Blackmagic Forum

Hi, what do people mean by the term Key? I've heard it used in the context of pulling a fast key to work more quickly or as a key output or key function.
Can someone take me through the delineations here?

Cheers!

There are several definitions for "key" in this industry.

Key Light
Keyframe
Chromakey

Might be worth Searching for a web site listing "film terms".

A key is usually a method of creating transparency using the image's specific pixels value. It's mostly either a chroma key or luma key. A chroma key would be either RGB, HSL, YUV, etc. Luma key would always be based on the luminance value.

Now, a key is different than a mask or a matte, even if they all are used to create transparency. Surely there is more info available on the web.

Annaël Beauchemin wrote:Now, a key is different than a mask or a matte, even if they all are used to create transparency. Surely there is more info available on the web.

I think that the results of a key is a matte that can be used as a mask, though?

One set of words describes a process, other the result. Often they are used interchangeably and it really makes little difference.

Mask is the same as matte is the same as result of keying - a key. Masking sometimes means matting with rotoscoping but can also mean using one element to mask another, and it doesn’t have to originate from roto. For example using a texture to mask other footage. Key usually implies the process of keying: creating a matte with some automatic method.

Matte originates from “(traveling) matte”, which means hand-painted holdout used in multi-exposure photography.

Key, as in “chroma key” originates from a trade name of a photochemical process that allowed creating mattes from analog film.

Annaël Beauchemin wrote:A key is usually a method of creating transparency using the image's specific pixels value. It's mostly either a chroma key or luma key. A chroma key would be either RGB, HSL, YUV, etc. Luma key would always be based on the luminance value.

Now, a key is different than a mask or a matte, even if they all are used to create transparency. Surely there is more info available on the web.

You would have thought so, but I couldn't find anything satisfactory. This thread has been more useful.

Annaël Beauchemin wrote:A key is usually a method of creating transparency using the image's specific pixels value. It's mostly either a chroma key or luma key. A chroma key would be either RGB, HSL, YUV, etc. Luma key would always be based on the luminance value.

Now, a key is different than a mask or a matte, even if they all are used to create transparency. Surely there is more info available on the web.

Thank you!

Hendrik Proosa wrote:One set of words describes a process, other the result. Often they are used interchangeably and it really makes little difference.

Mask is the same as matte is the same as result of keying - a key. Masking sometimes means matting with rotoscoping but can also mean using one element to mask another, and it doesn’t have to originate from roto. For example using a texture to mask other footage. Key usually implies the process of keying: creating a matte with some automatic method.

Matte originates from “(traveling) matte”, which means hand-painted holdout used in multi-exposure photography.

Key, as in “chroma key” originates from a trade name of a photochemical process that allowed creating mattes from analog film.

Cheers thank you. I've seen a few youtube videos with titles like 'tips to pull a fast key', which was so vague, I took it as just fast grading. And i was advised to select a key function and set a key output to zero to deactivate a power window at a certain point in a timeline, so the usage of the word can be a little confusing.