<p>The problem with recording a video display with a video camera weather LCD, LED, or old fashion CRT is the frame rate often does not match the camera. Artifacts may include a vertical bar rolling through the screen. Even if your camera can match the frame rate of the display being recorded one may still end up with moiré pattern artifacts.</p>

<p>Many productions find it easier to either cut out the display and add by compositing and masking another layer for the desired content. Another way is to green screen the display area and use chroma key to add the additional layer of content in post production. Not everyone is great at setting up the perspective correctly in post. One needs a professional video editing software that has the ability to alter the added layer with track motion that has x, y, z axis controls. This is not a trivial task.</p>

<p>Other possible solutions may involve the use of gen lock and frame lock systems.</p>

CC BY-SA 3.0
2012-12-07T21:24:21.993Z
OK. I thought that LED or LCD pixels stayed lit all the time when they displayed a constant color, but I was wrong; I'll try by myself and see how it looks.
alecail
CC BY-SA 3.0
2012-12-07T21:39:40.193Z
By all means give a go to see what you get, at best I think you will see moiré patterns depending on the distance and focal length of your camera lens.
filzilla
CC BY-SA 3.0
2012-12-07T21:41:56.263Z
BTW: I was able to capture real time HDTV at home last weekend but the HDTV was only 1/3 in my field of view, but the trick was to bring the illumination down considerably to match a dark scene and to my surprise there were no moiré patterns. This video is not ready for release yet otherwise I would point you to a link.
filzilla
CC BY-SA 3.0
2012-12-10T22:29:49.030Z
FYI: Example where it worked, Low light situation where I was able to get my HDTV set to very low illumination with a camera shooting 1080i and rendered to 1080p here: https://vimeo.com/55295820 look at time makers 00:27 and 00:41 in this short video.
filzilla
CC BY-SA 3.0
2012-12-07T21:11:18.990Z
2012-12-07T21:11:18.990Z
filzilla
<p>I see this all the time: a character is doing something on a computer or watching TV. Instead of filming the actual content of the screen, they film the scene with a fixed camera and add a layer with the content they want to show during post production.</p>

<p>Here is an example (from a TV series named Underemployed, Season 1 episode 1 at 18:42). <img src="https://i.sstatic.net/hX76B.png" alt="screen changed at post production"></p>

<p>In this case, you can see that the perpective correction is wrong (the bottom right corner doesn't match the actual corner of the screen), and I'm really wondering what I'm looking at. It looks like a deformed iPad application displayed on a cheap PC, I really don't know.</p>

<p>What kind of problems occur when you film an LCD ? Is it a technical issue, or is there another problem I'm not thinking of ? Maybe a logistic problem (like.. the actor doesn't know how to use a computer, or they should synchronize the actors play with the content played on the TV..).</p>

<post-production>
Why not filming computer or TV screens?
alecail
# Why not filming computer or TV screens?

(Asked by: username_0 on 2012-12-07)

I see this all the time: a character is doing something on a computer or watching TV. Instead of filming the actual content of the screen, they film the scene with a fixed camera and add a layer with the content they want to show during post production.

Here is an example (from a TV series named Underemployed, Season 1 episode 1 at 18:42). ![screen changed at post production](https://i.sstatic.net/hX76B.png)

In this case, you can see that the perpective correction is wrong (the bottom right corner doesn't match the actual corner of the screen), and I'm really wondering what I'm looking at. It looks like a deformed iPad application displayed on a cheap PC, I really don't know.

What kind of problems occur when you film an LCD ? Is it a technical issue, or is there another problem I'm not thinking of ? Maybe a logistic problem (like.. the actor doesn't know how to use a computer, or they should synchronize the actors play with the content played on the TV..).

**Tags:** post-production


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## 1 answers

### Answer by username_1 on 2012-12-07. Score: 4

The problem with recording a video display with a video camera weather LCD, LED, or old fashion CRT is the frame rate often does not match the camera. Artifacts may include a vertical bar rolling through the screen. Even if your camera can match the frame rate of the display being recorded one may still end up with moiré pattern artifacts.

Many productions find it easier to either cut out the display and add by compositing and masking another layer for the desired content. Another way is to green screen the display area and use chroma key to add the additional layer of content in post production. Not everyone is great at setting up the perspective correctly in post. One needs a professional video editing software that has the ability to alter the added layer with track motion that has x, y, z axis controls. This is not a trivial task.

Other possible solutions may involve the use of gen lock and frame lock systems.

> **Comments:**
> **username_0**: OK. I thought that LED or LCD pixels stayed lit all the time when they displayed a constant color, but I was wrong; I'll try by myself and see how it looks.  
> **username_1**: By all means give a go to see what you get, at best I think you will see moiré patterns depending on the distance and focal length of your camera lens.  
> **username_1**: BTW: I was able to capture real time HDTV at home last weekend but the HDTV was only 1/3 in my field of view, but the trick was to bring the illumination down considerably to match a dark scene and to my surprise there were no moiré patterns. This video is not ready for release yet otherwise I would point you to a link.  
> **username_1**: FYI: Example where it worked, Low light situation where I was able to get my HDTV set to very low illumination with a camera shooting 1080i and rendered to 1080p here: https://vimeo.com/55295820 look at time makers 00:27 and 00:41 in this short video.  

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