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]
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[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 propeller 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 propeller 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.

 

[21limited]

This is what happens when photgraphers think they understand humna perception, most don’t. Neurolgists do though.\
" 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”."

That may be the scientific truth, but it’s not the “human truth."

In my photgrpahy classes I used ot had my stuents a K-1000, show them how to take the lens off and release the shutter.
Startiing at 1/1000s , no one can tell what the shutter opening looks like 1/1000s is not in the range of human perception. As the speed ishutter is lowered, the opening and closing shutter becomes more and more visible. The actual time needed for an object to be visible to a human, is 1/00s. And as any of us birders know, 1/100s can produce motion blur. So we do see it. We do see it, and it is part of our reality. We are so used to seeing it looks natural in our photographs. Bottom line, if you had an object flash in front of your face at high speed and it move 6 inches in 1/1000s, you won’t see it. True you won’t see motion bl;ur but you won’t see it at all. Try watching a bullet sometime.

But the funny thing here is,
"if you use a high enough shutter speed you won't get any motion blur.” True, but given a fast enough object, you won’t see anything at all. SO that statement is both misleading, and inaccurate. And motion blur does exist in the realm of human perception. Just not in absolute scientific terms. Motion blur exists for humans, that’s all we need to worry about. Motion blur exists in two places. The camera sensor, and the retina of the eye. The extent of blur depends on what is capturing the image. That doesn’t make it a lie.

For the math guys, the limit of movement in a shutter speed of 1/infinty is no movment. But that doesn’t negate the fact that if your shutter speed is 1s, there will be considerable motion blur. Both ends of spectrum are part of the equation.

Bottom line, if you are a human, motion blur exists. If you are a camera capble of shooting at 1/infinfity, it doesn’t.
But of ocurse, then you have to concede, shutter speeds of 1/infinity don’t exist, so in the real world, motion blur does exist.

 

[Rickbb]

Back in the old film days, long exposures were about the only way to get a decent fireworks shot. But it was always a balancing act of how much was enough and how much was too much.

 

[Golem]

Represent in your pix whatever the motion represented to you. Forget about the math.
.

 

[MontanaDave]

1/60 second shutter speed

 

[21limited]

Love it…..^
Motion blur exists whenever the subject moves faster than the shutter speed can freeze it. To produce it at /1/000s, you just need a faster moving object.
2013-07-02-Red-Squirrel by Norm Head, on Flickr

 

[Politically Incorrect]

1/2 second

 

[21limited]

Amazing how something so useful doesn’t exist…..
2019-08-20-Nipissing-waterfall by Norm Head, on Flickr

 

[480sparky]

You don't need a theoretical 1/∞ shutter speed to 'freeze' motion. You only need a high enough shutter speed to prevent the subject's light from moving from one pixel to the next on the camera sensor (digital) or another crystal of silver halide (analog).

 

[21limited]

The fact that you can prevent motion blur doesn’t mean it doesn’t exist. That was the topic.