[Prometheus-ANJ]

Hey.

I've been working on a tutorial for quite some time now. I'm not sure if I'm progressing cuz I discover more stuff everyday.
Anyhow, here's some illustrations that are supposed to go with the tutorial text. I'm hoping the illustrations are self explainatory though.
What more related light effect could I do illustrations for? I'm I explaining/illustrating something the wrong way? I exaggerated the colors a bit on some of the illos. I didn't wanna use photos cuz of copyright issues, although I could probably snap some myself.



Plz excuse my bad handwriting. The PS5.5 text tool sux so I stay away from it.


...oh, I guess I could post this too. It's a quick photo ref study I did some year ago or so, and decided to use as a tut illo.

Values and proportions are okay on this one, but it suffers from bad stroke economy and brush size (tried to fake it best I could). There's lots of random strokes dancing around and not really describing anything. Don't fill large spaces with a scribbly small brush (unless your doing the hatching thing), that will make the surfaces look wobbly/bumpy like a fat woman's ass. I use a brush that is about 2/3rd of the detail I'm rendering. Since I use the paintbrush in PS5.5 a lot I can pressure-vary the brushsize to fit the detail I'm doing.


I haven't really done much on this one. By keeping it clean and simple, and by 'flattening' undescriptive random brushstrokes, the image can get much better with little effort. Don't be afraid of some sharp edges. Spend a bit of extra time on faces.



I should probably so something about values too... how to resist getting too excited with shading/highlighting details.
Anyhow, it would be cool to make some sort of collaborative effort on a giant art tutorial or something.
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Yak!

[Lunatique]

AWESOME man. This is the kind of tutorial that's extremely helpful to the ones who are beyond the fundamentals, but not quite experienced enough to know these. Bravo!

[Al Ian]

Man, that tutorial is awesome! Its the kind of stuff I am just starting to get into. I want MORE!!!!!!!!!

Oh, and I about bust a lung laughing when I read the comment about the celulite enhanced rear end!
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http://jmarkey77.home.bresnan.net/

[Tomasis]

just awesome.. I understand better about saturation and reflection

Is it always so when highligts and shadows have low saturation and midtones - 20%-30% more saturation? Or do it exist exceptions for this theory? Sometimes "true" color of different substance confusing me because it doesnt show its true color when it is reflecting with warm or cool color.

How do you play with opacity settings? It is nice to know how everybody works with opacity,

[Gort]

Good work! Yay!


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- Tom Carter

"You can't stop the waves but you can learn to surf" - Jack Kornfield

[Max]

Well done, that's helpful indeed

[AndyT]

Amazing. I'm a big fan of all your tutorials.
Can't wait for the finished text.

I don't get the first image (about exposure) though.
(I just mention this because you wrote you want them to be self explainatory)
What is right ... what is wrong there?
[edit]I just read what gekitsu wrote at Conceptart.org. Now it makes sense.[/edit]

I especially like the "saturation in the middle" point you mention.
Great how you illustrate these things!

Thanks for sharing!
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http://www.conceptworld.org

[bearsclover]

Wonderful stuff!
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Madness takes its toll - please have exact change.

[merlyns]

dammit thats like really good and helpfull

*saves to hdd*

-david
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[Ian Jones]

Can anyone explain the saturation one? Why is the saturation meant to be greatest at the edge of a form shadow? I can see that it looks better, but I'm unsure about the reasoning behind it.

[Lunatique]

[Ian Jones]

hmm... yeah Luna I'm kind of confused now. I'm referring to the warm/cool section. It has a pointer to the middle of the value range and says 'keep / pop saturation in the middle' or something like that.

[AndyT]

I think I see it in photographs.
There is one area where it is close to the local color.

In other areas it's as if you add white (warmer) or black (colder) paint.
(Or if you dodge and burn)

Both take away from the saturation.
It's not necessarily overexposed or underexposed but more or less exposed than the most saturated area.
That is how I understood the illustration and it is how I understood what Lunatique meant.

I might be wrong though.
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http://www.conceptworld.org

[Prometheus-ANJ]

Keep or add saturation between the light and shadow. If you just mix the black shadow and white light you'll end up with a dull grey gradiation and the object loses it's color 'identity'.

Since the shadow often is polluted by ambient light and is darker (more black) it will appear less saturated. Bright colors can't be very saturated cuz there's so much white mixed into them. With better eyes, that could see bigger differences in brightness, we might be able to see saturation in the really bright colors aswell.

Mixing shadow and light carelessly (getting those dirty gradiations) is one of the most common mistakes I see people do.
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Yak!

[zaar]

This is really great! I don't think I've ever seen these ideas and principles illustrated and explained so clearly (and at the same time) before.

My only stupid little complaint would be your use of the word radiosity. I'm no english professor but as far as I know radiosity isn't really used outside of the 3d rendering field. Wouldn't bounced/indirect/diffuse-light be better and make sense to more people?
Most of us understand what you mean by it tough, so I guess there isn't anything wrong with it. Most of what I know about how light work I have picked up while browsing 3d rendering newsgroups and forums, where people pick apart and discuss every little light phenomena there is. I suspect that you have done the same?

[Frost]

Hey, cool stuff Prom. you plan on finishing those with more examples and bigger? Did you end up keeping a copy of that thread on Eatpoo or CA on sub surf scat? Good stuff!

[Ian Jones]

Hey thanks for the clarification guys... that really makes sense now.

[not-epad]

As long as we're talking about radiosity and such, I could use a few pointers with this quick little practice sketch i've been doing...



...hope i'm not being too much trouble.

[jfrancis]

WHITE light lighting SKIN gives you a situation equal to WHITE times SKIN. Put white in one layer of PS and skin-color in another layer and multiply them. You'll get your original skin-color back.

White light BOUNCING off skin becomes, itself, skin-colored. So now you have a situation where skin-colored LIGHT is lighting skin. That's like taking Photoshop and putting skin in one layer, and more skin in another layer, and multiplying those. The result is skin squared, a/k/a skin to the .5 gamma (since gamma is 1/exponent which is 1/2 which is .5) a/k/a more saturated (albeit less luminous) skin.

pale BLUE light lighting skin? Same process...

your tutorial rocks, btw

[Prometheus-ANJ]

I'm writing these things to learn, because I have to formulate stuff into consistant 'rules'. Please feel free to add any thoughts you have.


Here's an odd example of how light reflection work, or how I think it works:

Light reflection works just like... tennisballs bouncing of ...rocky asteroids... how they bounce away depends on the incoming angle, surface angle and how bumpy the surface is (I'm ignoring subsurface scattering and refraction). If the surface is smooth the 'bounce-away' angles will be very easy to predict. If the surface is very bumpy, the tennisballs will scatter away in all sorts of directions.

The intensity of the light depends on the number of tennisballs that enter our eye.

You get a specular on a gloss sphere because the tennisballs can only bounce into your eye if the surface angle is correct, and since a sphere is curved there's only one point where the angle is correct. Even if the surface angle is almost correct you won't see any light from there.

On a more bumpy sphere, chances are that a few tennisballs hit some bumps a bit away from the specular point and thus manages to get the right angle to enter your eye. A bumpy sphere will have a less pronounced speculars because of the bumps randomizing the bounce of the tennisballs, in return, we'll get too see parts of the object we wouldn't get to see otherwise.

That's why gloss object often have flat values and a few specular highlights popping out, whilst a dull (bumpy) object doesn't have any speculars, but appears more volumated cuz more light from the more obscure angles manages to find its way to our eyes. But the main shapes of the object is still important cuz the bumps can't change the bounce angle too much. Don't forget that here on earth we have lots of ambient light bouncing around too, cuz we have so many objects here the light can bounce off. The effects of light are probably easiest to observe in a dark room with a single spot lightsource.

But even something dull like cotton cloth have speculars. I stretched my sleeve out with 2 fingers (marked by dots) and took two pics from different angles.





Here you have the color from the monitor, which appears to be cold white, and the color of the sleeve which is dark brown-ish, then you colorpick the sleeve color, drag up the blue slider a bit, and the green and red just a tiny bit.

If the light from the monitor is strong, then drag up the sliders more. A lightsource will never darken what it 'hits', which might happen if you just mix colors with opacity. In the case with this sleeve and monitor, I would probably be lazy and paint the sleeve dark, then mix a bright cold color into it with opacity and colorpick a color that feels right from that. That only works cuz the sleeve is dark though, and thus I don't risk to make it darker.


You can set the colorpicker to 5x5 average, colorpick the lit sleeve, set the airbrush to difference, paint on the unlit sleeve, and thus you get the difference color, which is 44,43,65 in RGB (varies a lot, but it's basically a dark cold grey). Then you can colorpick, undo the stroke, and set the brush to screen and paint over the dark sleve, and you'll get pretty much the same light on it as on the lit one.



When modifying colors, I use the RGB sliders or I colorpick from my own paintings (alt key in PS). If I want to make a spot more yellow for example I can just colorpick and pull up R and G and paint over with the new color. That or I quickly make a yellow color with the RGB sliders and paint over the spot with opacity.

Mostly though, I pick colors from different spots on the canvas and use the paintbrush on opacity (60-70%) and dab/colorpick multiple times until I get the color I'm after. I almost use my painting as a mix palette. Sometimes I get 'happy accidents' from that.
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Yak!

[jfrancis]

As far as your description of matte vs shiny -- it's pretty good. But don't forget this effect: Even a dull matte surface can become shiny at shallow angles. Look along the hull of the Titanic in this image I found

http://www.paramount-abilene.org/marquee/titanic.html

See how it picks up a bounce into the background color as you look toward the rear of the ship and the angle becomes shallow?

Try it at home. Pick up a dull piece of paper and look along it. See how shiny it gets? The light bounces off the paper like rocks skipping across water

[jfrancis]

If you want to mix colors without darkening, try the screening blend mode.
http://www.digitalartform.com/screen.htm