A Finer Grasp of Certain Terms

The terms Value, Brightness, Luminosity, Lightness, and Gain.  I see two or more of them in some software.  What exactly are the differences?

And Intensity.  Is it related to saturation, value, or something else?

Thanks for any tips!

• edited September 2017

You cannot really separate a term taking it out of context. So if you ask about Gain, then in exactly what effect are you inquiring about.

That said, Gain is normally used to denote an amplification of some value. Amplified by what formula is not defined.

Luminosity and Lightness basically refer to your image without consideration of the color component. So think black and white. The brightest spots are close to white and the darkest are close to black. As for the diff between the two it is mathematical. Luminosity takes a different percentage of each color component (RGB) to "create" the black and white version. These percentages are roughly equivalent to human visual perception. Lightness is really just an average of the min and max range in the image.

Brightness is really just what it sounds like. Increasing it raises the overall brightness of the image. Exactly what formula/curve that is used for the brightness change is not defined. Typically it is a curve with the end points pinned (black and white) and the in between points are are adjusted along a simple curve. Kinda like you would use in the curves effect.

Intensity could mean anything. It really, really depends on the context. The same could be said for value.

• Moderator

For the most part, most of these terms are interchangeable most of the time.

We'll treat "Intensity" as our generic base definition. Intensity can be treated as "how much" from minimum to maximum.

"Value" is generic, since a value is any number assigned to any parameter of any function in the software. I.e. Opacity, position, glow intensity, etc all have a numeric value.

In color theory there are additive and subtractive. Subtractive is paint and print, and we don't need it for this discussion. Additive is lighting and CG/VFX.

Additive starts with black and adds Red, Green and Blue (illuminating) channels to create colors. Adding Red and Green makes Yellow. Adding Red and Blue makes Violet, adding Green and Blue makes Cyan. Add everything for white. That, more or less, is the RGB color model.

Now... There are several mathematical models to define color (RGB, YUV, Lab, and HSL--also HSV, HSB and HSI). For your question we want Hue, Saturation, Lightness/Brightness/Value/Intensity.

Hue is the base "color." Red, Yellow, etc...

Saturation is "how colorful" the color is. Zero saturation is pure gray value. 100% saturation is maximum "colorful."

Intensity, Value, Brightness and Luminance all have the same meaning. How "bright" is the color on a black/white scale. Zero is black, 100% is white.

Lightness is similar to Luminance/Brightness/Value/Intensity, except, instead of using the pure numeric value, the software modifies the values to match the way the human eye responds to brightness.

Gain is a semi-generic term. A gain value is a modifier added to a base value. In general you'll more likely see gain on audio gear. But think of a gain as adding or subtracting from what is already there. Increasing audio gain raises volume levels. Broadcast video cameras have gain--which electronically boosts the sensor. Gain on a video camera is similar to ISO on a DSLR or mirrorless camera. Raising ISO also electronically boosts the sensor.

Make sense?

• Thanks so much!

I've noticed graphic design tends to use value and saturation, while some video colorists talk of luma and chroma instead.

Zoner Photo Studio was the app that got me wondering.  It has tools and filters with settings that use all the above terms.  So just as incandescence, phosphorescence, luminescence and fluorescence all mean different things,  I wanted to know how these are used differently.

Have a great weekend  !

• Moderator

"I've noticed graphic design tends to use value and saturation, while some video colorists talk of luma and chroma instead."

Value and Saturation are more common with graphic design because of printing considerations. If you're doing artwork for print then you're probably working in a CMYK (Cyan, Magenta, Yellow blacK) color space for pigment primaries. Video on the other hand, deals with RGB light primaries. While the terms are used interchangeably, the math behind them in the computer models is different because of the differences between pigment and light primaries.