The Usual Question

The question in question—see what I did there?—tends to lead directly back to some original RED camera marketing, where that company claimed that you could shoot stills and videos simultaneously with their cameras, and thus the DSLR was dead. I can't remember which RED camera this pitch first came up on, but in was somewhere in the 2009/2010 time frame if I remember correctly. 

What's the question? Well, given the Canon R5's 8K video capability: "Why can't I just shoot 8K video and just extract the best 33mp still from it?" 

A few things stand in the way of this being something we'd all do, let alone do all the time.

First, there's shutter speed. If you're shooting video you generally push your shutter speed down to an inverse of the frame rate (or as near as you can). In other words, something like 1/30 second shutter speed for 24P (24 fps) video work. You do that for exposure reasons and for video reasons: to get the maximum exposure on each frame; plus video at high shutter speeds doesn't visually comply with the century-old intraframe blur we expect, thus the results don't look cinematic. Push the shutter speed up and you're sacrificing the video look for the still look. Do the opposite and you get the opposite.

Next, we have rolling shutter impacts. If there's any motion (or frequency-based lighting) in the scene, we might get artifacts from that.

Then there's the issue of what constitutes a frame. In compressed video, a still frame is calculated from a base frame and compressed information about subsequent changes. With non-moving subjects, non-moving camera, and non-moving backgrounds, you're probably fine in extracting a "frame" from a compressed video sequence, but the post production work and gear necessary to do that aren't exactly trivial. Certainly, Hollywood has done this to create marketing images from films, and many videographers do it to create a master still frame to appear as the visual video placeholder, but still photographers are not running around shooting video to get stills.

Finally, there's the issue of file size. If you want to do this "right," you'd be shooting 8K Raw, and that's going to generate something over 400MBs per second.

One key reason why you wouldn't just extract stills from video is evident on the Canon R5 itself: it can take 12 fps stills when shooting it as a still camera (20 fps if you can use the electronic shutter; again, rolling shutter might impact your results). This is more than enough frames per second to let you make reasonable selections from a time sequence, and it uses your existing still photography workflow and nets you more bits in a raw file to work with, too.

So, no, I don't think I'll be shooting video to get stills from an R5. 

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