Join Mark Christiansen for an in-depth discussion in this video Recognize and fix rolling shutter distortion, part of After Effects Compositing 03: Advanced Matching and Looks.
Here we are looking at a rather dramatic example of what is known as rolling shutter distortion. It's also called jello cam. And the reason for that is that it leads to this wobbly appearance in what you know should be straight up and down lines in an image. You see it when you get fast, particularly horizontal motion and the image is shot with an active pixel sensor camera. So, this is also known as a CMOS camera. I'll just stop that cuzwe don't want to get sea sick. And a CMOS camera scans the image from top to bottom. So it will have the side effect of a lag between top and bottom.
Or sometimes from bottom to top. The cure for this is the Rolling Shadow Repair effect. This is found under the Distort menu. And I'll just apply that here. So on a frame that has Rolling Shutter Distortion, you can see that what this effect does, is actually analyze the image for that distortion and correct it. Now, we're not quite going straight up and down here and in fact we see the distortion kind of reversing here. So we haven't totally solved it here. If that's the case, you can raise the rate and that will straighten it out more.
But I still see an unpleasant side effect here. So in this case, I can also switch from the Warp method, to the gentler Pixel Motion method. And lower this back down, now we're back to straight again. Now, you can still see that it's not perfect, but if we watch the whip pan in full motion, it may be good enough. The best solution here would be to just not shoot it this way in the first place. You could do the pan more slowly and add the motion blur in post. But this may be good enough.
A separate case where you can see Rolling Shutter Distortion is when you're either in or shooting a vehicle passing by. So here it's not so noticeable that there's Rolling Shutter, but you can see the lines are a little bit diagonal. And if I apply Rolling Shutter Repair here, you'll see the difference between when it's off and when it's on. In this case however, the effect has a little bit of problem because it can't really very well distinguish this car passing by from the background scene. And so you see extra distortion that's actually been added to the scene, there to the right. Now, in this case switching to pixel motion helps a bit, but you still see some unpleasant side effects.
So in this case, I wouldn't recommend using Rolling Shutter Repair at all. The simplest way to avoid Rolling Shutter artifacts, is either to avoid shooting fast motion and particularly horizontal motion like this. But, if you know if you'll need to shoot a moving vehicle or from one, it may be best to choose a camera with a CCD sensor, that doesn't create these kind of artifacts.
- Advanced color correction with multiple objects and Curves
- Adding a light-wrap effect to composite into a backlit scene
- Compositing into lens distortion
- Recognizing and fixing rolling shutter
- Matching motion
- Working in HDR
- Create cinematic color contrasts with Mojo
- Customizing a film look with Looks