How to Choose the Right Camera for You
Since the Canon 5D MarkII (since supplanted by the Mark III and Mark IV) started shooting video and consumer camcorders started capturing 4K, the lines of differentiation between cameras, and for what purpose, have been blurred. What follows is my take on how to navigate your choices, and make the selection which will be the most appropriate for you and the kind of media you intend to capture.
The Challenge: Who is the King of the Mountain?
Most Mirrorless and DSLR cameras shoot video and many can capture UHD 4K or 4K DCI. these days, so if you are looking for a one camera solution that shoots still photos and video, these tend to be a good choice. DSLR cameras are designed for optical viewing of the image through your lens, and thus incorporate a mirror that must be "locked up" out of the way to shoot video. This requires a live-view feature, and an LCD screen to see what you are shooting. Mirrorless cameras, on the other hand, have no mirror to lock up and use live view by default. The Sony A7S and A7R series and the Panasonic Lumix series are both Mirrorless cameras that offer excellent options. The A7S/A7R cameras feature full-frame sensors; the A7S opts for lower resolution and larger pixels than the A7R series. Both cameras feature Sony's E-mount, so they can accept almost any lens out there with the corresponding adapters. The Panasonic Lumix series offers a wide variety of cameras, but the GH4 and now the GH5 feature weatherized magnesium bodies. In addition, the GH5 enables internal 4:2:2 10-bit recording. The MFT mount can accept many lenses with different mounts and, with the proper adapters, you can use a full-frame lens and keep the full-frame depth-of-field characteristics, while effectively doubling the speed of the lens.
Although there are a few consumer camcorders on the market that also take stills, the stills tend to be limited to 2MP, or sometimes are up-scaled to 10MP, so you won't get the 24MP resolution that still cameras seem to be aiming for currently. Of course, you could shoot video and pull frames in post, but remember-video is generally shot using a relatively slow shutter speed (about 1/50 of a second) and this provides motion blur to the image, which is good for making motion look smooth, but not so good for sharp photos.
Don't forget to check out the capabilities of the professional and Digital Cinema video cameras. These cameras tend to feature more choices for codecs and compression, the ability to shoot video using Log or raw formats and employ professional XLR inputs for audio. Panasonic, Sony, Canon, JVC, ARRI, Blackmagic Design, RED, and AJA all offer cameras worthy of consideration.
Still images are usually viewed for significant amounts of time, so artifacts and defects in the image can become quickly noticeable and distracting. Therefore, stills resolution is usually high, with most current still cameras packing 24MP sensors-far greater than even 4K UHD origination. Many still cameras offer the option to shoot video, as well, either HD or 4K. With their large sensors and interchangeable lenses, this is seen by many as an attractive option, but it is no slam-dunk.
Whether standard definition (SD), or High Definition (HD), or now 4K-video cameras have always made certain compromises capturing the image when compared to a still-camera frame. This often had to do with the fact that each "frame" of video is only seen for 1/30 or 1/24 of a second (in general), so artifacts and defects are gone almost before you notice them. This fleeting image is one of the reasons motion pictures and, later, digital images could get away with using smaller sensors and lower resolutions than full-frame still-picture cameras. With HD resolution, you are capturing just above 2MP of resolution, and 4K UHD is a little bit bigger than 8MP per frame. Additionally, with electronic/digital capture of frames with movement within them, there is a wide variety of techniques available that compress the images for storage and can trick the eye into seeing a sharp moving image that, when frozen as a still, doesn't quite look as sharp as you might expect.
Just like your cell-phone data plan, you don't get something for nothing and even though capturing high-resolution imaging isn't generally a problem these days, when you start recording minutes of video at 30 fps (1,800 frames per minute) this can take quite the toll on a camera. Even shooting at lower resolutions of HD and 4K when compared to still-photo resolution, there are many issues that can pop up, such as overheating and your camera shutting down, or dropped frames if your recording media is not up to snuff. Annoying enough when you are shooting your kids' grade-school plays-which they'll be happy won't be saved and shown at their weddings-this is absolutely devastating to a professional who must get the shot.
There is the matter of how you reduce a 24MP sensor to 2MP for HD, or less than 9MP for 4K. Is the camera binning pixels, or line skipping, or doing some kind of down-scaling in-camera? All these can lead to unwanted artifacts. Of course, you could crop the sensor, but then you are effectively changing the field of view of the lens you are using. Most video cameras, on the other hand, have smaller sensors, and are purpose-built to handle the data rates and heat that is generated when capturing video.
Stills cameras seem to have a few more refinements than a consumer camcorder, especially when considering autofocus capabilities. To match the interchangeable-lens capabilities of a still camera, video cameras generally cost twice as much.
All this may seem to point to a stills camera as a no brainer, but there is a reason video cameras have developed along the lines that they have. Looking through a viewfinder and balancing a camera on your shoulder for minutes at a time is much more effective than holding the camera in front of you, trying to keep it stable. Even consumer camcorders have a shape more conducive to the classic handheld style than a still-camera body. This does make a difference. Yes, you can get/build a shooting rig for your still camera, adding loupes and external EVFs, etc., but now the size and cost of your still camera starts to meet or even possibly exceed your purpose-built video camcorder.
I hope I've given you something to think about as you consider which camera is the right one for you. I've started gravitating toward the mirrorless side of things primarily for the small form factor; if I were shooting longer projects, my A-choice would be a Pro video or Digital Cinema Camera. Just remember-the best camera for you is the one that puts the fewest limitations on your creativity, and the best camera is always the one you have in your hand at that moment. What would be your choice? Tell us in the Comments section, below.