R7 vs R6 Mark II: Best for wildlife photography and lens compatibility

[cem421]

I currently have a Canon T7i with EF 18-55 mm and EF 55-250 mm lenses, and a Sigma 100-400mm f/5-6.3 DG OS lens. I mostly am focused on wildlife photography and occasionally landscape as well (think hiking photography). I'm looking to upgrade to mirrorless and have been looking into the R7 or R6 Mark II. I've looked at both in person and like the features (low light, autofocus) and feel of the R6 but don't know if I want to risk losing the reach with a full frame camera - plus I don't know if my Sigma lens would work well with the R6. My hesitation with the R7 is I've seen the autofocus isn't the best but it's a better option for wildlife. The price difference between the two isn't really a factor for me - I'm mainly concerned with the quality of the images, being able to continue using my Sigma lens, and the longevity of the camera.

[deebatman316]

When EF-S/ RF-S lenses are used on Full Frame EOS R series cameras. The camera automatically switches to APS-C/ 1.6x crop mode. It cannot be switched back to Full Frame mode. Also there will be a significant reduction in megapixels. In Full Frame mode the EOS R6 Mark II has 24.2 megapixels. But in APS-C Mode it only has 9.5 megapixels available to use out of the Full Frame sensor. This is because the lens cannot provide an image circle large enough to cover the entire image sensor. The EOS R7 will not have this issue as it is an APS-C camera. So no such cropping is needed. The EOS R7 is quite finicky about 3rd Party lenses. Some lenses work fine others will have compatibility problems. If you plan on adapting lenses. Not all lenses are fully compatible with the EOS R series cameras. Especially the highly advanced AF system features or high fps in H+ shooting mode. Full and complete names of lenses are needed to determine compatibility. When adapting lenses stick with the Canon brand adapter. 3rd Party Mount adapters cause nothing but trouble. I always highly suggest renting the camera body in question. To see if your 3rd Party gear will work. Instead of finding out later that it’s incompatible when you already purchased the camera. I have posted example lenses below to help correctly identify your lens.

 

[cem421]

Thank you for the information, it was really helpful! As mentioned in my original post, the lens I'd be looking at continuing to use is my Sigma 100-400mm f/5-6.3 DG OS lens (this is an EF lens). I would not be looking to use either of the base lenses from my Canon T7i.

I'm also open to other camera model suggestions. I've just found in my research that the R7 and R6 Mark II are the most recommended for what I want to do.

I've never heard of renting cameras before - I'd be curious to know more about this.

[cem421]

In my research, I've located additional information on my Sigma lens. It is in fact a full frame lens. With this information in mind, I'm curious if the R6 Mark II is recommended for the type of photography I'm interested in.

[deebatman316]

Yes the Sigma lens mentioned is a Full Frame lens. Some Sigma lenses have compatibility problems on EOS R series cameras. So always check before buying a new camera. Some older Sigma lenses have a problem where IS and AF fight each other. Other lenses have problems with IS and IBIS fight each other. 
Sigma                    Canon
DG = Full Frame    EF/RF = Full Frame

DC = APS-C          EF-S/ RF-S = APS-C

DN = Designed for Mirrorless  RF/ RF-S = Mirrorless 

OS = Optical Stabilization  IS = Image Stabilization 

HSM = Hypersonic Motor  USM = Ultrasonic Motor