Motion Blur is a Lie

[VidThreeNorth]

I don't think anyone has actual said this before, because nobody cares: Motion blur is a lie. It is a photographic lie. Most of us like it, and we use it, but, yeah, it's a lie. If your eye was good enough in the situation, it was not what you would have seen. That is why, if you use a high enough shutter speed you won't get any motion blur. The first time I had to face it was when I started recording video, because in videos it became obvious that from frame to frame, an object can move and you can see it sharply in different places. But this is not what we generally want, so we slow the shutter speed to get the motion blur. Actually, now (for video), I'm sort of ambivalent about it. I'm just as happy seeing an object in motion sharply, frame to frame. I don't "need" motion blur. I'm perfectly happy seeing the "truth". On the other hand, for "still" photography, I still feel that motion blur has a function, because you cannot see the motion without it.

Anyway, this video is what brought this issue to me:

"Samsung Galaxy S23 Ultra - Must Have Camera Accessories!",
posted Jul 8, 2023 by "Steven Divish", [Length 11:20]
""

 

[AlanKlein]

For video it's recommended you set the shutter speed for video double the frame rate. That's known as the 180 degree rule. So for example, if you're shooting 24fps, set the shutter at 1/50. For 30fps, set it at 1/60. At 60fps, set it at 1/120. Setting the shutter speed higher or lower can create weird movements, jumpy, or too smooth.

What is the 180-degree shutter rule when shooting video?

As a general guide for normal shooting conditions, the 180-degree shutter rule says that your camera's shutter speed should always be twice that of the frame rate when filming video.

camerajabber.com

 

[wfooshee]

The big lie for me with motion blur in photography is fireworks! People purposely shoot 1/2-second or longer exposures to get streaks of light that look like flowers in the sky. Personally I hate that! It's not what fireworks look like! I guess it's a nice artistic effect, but when that's all anybody does, it's not an effect any more.

I make an effort to shot fireworks to present them as they look while you're watching them. This one is 1/250.

OTOH, motion blur absolutely imparts a sense of speed. How boring would this shot be without the blurred background and wheels?

Maybe "lie" is too strong a word, as it implies complete negativity. In video, insufficient motion blur in the frames produces a stuttery effect, a literal series of pictures rather than a "movie." If you need super-slo-mo, though, you want a high frame rate and very short shutter speed so you do freeze each frame. In photography, motion blur either adds to the image or detracts from it. Which way that falls may be different for the viewer and the photographer, like the fireworks long shutter shots that I don't like. Many people love those, but they don't show what you see; an artistic effect, or a lie?

 

[petrochemist]

It's not a lie at all, just another way of representing things and one that can be much closer to what we see.
If you photograph a propellor driven aircraft at a fast shutter speed (faster than 1/1000) it looks like a static model.It's only when you slow down the shot enough for some propellor blur that it looks real.
The human visual system has a persistence of vision, which enables video frames to look like smooth movement. I contend that is nearer to being a lie, but it's not something we can alter.

Using shutter speeds a photographer can give a false impression of the degree of movement, often this is done with artistic intent - either freezing rapid motion or emphasizing motion.

Motion blur via photoshop may be a lie, but if it's done by shutter speed the motion has to occur.

 

[480sparky]

If motion blur is a lie, so are time-lapse, long exposure, flash, high shutter speeds, movements on a large format......

 

[VidThreeNorth]

It has been an interesting discussion. I thought back trying to remember where the idea came from, and actually (and not surprisingly I guess) I cannot remember.