protection for the body, at least at the connection, as the weather sealed L series RF lenses? Logically it seems it would; it also seems logical that Canon would produce L quality extenders for L series lenses but that does seem to be the cases. My RF 24-105mm f4 L and my RF 70-200mm f4 L are not compatible with the RF extenders. Only my RF 100-500mm f4.5-5.6 has limited compatibility with the extenders, which frankly baffles me.
In terms of quality and if money wasn’t a primary concern.. Would you recommend this RF lens or adapting the older ef 100-400 4.5-5.6L IS ii? I’m shooting on an eos RP at the moment.
It'll be a downgrade in brightness, build quality and possibly rendering / overall sharpness. This lens is a quarter of the price, it's a budget option for people who can't afford an L version or don't want the weight of it.
I've got the Tamron 100-400. Originally bought for my Canon 6D Mk2. Should I get the RF100-400 for my Canon R6 and sell the Tamron? Is it worth it to swap?
Thanks for the great info. I recently moved to a R6 from RP for better autofocus. I’m currently using an EF 100-300L IS USM. Wondering it by going to the native RF 100-400 I’d be gaining autofocus speed/accuracy or losing IQ over EF lens?
Just wondering if this has any of the same issues as the RF 24-240mm, where the RAW photos are badly distorted out towards the edge, but the in-camera processed jpgs don't?
Most lenses use digital profiles to correct for geometry, so if you shoot RAW, your software needs the profile to correct the distortion. Adobe is sometimes slow at releasing these, but they do come. As for the 100-400, it does have a profile, but the distortion isn't as bad as the wide lenses.
As someone who already owns a 70-200 F4, would you pick this lens, or the 70-200 plus a 2x teleconverter? (assuming pure image quality is the only factor)
This is a budget lens vs the 70-200 being an L lens. I'd say the 70-200 should be better optically even with a TC. But the AF on an EOS R body will probably better with native RF
I've got a EF 70-200mm f/2.8 L IS USM mk 2 lens. I'm wondering if a RF 100-400 f/5.6-8 lens will take better pictures at 400mm versus my 70-200 f/2.8 at 200mm with a crop. Thanks in advance.
That's a tough one to answer without them side by side. The EF 70-200 2.8 II is a superb lens and definitely sharper than the 100-400, BUT cropped you will lose a LOT of detail. You can simulate it by downloading some images from my review of the Rf 100-400 and RF 70-200 2.8 from my review pages at cameralabs.com - there's links in the galleries to my original files - then you can see what you're left with after crops. A lot will depend on the camera body. An R5 will obviously leave more pixels than, say, an R6.
Sure, it's dark, but it's "cheap" and light and sharp edge-to-edge. Just about everything you could ask for in a consumer telezoom. I'd probably call this kind of lens a ~sine qua non~ for camera system to a lot of people. Without an affordable telephoto lens like this, there's probably a bunch of folks who'd never even consider getting into the system.
I'd base that on whichever body you prefer to use. The R5 should be better for video and photos, but you may prefer the style and size of the Fujifilm.