What are Chroma Key and Green screen?
Chroma key or green screen is a color-based background replacement. After shooting, the live video footage can be replaced with different backgrounds of your choice.
How do we achieve it?
To achieve this effect we shoot on a chroma key backdrop which is usually bright green in color. Later when editing, either by removing the green color from the shots or replacing it with an image, the chroma key becomes visible to us.
Why Blue Screen then? Why not Red or other colors?
The reason behind using a blue screen is that when using any other color like red or green, due to light absorption, the subject tends to lose its original brightness. The blue absorbs least amount of light and hence provides a better chroma key effect.
How do we achieve it?
The process of chroma keying is quite complex and requires precision, but can be achieved with practice. You need to identify the areas that should be made transparent or ‘key out’ as it’s commonly known as. This is done using professional video editing software such as Adobe after Effects or Apple Final Cut Pro. For those who don’t have access to expensive software’s there are lots of other applications available for this purpose like Corel Video studio, iMovie etc which can help you accomplish your goals.
What tools do we need?
We firstly require a Blue/Green screen background: It is important to choose a blue/green screen that is evenly illuminated because if the light on it varies, shadows are created which are difficult to key out.
The backdrop should be large enough so that the subject being filmed fills up most of the frame. It also needs to be portable so you can easily carry it around or keep it in your car for location shooting.
There are many options available when it comes to portable backdrops, one can choose based on their needs and budget but I would recommend a company called C-stands by Matthews Studio Equipment as they offer quality products at affordable prices. One portable backdrop that has received good reviews from many people is The Chroma Key Backdrop Set by MSE.
What about lighting?
Chroma key requires consistent even lighting otherwise shadows and gradients can be created which can make it difficult to chroma key.
To the left is a list of portable lighting options I recommend:
The Intova LED Par Light offers good results with little setup. The light has 4 color filtered lenses which help in creating an even screen across the backdrop and also allow for filters to be easily attached for creative effects or corrections in post-production. It’s portable and offers power options like AC Adapter, Battery Pack, Solar Panel, D-Tap. Some users have faced problems with this light when used indoors but when used outdoors it works fine.
The Chroma Universe Portable Mini backdrop lights are portable, energy efficient and easy to use. They offer great lighting options with power options like Battery pack, AC Adapter and a video light option with a dimming knob for various levels of brightness through a remote. You can also get a shotgun microphone which is compatible with most portable lighting systems by the company. One downside of these lights is that they do not have color filters but you can make do without them if your subject contrast ratio isn’t very high i.e. if the chroma keyed shot has several colors in it then using colored gels can cause problems in post-production or when compositing background images with the footage from chroma keyed shots. However doing this is an advanced technique which requires experience and time to perfect.
Another portable light for chroma key is the Chroma-Q Color Force II LED Light. It offers RGBW color changing capabilities meaning the light can be set to any number of colors using its dimmer controller. It can also playback several color combinations using automated programs or sound activated mode, additionally it comes with a microphone input so you can use it as a portable mini PA system too! The downside of this portable light is cost but if budget isn’t problematic for you I would recommend getting one of these lights because they provide excellent results. One important thing to remember when buying portable backdrops and portable lights is that some come with stands included while others don’t so make sure what all comes in the package before you buy. You can however easily get portable light stands or portable backdrop stands from Matthews Studio Equipment and other similar companies.
Conclusion:
A portable blue/green chroma key backdrop with portable lights is a necessity if you want to take your chroma keying seriously. They are portable, easy to use and an investment that will save you time and effort in post-production.
