Is red and blue brighter than green and blue?

Answer 1

The same intensity of red light, green light and blue light would have the same "brightness" as measured by a light measuring device (known as a photometer).

But, there are two complicating factors - firstly the fact that light doesn't come from a perfectly pure source, but instead from a lightbulb or from the sun; and secondly that we don't have a perfect system for measuring light, but instead the human eye-brain system.

Lets look at both of these separately:

-Sources of light:

Light usually comes from sunlight or from artificial light such as a lightbulb. These have a maximum intensity (maxiumum brightness) in the yellow range, which means that they usually produce brighter reds and greens than blues. But this depends on a number of factors. Noon day sun near the equator is usually much brighter, and also much more yellow. Further north, more red and green light gets dispersed, and so light appears both less intense and also more blue. Near the north or south pole blue will be much more intense than at the equator.

-Your eye-brain system.

You have sensors in your eyes that are sesnitive to colours known as "cones". They are called S, M and L cones. S are sensitive to violet, blue and green colours (and are often called blue cones), M cones are sensitive to a range of colours from greeny blue through to orange (and are often called green cones), and L cones are sensitive to a range of colours from greeny blue through to deep red (and are often called red cones).

There are far far more M and L cones (which are mainly sensitive to red and green light) than there are S cones (which are sensitive to blue light). In fact less than 5% of your cones detect blue light.

Your brain tries to compensate for this by making the blue appear just as intense in your "minds eye". However, be aware this is a sort of "brain trick" to compensate for the lack of blue detectors. For this reason, your eyes can see red objects much more clearly than other colours.

As to your question "Is red and blue brighter than green and blue?"

It doesn't have a clear answer. If you mean, is the total intensity of light measured by a scientific light measuring device (a photometer) when you add red and blue light greater than that of adding blue and green light then the answer would be no, the brightness would be the same.

But the terms "red", "blue" and "green" are subjective anyway, and defined relative to human experience.

So if you mean would a person have a subjective experience of seeing red and blue more brightly then green and blue, then sure that's certainly a possibility, particularly given the ambiguities in your question. For example, if you were to paint red, yellow, green and blue lines onto a piece of paper and look at it under natural daylight conditions, you could well see the yellow as brighter as the sun given off a peak intensity in the yellow region of the spectrum.

So overall I would say the answer is "it depends what you mean, but in general terms, no they are equally bright"

Answer 2

It depends on the specific shades of red, blue, and green being compared. Generally, bright red and blue hues can appear more vibrant than green and blue when they are of the same intensity level. However, brightness can also be influenced by factors such as luminance, saturation, and context.