Value related terminology and other questions

[PieterV]

Hi guys, I'dd like to apologize in advance cause I'm pretty tired and my brain's not really working properly. Spelling is probably falling appart too... But I was pondering about certain terminology regarding value, and color in relation to value...

One of my questions is, what exactly is midtone? This might seem academic but it's confusing me for a while now. Is is the value you get in places where the form shadow and form light overlap, as in 'transition' between the light and the dark, the shadow edges? But I have also seen it defined as 'the darkest light in the light'.
I take it this kind of depend if you're working with mainly 4 or 5 values.
Where you would have 5 values, midtone would be in the middle of your value-range. So... form light =[highlight, light] transition=[midtone] form shadow= [shadow, core shadow].
And if you would have 4 values... form light =[light, midtone] form shadow [shadow, core shadow].
So according to wether you're using an even or uneven number of values the definition of midtone would change?

Another question, does 'highlight' mean the same as 'lightest light', or is it just the short from for 'specular highlight', as bieng the spot that directly reflects the lightsource trough the surface normal.

How do you know the 'local value'? How much light would you need to accurately know the local value. How should we define the local value when painting from life? I always struggle with this. Or would one just look for the right midtone and expand from that?

I'm also wondering what the difference between the terms value, tone, luminosity, brightness and lightness are.

I know that brightness is the brightness of a pixel within the RGB spectrum, but does not take into account saturation or chroma, which causes a value shift on it's own. And lightness, as used within lab color space does take into account the effects of saturation.

So I guess value, luminosity and tone essentially mean the same as lightness?
Am I mixing up luminosity with 'luminance'?

Loomis writes in his books that cast shadows are the darkest shadows. Why?
I guess that they are darkest under certain light conditions, but considering shadow is simply absence of light I don't see why they would be darker then form or core shadow.

I guess that from a practical point of view, knowing the difference between these terms wouldn't help me that much, but I want to know the correct way, I think it's a bit like the discussion about what the "true" primaries are.

[dpaint]

When you are talking about value remember value is relative to the things around it. While the value scale is fixed, a scene can be keyed so that only uses part of the total range. Midtone or halftone usually refers to the local value of an object not the middle value of the overall scene. So if you were to block in your image using midtones the midtone for a face would be different than a midtone for the boot. How you divide your image depends on how you want to mass your objects together, since you only have about forty values (ten step value scale in quarter increments) total to work from and nature is showing you 100 times that.

Value and tone are interchangeable terms. Luminosity and lightness are also the same. Brightness is a function of color saturation or chroma. The rule of thumb is -to brighten something increase its saturation- to lighten something increase its value.

Indoors cast shadows will tend to be darkest shadow especially near the base of the object and lighten as they move away from the object. Core shadows tend to be lighter because they can be affected by the ambient light and reflected light in a scene if there is any.

[riceface]

When you are talking about value remember value is relative to the things around it. While the value scale is fixed, a scene can be keyed so that only uses part of the total range. Midtone or halftone usually refers to the local value of an object not the middle value of the overall scene. So if you were to block in your image using midtones the midtone for a face would be different than a midtone for the boot. How you divide your image depends on how you want to mass your objects together, since you only have about forty values (ten step value scale in quarter increments) total to work from and nature is showing you 100 times that.

Value and tone are interchangeable terms. Luminosity and lightness are also the same. Brightness is a function of color saturation or chroma. The rule of thumb is -to brighten something increase its saturation- to lighten something increase its value.

Indoors cast shadows will tend to be darkest shadow especially near the base of the object and lighten as they move away from the object. Core shadows tend to be lighter because they can be affected by the ambient light and reflected light in a scene if there is any.

hmm that makes alot of sense to me, i alwyas thought midtone is 50% or half way in the greyscale..

so u block out shapes the same way u block out with color, using the midetone of that particular space and then u figure out the shadows and light of that midtone..

[PieterV]

Okay, I tought about it some more and I think I have arrived at something that makes sense (I hope!)

http://img200.imageshack.us/img200/1985/valrangeterms2.jpg
excuse the crappiness it's almost 4am and I should be sleeping. It's not really accurate either... :X

The tonal scale is the maximum possible value range. It is usually devided into 9, 10 or 11 intervals.

The valuerange is the maximum range of values that can be present on a certain object or on the scene. It is context specific.

The therms lights, lightest lights, midtone, darks and darkest darks stand for the orientation of a value within the valuerange. Lightest lights would be 100-80% of the maximum possible brightness within the specific tonal range. lights would be 80-60%, midtones 60-40%, darks 40-20%, and darkest darks 20-0% possible brightness within the specific tonal range.

Form light and form shadow is basically the seperation into two major tones of the light on an object. The rule is that the lightest shadow in the form shadow is darker then the darkest light in the form light.

Core shadow is the darkest shade within the form shadow

The highlight is the lightest value within the valuerange. It is caused because of surface specularity and directly reflects the lightsource. It changes location depending on orientation in relation to the object.

Reflect light is light that bounces of near surfaces onto the object. It is not the lightsource itself. Also known as indirect light, radiosity, bounce light.

Ambient light is a form of indirect light.

The transition or midtones are the values that lay inbetween the lightest and darkest tones.

Cast shadow is an area with less light because the light is bieng blocked of by another object. I don't know if it should be darker...

Hmmm does this sound right?

Anyway, gnighty... :D

[riceface]

is the object specific value range the range of the ball to the right of it? and is the reflect light hiting the ground or is the ground light hitting the ball?

[dpaint]

Look at it like this- on this color card I have black, blue, red, yellow and white
Half the card is in sunlight and half in shadow. It shows you how color and value are relative depending on lighting conditions. Even at the extreme end of the range of the scale black and white are affected by light and shadow. If they are then every value between them is too.

[Pencilcandy]

Loomis writes in his books that cast shadows are the darkest shadows. Why?

The darkest darks would be in places where 2 objects meet.

[briggsy@ashtons]

dpaint, hope this is seen as helpful and not pedantic, but that grey strip in your shadow area is jumping out. Since it's similar in tone to the red and blue strips in the light, it should logically be similar in tone to the same strips in the shadow. I've adjusted it and some of the others slightly to keep the brightness ratio consistent at 40% for each colour. Because the change in brightness is proportional, a dense black would change in tone much less in absolute terms than a bright white.

Great work on the explanations!

[PieterV]

Look at it like this- on this color card I have black, blue, red, yellow and white
Half the card is in sunlight and half in shadow. It shows you how color and value are relative depending on lighting conditions. Even at the extreme end of the range of the scale black and white are affected by light and shadow. If they are then every value between them is too.

It's not that I don't understand value range. It is the terminology that goes with it which sometimes confuses me. My question is more etymological / paradigmatic.

I was wondering if dark, darkest darks, light, lightest lights and midtones meant the same as the terms core shadow and highlights etc... and if these were related to the tonal scale or to the object-specific value range... so the 'midtone' value on one object could be the shadow value of another object. But 'shadow' is a relative term that has no correlation with the picture as a whole, 'shadows' would have that but it could still mean different values. 'Midtone' could mean both a middle gray (so relating to the tonal scale) as well as the value that lies inbetween the brightest light value and the darkest shadow value on an object.
I guess they are related but do not mean the same thing per se.
(as darks, lights etc would relate to a certain part of the value range, and the other names aren't values in themselves but the personalities/type of shadow).
For example if you could have really strong bounce light from the left while on the right there would be a very dim light source and the specular highlight would be actually more subtle then the form light caused by the reflected light. I don't think I ever saw this in reality but it would just mean that these terms are just shadow types and not value-identities.

What I wrote in my last post seems to make sense to me, because most terms are context / object specific except for the numerical values themselves.

I think allot of people throw these terms around interchangeably, or do not stress what they .actually. mean. Which I think is what confused me in the first place.

[Elwell]

I think allot of people throw these terms around interchangeably, or do not stress what they .actually. mean. Which I think is what confused me in the first place.

Exactly. The definitions are fuzzy or overlapping, and the term one person uses for something may mean something else when somebody else uses it. It's more important to know all the different meanings, and try to figure out specifics from the context. Partially this is a result of English having such a large vocabulary, with many words that or are either synonyms or that have very subtle shadings of difference, partially it's because many people writing about art don't really know what they're talking about, or at least have more trouble expressing themselves verbally than visually.