if u're interested in video production checkout what is Chroma Key?

chroma key

Most of us often ask ourselves , In these movies , do actors need physically to be on the place in order to shoot a video?

the answer is NO!

If want to know why read what is is chroma keying

Chroma keying, is a special effects / post-production used heavily in many fields to remove a background from the subject of a photo or video - particularly the newscasting, motion picture and videogame industries. A color range in the top layer is made transparent, revealing another image behind. The chroma keying technique is commonly used in video production and post-production.- 

Watchout this video for more 

to do chroma key u can use the following softwares:
1. Adobe after effects (any version)
2. Sony vegas
etc...
if u need any of the mentioned software, other post production or u want to know more in production softwares just contact us or comment 
references: www.wikipedia.org/chromakeying
www.youtube.com/whatischromakey