amfoto1 Loc: San Jose, Calif. USA

It's actually worse than that.

The R6 is a full frame mirrorless camera that uses RF-mount lenses.

Your T7i is an APS-C DLSR that uses EF/EF-S mount lenses.

It is possible to adapt EF/EF-S mount lenses to use them on the RF-mount camera. However, because the R6 is a relatively low resolution full frame camera, it's really not practical to adapt EF-S (crop) lenses. While they will fit and work via an adapter, the crop factor of the lens will not use much of the camera's available sensor. When you crop full frame down to APS-C size, as you'll be doing using EF-S lenses on a full frame camera, you "throw away" about 60% of the image.... so instead of a 20MP camera, you'll get an 8MP camera. Might as well just buy a 30D from 2005. You can get those cheap! (It actually isn't quite this bad... because you are mounting an EF-S DSLR lens with 44mm back focus onto a full frame mirrorless camera with 20mm back focus, via an adapter, the image circle of the EF-S lens will cover more than 40% of the sensor in some cases. But it will vary with lens, with zoom focal length and with lens aperture. So just use this as a rough estimate.)

If you were to buy an R6, you would do best using RF lenses on it. There's a new RF 100-500mm lens coming to stores soon that looks neat for wildlife photography. It's pretty close to the same size and weight as the EF 100-400mm "II", which is a great lens for wildlife, sports, etc. Of course, the new RF lens is 100mm longer, so should be even better. The RF 100-500mm will sell for about $2700.

For some wildlife, 500mm on full frame really isn't "long enough". If you plan to shoot small shy critters like birds, you also might want the new RF 800mm f/11 lens, which is surprisingly compact and affordable at around 3 lb. and $900. (Compare to the EF 800mm f/5.6 that's 10 lb. and $13,000).

In other words, unless you are prepared to "gear up" with lenses too... full frame and/or RF-mount... there's not much to be gained, and even a lot to be lost, switching to an R6.

Or, stick with the DSLR you've got. Thanks to it being an APS-C "crop" camera, on the T7i a 300mm lens "acts like" a 480mm lens would on full frame... or a 400mm lens "acts like" a 640mm would on FF... or a 600mm lens (check out Tamron and Sigma) "acts like" a 960mm on FF. There are still far more lenses available for the EF-S/EF mount of your T7i, than there are for the R-series mirrorless. And the lenses for DSLRs like your T7i tend to be a lot less expensive than the lenses for mirrorless, simply because there is a lot more competition and choice of lenses for DSLRs, keeping the prices depressed to some extent. A Canon EF 70-200mm f/2.8L IS USM III lens is selling for $1900 and there are three other Canon EF 70-200s, as well 70-200s from Tamron and Sigma, that all cost even less! In comparison a Canon RF 70-200mm f/2.8L IS USM lens for use on the R6 costs $2600 and so far there are no RF-mount alternatives from Canon or anyone else to consider. I'm sure eventually there will be more choice of lenses for the R-series cameras. But it's a new system, having just launched two years ago. In contrast, the EF/EF-S lens system your T7i uses has been in development for over 30 years. There are currently 15 Canon lenses for the R-series cameras... In comparison, there are 82 EF/EF-S lenses currently listed at B&H Photo... And there may be almost that many older models that have been discontinued and are available on the used market.

Some day there might be an APS-C R-series mirrorless camera that will be a great option for wildlife shooters. Right now Canon's APS-C mirrorless are the M-series, which they have really neglected. It's been around for 8 years, but they've acted like they were point n shoot cameras with a few interchangeable lenses. After 8 years, there are currently only seven EF-M system lenses, which can only be used on the M-series cameras (can't be adapted for use on DSLRs like yours or on the new R-series cameras). There really is nothing in the EF-M lens line-up that's ideal for wildlife, either. The longest tele anyone makes for them is 200mm. So it would be a matter, once again, of adapting EF or EF-S lenses for use on the cameras. While the latest M-series are nice cameras, they don't yet have the high performance AF system in the latest R-series. There is rumor of an M5 Mark II later this year or early 2021, that will see some significant advances. But it's just a rumor.... No one knows if it will actually happen or when.

What are you hoping to accomplish with the camera "upgrade"? If you are thinking about saving weight... the R6 is actually heavier than your T7i. It's also pretty close to the same size. If you were interested in the fancy new AF system in the R6, which I'm the first to admit appears to do some really cool things, well it's going to be an expensive trade-off to get it... Plus, you'll be giving up some other things.

My advice, stick with what you've got. If you really need an upgrade, consider the 90D. But it's ultra high resolution 32.5MP APS-C sensor demands top quality lenses... do you have those? I would not go with the T8i. It just isn't all that different from the T7i... similar AF system and both are 24MP. Most of the improvements to the T8i have been video related. Another thing, the T7i can optionally be fitted with an accessory battery grip, which can be handy when shooting with the camera in portrait/vertical orientation, plus adds a second battery, and can help the camera balance better with large telephoto lenses like wildlife photographers often use. There's no battery grip available for the T8i and it's not designed to accommodate one. That's a shame, IMO.

LFingar Loc: Claverack, NY

Not always. All of the R series bodies will still have full AF function with the 100-400 and the 1.4x. With my R, 100-400 L II and EF 1.4x III even AF speed was changed little, if at all. With my EF 2x III the AF speed is slower but otherwise I still have full AF capability with that lens.

bleirer

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imagemeister Loc: mid east Florida

Like I said, AF will suffer - maybe a little, maybe a lot .... - always - yes, they will "function"

Gladys

Thank you