How can I avoid lines when videoing a computer screen?
The reason for seeing the scan-lines in your example is your shutter speed is at 1/30 of a second, and the computer screen is refreshing at a different rate.Your shutter speed should match the computer's refresh rate as closely as possible. You can check your display preferences to see what the refresh rate is and attempt to match (I would start with a shutter speed of 1/60). You could also simply look at your screen / viewfinder and adjust the shutter speed until you achieve a satisfactory look. Keep in mind that as you adjust your shutter speed you will be adjusting exposure and need to compensate with a change in aperture or ISO. For example if you went from 1/30 to 1/60, you will have cut the light in half. This means you need to either open your aperture up a full stop (if your lens can go faster), or you will need to bump up your ISO (from 100 to 200 in your example).Best of luck!
How do I beat the flickering caused by a light when recording a video?
LED panel lights and strips can cause this effect, especially cheap stage lighting. It's terrible because sometimes your monitor does not show it and you only realise when you review the rushes later. If you even suspect it, adjust your shutter speed until it improves in the monitor. This problem will likely get more common as LED's become more ubiquitous. There is no fix in post.Actually, it just occurred to me that the 'Neatvid' NLE plugin has a preset for flicker reduction using a temporal filter. Expect to lose a lot of sharpness in in the image though.
What would happen if you point a camera at its live feed monitor?
Wow finally a question I feel qualified to answer, I will not go into details about what will happen when you point a camera to a video screen. Others have answered this question very well.First I will point to my favorite video feedback video, the original Doctor Who intro:Second I will tell what happened to me, after having found out about video feedback: I got addicted.I just do it in the GPU of my computer.I use vvvv to create texture (video) feedback, essentially the same thing happens as with the camera + monitor setup but you have much more control, so by just rotating a rectangle and stretching and rotating the image (would be like stretching and rotating the monitor) you can get something like this:If you then add filters, like blur and edge detect to the feedback loop, you get infinitely more chaotic and complex results:In this work I sample pixel values from the diagonal of the image and transform them into sound, so what you hear is the diagonal of the video image used as an audio waveform.Working with video feedback is super interesting, especially once you begin to control it. So even though you might not have the tools to begin experimenting I can highly recommend making those experiments. It is very addictive, but an addiction I really don’t mind having.Sune PetersenMore feedback projects in my portfolioNB. also check out reaction-diffusion which is essentially video feedback with edge detect and blur in the loop, here used amazingly by Nobutaka Kitahara:This kind of feedback is not just happening between cameras and monitors, but also in nature: Fish patterns | Reaction-diffusion in nature and as always nature came first.
Why do videos filmed in 60FPS look weird?
Since the rise of film in the early 1900’s, every known piece of footage was filmed and projected in 24 frames per second (until the last 10–20 years or so). The human eye has been cognitively trained throughout the past 100 years to recognize 24FPS as the “proper” form of a moving image.Some backstory: when projectionists and filmmakers first designed and shot footage, they found that 23.91 frames per second was the MINIMUM number of frames passed through a projector every second that the human eye could perceive as a moving image (that is, without seeing every single frame as a single image). Thus, 24fps became the standard for film formatting.With the rise of digital technology and new camera capabilities, we started to see 30fps, 45fps, and yes, even 60fps being used more frequently. The reason this looks so odd is that almost every single television show, movie, home footage, and internet video is shot and shown in the traditional 24fps format. When we see 60 frames every second, our brain senses this motion as incredibly fluid and smooth, which is why videos in 60fps look so weird and surreal. Essentially, this all comes down to the fact that our brains are trained to recognize 24fps as “normal”; everything else just looks bizarre. Whether this will change as 60fps becomes the new norm is my question; will our kids look at 24fps films and say “wow this looks so weird”?
Why do I decide to be vegeritian?
because it makes you live longer
Why does a television screen flicker when you record a video of it when it actually doesn't?
Monitors and TV's typically have a set refresh rate - 50Hz and 60Hz are fairly common. This means that the screen is redrawn around 50 or 60 times a second. To the human eye, this looks smooth - it's fast enough to be almost unnoticeable.Cameras, though operate differently from our eyes. If the frame rate of the camera matches the refresh rate of the screen you're looking at, it'll probably look fine. Usually, this isn't the case. The camera then could capture a partly drawn screen as one of it's frames, and then capture a different part of the screen in the next frame, etc. Net result: It looks like it flickers (or you see moving black bars), since it does this very quickly.The flicker is caused by two things:1. A difference in the scanning frequency between the TV and the camera.2. A difference in the way the phosphor dots are perceived between the human eye and the camera's image sensor.The black bars are a slightly different story from the flickering - the issue there is called aliasing. It's the same reason why if you film a wheel moving at the right speed, it can look like it's spinning backwards. If you think of video cameras as just taking a lot of pictures really fast, the way we perceive motion in a video is that you assume things move the smallest amount possible. For example, if a wheel has 8 spokes (evenly spaced, 360/8 = 45 degree separation) and rotates 35 degrees between frames, you'll probably think it took the shortest possible rotation - 10 degrees in the opposite direction (this breaks down if the spokes are distinguishable). The black bars you make see on some cameras are the same effect - the camera captures snapshots at different points in time that make it look like the bars move in a way vastly different from the actual scanning of the screen.You should read this article for further information:http://electronics.howstuffworks...
When I record a video of a projector screen, why are there black lines moving across the screen?
Well... You need to make the frame rate of the camera an integral multiple of the refresh / projection frame rate of the projection being displayed. So, you need to know both. Note that frame rate and shutter speed are not the same thing. Film frame rates vary quite a bit. 8mm and Super 8 film used 16 or 18 fps. 16mm and 35mm use 24 fps. Video frame rates vary too. For conventional televisions and TV projection systems, PAL and SECAM systems use 25 fps, NTSC systems use 30fps (actually 29.97). Computer displays often use a variety of frame rates (from 50 to 240 fps, generally). LCD displays don't flicker like CRTs do, but if they use a CFL bulb and it's old, it may flicker at a frequency that doesn't match the display refresh rate.