Values when dealing with different saturations & lightness

[Senira]

One question I've always had about values is how to deal with objects whose base colors differ in saturation and/or lightness from one another while all objects are sharing the same light source.

This has become a particular issue for me because I've been trying to follow E.M. Gist's advice about using only five values for light and dark. It's been a great help to me in all situations but this!

I'm sure I'm not applying the theory right, so here's an example of what I usually do when confronted with this situation:

Here there are three balls, each of them a different lightness, and all being lit from the upper right light. What I do is give each ball the same relative level of shadow-- each ball's darkest shadow is at 15% brightness, and blends up from there.

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Now, common sense says that if you have three balls of different lightness, they shouldn't be equally dark. However, if I make balls two and three lighter than ball one in their shadows, they no longer have enough contrast. It's the lack of contrast that makes me think example one is the correct approach to this situation, but I could be entirely wrong.

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The same problem arises when I try it in color, and this gets trickier, because then saturation comes into play. I know the rule of thumb is things in light =Brighter, more saturated and things in darkness= darker, less saturated. But if I start with a ball that's, say, 25% saturation(ball 1) , vs one that's 80%(ball 3), I end up with a 25% ball that looks like grey muck in the shadows. Do object with less saturation maintain the same general amount of saturation in the shadows? Better yet, what is the lower limit on how less saturated a shadow should be vs. the base color of the object?

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Any help on this subject would be much appreciated. These are questions that have had me scratching my head for a while.

P.S. I'm terrible at shading balls. I know. :nohope:

[Opilione]

In my experience the shadowed values for the differently hued objects are not the same. The shadow of a high-chroma orange is going to be lighter than the shadow, equally distant from a light source, on a high-chroma red. Also the values you're displaying here aren't for light, they're for colour, so the issue of saturation wouldn't really be an issue, unless the object itself is of a very low chroma.

What it actually looks like what you've got there is three balls all the same colour or at colours with the same value/chroma, with different kinds of light-reflective surfaces, because all their shadows are the same, it's just the way they're reflecting the light source that's different. For example, the one in the back could be silicone, the second could be plastic, and the front one would be glass.

Then when it comes to the final picture you're adding a lighter value, not reducing the digital saturation of the colour (or the chroma), which should make the colour more grey, not pink, unless you're working in a multiplied layer which would mix the pink with the greys underneath.

[briggsy@ashtons]

1. Brightnesses work proportionately: e.g if surface A reflects twice as much light as surface B in the shadow, it should reflect twice as much light as surface B in the lights. Ball 1 is 57/16 = 3.56 times as bright in the lights as in the shadow, so try applying this ratio to the other two. This would make the shadow brightness around 84/3.56 = 24 for ball 2 and 93/3.56 = 26 for ball 3. Your shadows for balls 2 and 3 are too dark in your first picture (16) and too bright in your second (35).

2. You need to understand the difference between saturation and chroma.
http://www.huevaluechroma.com/012.php
Since you seem to be working with a white light, the chroma will increase from the shadow to the light but the saturation (S) should be about the same.

[Senira]

Thanks guys! I followed your link, briggsy@ashtons, and I did some reading about chroma vs. saturation on the net. Let's see if I'm understanding this correctly.

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(I switched to cubes, since I am incapable of rendering spherical objects. Opilione, I assure you that their appearance as different materials was entirely unintentional. )

So, cubes 1-3 are examples of objects with differing chromas under the same light source. They reflect the same relative amount of light, but the higher chromas of #1 and #3 give them brighter shadow areas than #2. Also, because the light is white, and there are no other surrounding colors to influence the cubes, the saturation of the shadows remains constant.

Cubes #4 and #5 are examples of cubes with the same saturation who, once again, have differing shadows because #5 has a higher chroma.

#6 is a cube that's reflecting light from cube #5. The saturation drops on the left side because the pinkish cube is introducing more grey to the blue cube.

Have I got it right?

[Opilione]

Looks good to me!

[briggsy@ashtons]

Quick learner! It makes a big difference to know what you're doing, doesn't it. Everything looks about right apart from the left side of cube #6, which looks too desaturated considering the surface bouncing the light is only slightly red. You could get the effect of a subtle added light by taking that colour and overlaying it at very low opacity in screen or linear dodge mode over the colour you would otherwise have used (i.e. with S = 82).

[Senira]

Thanks guys! You were a great help. :)