If you do not have a camera and if videography is your priority, the answer is straightforward: go mirrorless, also called MILC (Mirrorless Interchangeable Lens Camera)!
What are the main differences between DSLRs and Mirrorless systems?
A DSLR (Digital Single Lens Reflex) is a camera based on a decades-old, time-tested constructional principle. Thanks to the mirror reflecting the image into your bright and large optical viewfinder (thus the R = Reflex), you always see what your lens sees. A huge advantage to stills photographers.
The body of a DSLR thus always needs to be bulkier than a mirrorless camera. The mirror takes up space. DSLRs are the direct descendants of SLR film cameras that stills photographers have been using since the 1950s.
A DSLR camera is designed and optimised for stills photography. Video is an afterthought for these cameras. If you think about it, the answer is obvious: the mirror stands in the way of light, so with an SLR you’re either looking at your scene through the lens OR you’re taking a picture, in which case the mirror flips up and the shutter opens and closes. It’s one or the other.
Shooting Video requires using the Live View
Video demands that you shoot continuously, many, many frames per second for minutes and hours. That means that in order to shoot video a DSLR needs to enter what is called the Live Mode or Live View. The mirror flips up and the shutter opens so that light could fall onto the sensor continuously.
When shooting video, you no longer see anything in your optical viewfinder! Your image appears on the LCD display of the camera.
Mirrorless cameras have revolutionised the market in the past couple of years.
They are smaller, lighter.
Their viewfinders are electronic which means you can use them while you’re shooting video.
Many of their displays offer tools for videographers that DSLRs can’t even dream about. Zebras, waveform monitors, focus-peaking, live digital zooms…
They have surpassed DSLRs when it comes to their auto-focus capabilities for video. (This is a fast evolving field, so nothing is set in stone for too long. But if you want object and face-tracking, that’s a mirrorless camera these days.)
If you’re starting out and considering buying a camera, I would recommend three brands today: Sony, Lumix or Fujifilm.
With Sony my recommendation would be something in the A7 range (currently the A7 Mark III or the A7S Mark II). With Lumix the obvious choice is the GH series (currently the GH5 and the GH5s). And with Fujifilm the best option at this time is the X-T3.
What if I already have a DSLR and don’t want to spend on an entirely new system?
Most current Canon DSLRs offer video capabilities that range from the decent to the excellent. The same applies to high-end Nikon DSLRs (the 7xxx range and full-frame Nikons) but I would warn everybody against using an entry-level D3xx or D5xxx for video. Those cameras are decent little stills cameras, but are simply do no meet the requirements for any serious videography.
If you want peace of mind, just read the previous entry that sums up my thoughts on buying a camera system for videography.