8/31/2023 0 Comments Motion blur editing![]() To calculate the Laplacian, you can use the imgradient function, which returns magnitude and angle, so we'll simply discard the angle: = imgradient(origIm) Which gives us the following images to start with: MuchBlurredIm = imfilter(origIm,fspecial('motion',20,45),'replicate') LittleBlurredIm = imfilter(origIm,fspecial('motion',5,45),'replicate') You usually wouldn’t want to expose 24 fps film with a shutter speed of 1/24 th of a second, because the blur would be too much, and the streakiness or ghostly images we mentioned would start to appear.Preparation: we read the cameraman image, which is often used for visualizing image processing algorithms, and add some motion blur. There’s also slightly more blur in 1/48 th of a second than in 1/60 th of a second, so the overall effect makes cinematic movement feel very different from that “live” feel of 60 fps video. This means the frame rate and the motion blur aren’t exactly matched, and the effect is a different feel of motion. While the shutter speed of video generally matches the frame rate, and each video frame is exposed for its entire duration, with film, that’s not usually the case. With film, each frame is usually exposed for half of its duration. In other words, a frame which lasts 1/24 th of a second is exposed for 1/48 th of a second. That accounts for most of the difference in motion between film and video, but there’s still another factor. First the frame rate is slower, so instead of 60 movements per second, we’re only seeing 24, leading to a slightly more staccato movement. Yet, it still appears to be natural, pleasing movement.Ĭinematic movement is a bit different from “video” movement in two important ways. It’s not the “live” look of video, it’s definitely something more surreal, not like what we see with our own eyes every day. This is the look we associate with film, with movies, and TV dramas. The other kind of motion we’re accustomed to is cinematic motion. The movement looks strange to our eyes, and though we may not be able to place exactly what’s wrong, it’s the absence of blur making the movement seem somehow harsh or unnatural. ![]() The same effect happens in video footage taken at a fast shutter speed, so fast that moving objects have no blur. But as they have done so, the movement in stop motion sequences has begun to look much more natural. It was a matter of process. No motion blur meant unavoidable choppiness in the movement. Only fairly recently have stop motion artists begun to add digital motion blur to their images. You’d see choppy stop-motion animation in the cheapest of B movies and in the most expensive of blockbusters. Without a motion blur, the movement looks choppy and artificial. When played back at 24 fps, the individual frames made up a full-motion sequence.īut there was always a problem. Because each frame was exposed as a still image of non-moving objects, there was no motion blur. They would continue changing the scene and taking frames until they had created their entire sequence. They then manipulated the scene, changing only a very little bit, and took the next frame. Stop motion artists created a physical scene with models and puppets, then took a single frame of film. Imagine old-time stop motion effects, a time-honored filmmaking technique. The amount of blur makes a difference in how we perceive motion. By contrast, a very fast shutter speed may expose so quickly that even quick-moving objects have no blur at all. A slower shutter speed exposes for a longer period of time, so moving objects move further than they would with a faster shutter speed, and they blur more. ![]() In photography and video, motion blur is a function of shutter speed, the length of time the camera iris is open and exposing. It happens because objects move during the time it takes to expose the photo or the frame, and the movement gets recorded as a blur. Motion blur is the blur seen in moving objects in a photograph or a single frame of film or video. ![]()
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