What are the differences between Brightness and Lightness?

[mizi]

Thanks.

[Ed A. Ortiz]

I think brightness has more contrast.

[Gernot Hoffmann]

Luminance is measurable. Lightness is perceived Luminance.
Brightness is perceived Lightness relative to some average
level in an image or environment (yes "in contrast to..").
A more accurate definition is in R.W.G.Hunt, Measuring Color,
but probably not interesting for anybody here.

In PhS HSV = Hue-Saturation-Value the word "value" means the
lightness,brightness,luminance.
HSV is the same as HSB, where "B" stands for brightness.
In HLS "L" stands for lightness.

In non-scientific speaking all these words can be used for the
same purpose: make an image more or less light.

Hope this helps and please don´t blame me for the academic
hairsplitting on the one hand and the ill-defined nomenclature on
the other ...

Best regards --Gernot

[LenHewitt]

Gernot,

>>the academic hairsplitting on the one hand and the ill-defined
nomenclature on the other <<

Chuckle!

[Lawrence Hudetz]

Light has always been a thorn in my side so far as definitions are concerned. I believe the reason is that, besides having hard, scientific definitions, we are also concerned with the subjective evaluations and reconciling what we see with these measurments. Light-ness is more subjective than brightness, but what does it mean? Light vs. dark, but also, light vs. heavy.

The perception of color is entirely unanticipated by the objective measurements of that phenomena.

It's interesting that as soon as we depart the visible spectrum, descriptors and measurements become more manageable.

So, academic hairsplitting is the norm, it seems, when it comes to light.

Try metamerism for another hairsplitting (and hair raising!) subject.

[Phosphor]

Who was it (a France native, I believe) on these forums that provided us with some delightfully fake-latin nomeclature for hair-splitting...something like follicular quadrifurcation?

Man, I wish I remembered the exact phrase, it was hilarious. Stoopid me, I forgot to paste it into my collection of word goodies.

[Lawrence Hudetz]

Yeah, stoopid you! :)

[dave milbut]

So... what's the difference between Brightnes (as in the Hue Saturation (Lightness) dialog) and Brightness (as in Brightness/Contrast dialog)? Anything? (Anything in English?)

[Lawrence Hudetz]

Run both. They behave differently.

What else I might say should be said in some other language.

Escapes the censors heavy hand!

[dave milbut]

I think Ed had it right in post 1. Either that or Lightness has less contrast. :)

Brightness seems to work on a narrower range of light than Lightness slider does. You can turn up brightness and still retain some contrast even at a pretty high value. With Lightness the overall picture contrast degrades quickly.

Larry, I do use both regularly, just asking from a curiosity standpoint. (And maybe to help the original poster get a fuller answer to his question, with all respect to Gernot, I have no idea what you said man! <g>) As is said about most art, I know what LOOKS good, but that doesn't tell me why or what it's doing. Either way, I won't lose sleep over it. Nite nite! :)

[Lawrence Hudetz]

As the Duke said: (paraphrasing here) "If it looks good, it is good!"

I rarely use the Lightness slider, and then no more than 10 points, if that much. If I need more, I go back to Levels or Curves.

I finally did use the Brighness/Contrast tool, (once) and when I needed it, no other tool would work. It behaves exactly like darkroom paper does. It's a much maligned tool, and I hope Adobe doesn't drop it.

[George Austin]

Since this IS a PhotoShop forum, I would say it is appropriate to define the parameters questioned in accordance with their usage in PhotoShop. The PS meanings may or may not be valid in other applications. With that understanding, Brightness and Lightness in PS can be described as follows:

Brightness: The highest of the color values in the three channels (R,G,B) expressed as a percentage from 0 to 100. Thus 255 is brightness 100, 0 is brightness 0, 128 is brightness 50, etc. The values of the less bright channels are NOT considered. Only the maximum value matters.

Lightness: The only place this seems to appear in PS is in the Hue/Saturation dialog box, where it is the label on one of the sliders. The slider has a range from -100 to +100. That allows you to change the values in all three channels at one time (Master slider) by the Lightmess setting.

The Lightness setting here is the percentage change to be invoked. With percentages, you must always ask "Percent of what?" And here it is the percent of the difference between 255 and the current channel value for positive increments, or between 0 and the current value for decrements.

When the top slider is on "Master" the Lightness percentage change is applied to ALL 3 channels. That seems to be why the term "Lightness" has been introduced in PS, because you cannot use "Brightness" which, as stated above, applies only to one channel (the one having the highest color value).

As for "luminosity" and "luminance", that's a longer story and it is late. Suffice it to say they ARE DIFFERENT, and they are precise, quantitative, calculable parameters.

George

[Gernot Hoffmann]

George,

a clean and clear approach.

It cannot be excluded, that "Lightness" is meant here and
there in PhS in the sense of Lab Lightness.

A good occasion to correct my previous statement:
Luminance is measurable. Brightness is perceived Luminance.
Lightness is perceived Brightness relative to some average
level in an image or environment.

A more accurate definition is in R.W.G.Hunt, Measuring Color,

but this lacks also understandability (not my fault).

Best regards --Gernot

[Lawrence Hudetz]

I agree reluctantly with George, that we confine ourselves to the PS meaning.

Reluctant because if we are to be able to communicte effectively, then the definition has to be the universal definition, if one exists. Lacking that, or choosing a different definition for a parameter, we must communicate that up front. Otherwise, we run the risk of talking past each other.

In Gernot's restatement, we have the perception of a perception, something that is totally lost in any objective approch to defining parameters. Perception has to do with the brain's response to stimulii, while Luminance, Brighness, or Intensity, if you will, can be quantified as the number of photons impacting a site in a given time. Exposure is propotional to Intensity x time is a formula I remember from sensitometry.

Wasn't it light that eluded scientific truth in the late 19th Century, giving rise to Quantum Theory? Looks like light still possesses that elusive quality!

[Gernot Hoffmann]

Lawrence,

I agree too that we confine ourselves in this thread to the PhS
meaning - if this should be somewhere defined, but it isn愒.

HLS Lightness, HSB=HSV Brightness/Value, CieLab Lightness are
something totally different. All the three are well defined, but
PhS is here by no means clear.

R.W.G.Hunt is one of the best color experts (Measuring Colour,
The Reproduction of Colour).
He has defined the meanings of the three words "Luminance",
"Brightness","Lightness". Scientists use the words like this, and
it愀 ugly, that the meanings are pre-occupied by HLS,HSB=HSV
and CieLab and additionally by common speaking.
You are right - Lightness is the "perception of the perception",
not only perception, but additionally RELATIVE to some area in
an image.

If you read my first post again, then you will see, that the scienti-
fic definition was merely the introduction.
The rest was or is: apply image processing by appearance, then
the accurate meaning of B and L is not relevant.

It愀 highly relevant for the creation of color charts, by the way.

Best regards --Gernot

[Lawrence Hudetz]

I'm going to Powells Technical bookstore and look for that book.

Thanks

Lawrence

[Turk32]

Then explain the difference between a Lite Brite and a bright light.

And how come only a person or pet is Bright, and sodas and beers are light?

How come you can't bright a match, but you can brighten a day?

You can lighten a load, but you can't brighten the same load.

Why is the opposite of Heavy, Light and not Bright?

Answer these questions, and the real definition will come through...

I also thought that Lightness worked primarily through the color scale, increasing the RGB value, whereas Brightness affected the color's placement on the grayscale range (similar to levels), which is why it was paired w/ contrast to increase the clarification between the colors on the white end of the spectrum and the colors on the black end. I'm not a Color expert, by any means, but did think that this was the fundamental difference. One worked the RGB scale, and the other worked the 'grayscale'.

Now that might shed some light on the subject, but how come it doesn't shed some bright on the subject?

Why didn't God say let there be Bright, and why doesn't Cheer make colors Lighter?

...man this is confusing...

[dave milbut]

George, brilliant.... that I can understand! :) We should stick to PS definitions only since that was the original question.

Brightness: The highest of the color values in the three channels (R,G,B)

... Only the maximum value matters.

Lightness: ... allows you to change the values in all three channels at

one time (Master slider) by the Lightmess setting.

That's about how I observed it. The fact the the brightness only works on the max value is the key to understanding it. Thanks.

[dave milbut]

Why didn't God say let there be Bright,

he did. it was mis-translated to light. :)

[Michael Morgan]

Actually God said, "Light Be" and light was.
I got into the light defining thing a long time ago and a photographer told me to look it up in the dictionary. Supposedly, it is one of, or the most defined word in the dictionary. I looked it up in a small dictionary and found 63 different definitions, even some including insects landing on something.

[Hans-Georg Wilden]

I think the french phrase, Phosphor is referring to in his contibution th this thread (No.5) is "Enculer les mouches". And this whole thing sounds like this would be a good characterization.
Honny soit.... Hans-Georg

[George Austin]

Hans-Georg

"...this whole thing sounds like this would be a good characterization"

Bien contraire, mon ami. Understanding the parameters we use day-in and day-out is vital. The differences between lightness, brightness, luminosity, luminance, etc are real, quantitative, and definable and have very practical consequences which you seem to be demeaning.

George (with an "e" on the end!)

[hasan.s...@gmail.com]

On Monday, March 24, 2003 at 5:37:53 PM UTC+1, mizi wrote:
> Thanks.

I have tried to explain the difference between lightness and brightness in the following video

https://youtu.be/tq2y2BseUaE