My daughter is jumping horses and getting pretty good at it. Currently I’m shooting a Nikon 850 with a 70-200 2.8 and of course it gets fantastic stills.

But video is really helpful for her to see what she’s doing and what to work on. The 850 is honestly pretty awful for video when the subject is in motion. And I cannot stand using the back panel for video.

Mirrorless seems the perfect application for this. Are there models out there that can get a high quality still WHILE shooting video?  I would want interchangeable lenses and an electronic viewfinder. I’ll need something in a 50-300mm 35mm equivalent focal length at the distances I’m shooting. Low light capability would be nice, but she generally rides outdoors with plenty of light, so I only need to keep noise down while getting stills that freeze the action. > 60fps might be cool to make slow mo’s.

Ok ARFCOM, do what you do: spend my money.

I would get a video camera for taking video. Using a picture taking camera for video is like hunting with a 3 1/2" 12 gauge. You can, but clunky and awkward.

DSLR and mirrorless full frame cameras can indeed fill all but one of your needs... kicking out a still image (of sufficient resolution to make a print from) remains the providence of something like a Red Cam. Big bucks in other words.

People are in love with the video from the Nikon Z6/7II series, check those out. You can still get a frame from those but at best it will be a cinema 4k image - which is only about 9mp and may not be as clean as a still image even from the same camera/sensor.

The trade off is that a DSLR can have much better lenses than a video camera in the same price range.
Lens quality > megapixels.
Usually (professional) video cameras have better audio options.

Thanks for the replies.  I'm going to look into Nikon's Z series partially because I can use my F-mount glass with the FTX adapter which appears to be included in a lot of packages from B&H.  I think that the Z will do still captures but not at full rez.  I'm also coming up to speed on "slideshow" effects in the viewfinder and how much that sucks on action shooting.  There may be no silver bullet in this situation other than having a second person do the video with a different device.

Using a basically still camera for video camera will yield only adequate results, for me I use Nikon D7500 for video for concerts and the likes at my local HS where I just set the camera on a tripod  and record, nothing all that serious; the results are good enough for me, I shoot at 60fps. Now if you have to do power zooms etc a true video camera will probably get better results. I use my Sony A6600 for stills because it has a noiseless electronic shutter.

I have a fixed-lens Sony RX10-4 & RX100-7 with a that has a 1" sensor(this sensor is smaller than a APS-/DX sensor), that can do BOTH videos and stills at the same time, but the stills are only standard resolution.