Monday, June 15, 2009

Octopus violence

I mentioned optical violets in the last post. Several of you raised your hands and asked me to explain optical violets. Above is a Monet that has optical violets all over it, in the shadowed parts of the steam and also effecting all of the dark shadows in the locomotives and the man in the foreground.

In this Sargent, The oyster gatherers of Concale, notice the shadows at their feet, particularly those of the old woman on the far right. Your monitor may display these as more or less violet, I hope that you can see it.. And below is another example;

This is a Theodore Robinson, the distance is filled with optical violets. And lastly;

Here is another Robinson, look for the optical violets in the distance and in the shadows on her skirt. The purple cast on the rock abutment to her left is also caused by optical violets.

Okay, so what causes it? I have heard two explanations, both may be true, However in thinking about how to use violets in my shadows, I prefer the latter of the two I am about to present. The first and most common explanation is that the shadow is influenced by the color of the sky reflecting into it. In a snowscape this is certainly true, and in a seascape also, both are particularly reflective surfaces.

The explanation that I prefer is this though. The light outside is warm. You have heard me speak in previous posts about the shadow being based on the compliment of the color of the light. Bright sunlight has a warm yellow cast. The compliment of that is violet. Therefore the shadow is rooted in violet. I don't know which explanation a physicist would like best, but the second is more instructive to me as a painter.

I make optical violets in several ways. The simplest is a mixture of ultramarine and alizirin (permanent ) however I also pack cobalt violet for "stepping on" shadows. Watch out for reds that contain orange, they mix with ultramarine to make a dirty brown color rather than a violet. I often sketch in a thinned out optical violet color when I am working outside on a bright day. Here's why. When you are drawing you are generally delineating the darks. The shadows are the darks, and violet is a good color to have at the base of your shadows. You wouldn't want to use a bright yellow of course because then you would have a terrible time getting the shadow note. If you are laying your darks in with violet you are halfway to the right color.

Often all that is required after that, is to look at the shadow again, and inject the local color of the object where you see it, in that shadow. Often there is also a sneaky third color that Robert Douglas Hunter used to call the "odd note of nature". That's what you see after you have the obvious color down and you take a second more penetrating look. Then you become aware of another unexpected color. Noting that, often gives a life and believability to the painting. Its something you would never think to make up in the studio. Things like that are why painting ouside gives results that are better than in the studio.


Above is a painting done before the impressionists discovered optical violets. Paintings before their discovery had a sort of brown gravy throughout their shadows.The first reaction of critics and other artists to the impressionists was that they were purple. Incidentally, just because shadows actually contain violets outside does not necessarily mean you have to paint them that way. Learn to do it for sure, but after that there still is a decision making process. You may choose to paint your shadows brown or gray or whatever. The choice is yours. it doesn't have to be right it just has to look good. God made nature, we are making a painting.

If you want to get convincing sunlight in your paintings, try emphasizing the optical violets. There are a number of elements that need to be in place to get light in your paintings (there's another series of posts ) however it is one important one.


Bob Carter said...

As I scientist, I lean toward your second explanation for the color of shadows, although the first may play a part. From the standpoint of physics, what we’re talking about is actually a purple. Violet, in the context of the visible spectrum, is the color associated with the highest frequency of light before entering the invisible ultraviolet region. (Remember ROYGBIV, where R is red and V is violet.) Purple light is a mixture of frequencies from both the red and blue ends of the spectrum. In other words, it’s what you get when you take out the middle of the visible spectrum. When a mixture of red and blue paint gives purple, the pigments are actually absorbing most of the middle part of the spectrum. (Incidentally, as far as I know, there is no pigment that produces a true violet, which would absorb all but the most extreme blue end of the visible spectrum.) All the visible frequencies are present in daylight, but the middle yellow frequencies (the ones we as artists call warm) are present in highest intensity. The blocking object that produces a shadow absorbs all this light. The light in the shadow is always reflected light, which has a different (flatter) intensity profile. Relative to the intense yellow-rich daylight outside the shadows, it looks like the complement, purple. Similarly, if you spend time in a dark room lit only by green light, when you look out to a normally lit space things will look a bit reddish for a time. We seem to crave the compliment. For example, when the surrounding light area is very cool, shadows often appear warm.
As you point out, the clean purple that conveys the optical violet of shadows is alizarin (bluish red) with ultramarine (reddish blue), because neither pigment reintroduces the yellow absent in the shadows. Of course, a mixture with a warm red (e.g., cadmium red, a yellowish red) does just this, and with all three primaries the purple is brownish (not a useless mixture in other applications). The optical violet of aerial perspective (e.g., the distance in the Robinson pieces) needs to be heavier on the blue because the molecules in the air are more effective at absorbing more of the red end of the spectrum, as well as the middle yellow, which drops out pretty quickly with distance. (Was it Carlson who said yellow is on the tip of your nose?)
This may fall into the category of too much information, but this is what you’re likely to get if you poke a scientist. :-)

Knitting Out Loud said...

Loved this post! The minute it stops raining, I'm going outside to check out the shadows. But I thought the change in the Impressionists' palette had to do with advances in paint manufacture. The Barbizon guys painted outside, what color are their shadows? Lastly, did you really write that at 4am????

Stapleton Kearns said...

Thats a great explanation, and simple enough to follow.


Stapleton Kearns said...

I don't know much about science,but I know what I like.

Stapleton Kearns said...

The Barbizon guys mostly had a fine brown gravy in their shadows.The changes in the impressionist palette owe something to the color theories of Chevreul as well.

No, I set it to post at that time, as I know I have people up and reading it that early.

Jeremy Elder said...

I am guessing that you would only see optical violets on warm, sun-lit days then? On a cooly lit, overcast day, it seems like warm shadow colors would be most appropriate.

Stapleton Kearns said...


Why on earth would you need to know about a gray day? What? is there a forest fire out there in Cali ?
Actually, On gray days the optical violet tends to disappear and be replaced by a silvery hue, however shadows get very faint.

Knitting Out Loud said...

Needed a break from knitting, googled Chevreul. Wow! Margerine, 102, French Revolution and Eiffel Tower. Amazing photo of him on Wikipedia. There's a look in 19th century eyes, in 19th century faces, that doesn't exist anymore.

Deb said...

Thanks, Stape. (rhymes with "Cape", where I'm headed tomorrow to drop off some paintings) This was a great illustration ( and great explanation, Bob!) of shadow colors and why. I feel smarter now. And clever title, Stape. You thought we didn't notice, didn't you?
I'm going to end all my posts with the "word verification" word - these would be great making up your own definitions.
This one is "wipen".
v. an oil painting correctional technique.

Stapleton Kearns said...

Wipen, German expressionist method of mind erasure, same latin root a vapid and vermin. Singularly repugnant

Stapleton Kearns said...

I am sure you were pleased to discover the textile link looming there. If you knit ,check out