Is video a good alternative to low available light photography?

Question

I took a slow zoom and my mirrorless to a birthday party at a local kids' gym not knowing the light situation. It was dimly lit, and needless to say, the slow zoom + high shutter speed to freeze motion (at least 1/160 and often higher) required very high ISO, which my camera is not good at. I really wished I had enough money to buy a fast telephoto prime for a moment.

But then, there was the saving grace of this consumer mirrorless camera: the video! I don't take videos often, but one thing I knew was that the optimal shutter speed was 2 x the FPS of the video. My camera's video mode was set at 25FPS, which meant I could use 1/60 (since there is no 1/50 on my camera.) At 1/60, the camera didn't need to boost the ISO to over 800 that it needed for 1/160 or 1/250 for still. When I checked the results back home, they were not bad. Between the grainy ISO 1600 still and the video, the video had better quality and better capture of the fun of the day.

I understand that photo and video are not substitutes; they are complements. But if you can get better video under the given low light situation than photo, why not shoot video instead? I did some google search afterward, and haven't found any advice along these lines. I wonder why.

Answer 1

If the result you are looking for is a photograph, the short answer is no. The same equipment won't give better results with video than it can with stills.

I think the apparent difference is due to exactly one thing: resolution. Try taking one of your still frames, resampling down so it's 1080 pixels tall, and then comparing.

There isn't any inherent low-light quality advantage in the way video is captured — in fact, it's really much more limited. But lower resolution hides many faults. Noise will be less apparent, but it also can hide motion blur — for example, from the longer shutter speed that you used for video.

Correspondingly, when inspected very closely, the still frames may seem bad, but if you actually make prints — especially relatively small 4×6" prints, but probably even larger ones — they'll look surprisingly good.

As @jrista notes, if you're not looking at single frames of the video but are watching it, motion plus our brains equals even more concealment of flaws. But, not so good for framing and hanging on your wall. Don't underestimate the power of that. While Youtube and the like make it easier to present short videos, maybe for sharing with grandparents and far-away friends, unless you put the effort into producing an actual film, the video file is likely to be forgotten, possibly dusted off for a graduation party or wedding reception video, but mostly not remembered. A photograph, though, can be an heirloom.

Answer 2

How about a big old it depends. If video is what you want/can use then yes. Because while the video has a ton of blurring and focus issues (which you would have also had shooting stills), it also has a single large advantage -- a massively powerful image analyzer -- your brain.

You brain will merge frames, follow motion, and forgive much more than it will when you stare at a single still frame. If you stop and print a still of the video it will not compare with a still you could have shot at the same time, but if all you present is video, your viewers will do much of your post processing for you.

That all said, you are not going to get great quality HD video with great focus and composition without a ton of practice and post processing video is painful when compared to stills.

Answer 3

Video is much much lower quality than photos and has two things that make the noise seem less. First, it can trade resolution for noise management. Averaging the data from multiple pixels results in more signal per averaged pixel and random noise tends to cancel itself out, thus it is very similar to having a larger pixel that can collect more light. (This is also why Full Frame cameras do so much better in low light due to the larger photosites.)

The other advantage is that it is moving and thus the noise averages out over time as well. When you are watching a moving video, the random noise changes from frame to frame and the brain blends it together as another level of averaging to form a consistent image that is relatively noise free. If you took any individual frame however, it wouldn't be any less noisy than an averaged down copy of the still image with the same shutter speed.