Friday, July 28, 2017

Relative color temperature on skin tones

Mathieu asks:
I have been struggling over the last months trying to understand how to handle the green parts (cool notes) of the flesh in a portrait.

In the Fundamentals of Painting by Mogilevtsev I could not understand the following text: "The light consists of three parts: the highlight and halftone are cold, and the light space between them is warm." I thought only the shadows are warm and all the parts of the light will always be cold. So what does he calls "the light space" between them? 

Gurney—On page 22, Mr. Mogilevtsev implies that the "light space" is the area between the highlight and the halftone (the halftone is the area just before the light side turns to shadow). What he calls the "light space" might also be called the "lights" or just "the light side." 

Within that light side there can be subtle variations in color temperature. 

He is indeed painting the halftones cool, specifically greenish. The halftones are an important area to observe closely for their value, for the abruptness or softness of the edge as it turns to shadow, and for their relative color temperature. 

He makes the point that relative warm and cool tones can give life to a portrait and I would agree with that. His states that the rules he's talking about refer to painting a portrait indoors. Traditionally an indoor portrait would be lit by a relatively cool north-facing skylight. In that case, the lights are generally cool compared to the shadow, because of the coolness of that blue skylight relative to the bounced light of a wood floor or warm-colored rugs, etc.

Charles Hawthorne
However, I would be skeptical of any fixed rules about cool/warm relationships, such as saying "outdoors in sunlight the light is always warm and the shadows are always cool." If there is very warm light reflected back into the shadows, or a secondary light that is very warm, the shadows can be warmer than the light side. 

Or the color of light in the shadow can vary according to the direction the planes are facing, such as a person standing at the beach, with blue sky above, warm sand below to one side, and blue water below in another direction. It all depends.

On the portrait of the woman, I don't understand the logic behind the green parts of the flesh colors. Where to put those greens? Are they at the edges of the planes right before they turn? 

Gurney—Yes, he seems to be placing the greens at the turning of the form. This is something that old masters often did. It may or may not look convincing, depending on how it is handled. Sometimes this cool effect in halftones is the result of the way you glaze color over a grisaille or "dead color" underpainting.

Let's step back for a minute to remember that the appearance of any flesh tone color, whether in light or shadow, is a combination of: 
1) the color of the surface (local color)
2) the color of the light 
3) plus additional factors as subsurface scattering. 

So, warm local color plus warm light equals a very warm color note. 

I try to consider first the local color as it varies across the form. The color across the mask of the face can vary a lot, as any makeup or prosthetic specialist will attest. It's often redder in the cheeks and nose, darker around the eyes, lighter and yellower on the forehead, and bluer or greener in the neck or chin, plus there are effects caused by makeup and sunburn. 

The reflectivity of the skin varies too, and that factor can influence your color and value choices.

Then I consider the sum total of the colors of light shining on each plane. It might help to place a white plaster head near the model in the same light in order to study those influences.

The color you mix for any given plane will be a combination of all those factors. 

Mathieu continues: When speaking about "cool" or "cold" colors in the light areas why do I always feel that the yellowish and reddish color of these parts is warm? On the above portrait by Rubens the light areas doesn't seem "cold" to me.

Gurney—You're right that most skin tones are on the "warm" or orange side of the spectrum, but we're speaking of a relative thing here.

Sometimes it can be hard to judge relative light color when looking at a living model. That's why painting from a white plaster cast can be helpful for understanding both form and light. By removing the effect of local color, you can see what's going on with the relative temperature of the light.

Bottom line: be skeptical of fixed rules, be guided by your observation, and always compare, compare.
Previous Post: Color Zones of the Face


artsworth said...

That is a brilliant answer and typical of this blog. A big thank you James,for taking the time out to pass on your knowledge. Regards,Will

broker12 said...

When I run into an obvious green, I often use terra verte mixed with my flesh tone. It is a weak color, and therefore, easy to manipulate. Sometimes, I'll use a dab of viridian mixed in with my flesh tones, but viridian can quickly overwhelm the mixture. In some instances, plain old yellow ocher and ivory black or raw umber will do. I often see subtle green shades, and for some reason it is too easy to get their value too high and they end up looking too bright next to the other flesh tones. This is an informative and educational post. Thanks.

James Gurney said...

Thanks, Broker and Artsworth. Good tip about the terra verte. I like that using in landscape, too.

Don Rogers said...

In Chris Legapi's videos, he explains that it is a 'law of color' that when you change value you should/must change temperature. Therefore in the halftone, we must understand it's temperature and value too; then, when we mix to the next lighter value, it should change value and temperature simultaneously. Adding white to a color will basically make it appear lighter in value and cooler in temperature due to the white pigment. Will that value change also qualify as a temperature change? I too, remain in that area of confusion but we must keep practicing and working on it all. Thanks for the tip to work from a white cast to identify the color of your lights, halftones and shadows.

Don Ketchek said...

While books can certainly be helpful, always beware when anyone spouts "rules." What James Gurney wrote is far better advice than found in most books - and, alas, too short a text to fill a book or even a page:

"Bottom line: be skeptical of fixed rules, be guided by your observation, and always compare, compare."

Color is relative to what other colors are near and adjacent. So comparing is a must. And in some cases, the "rules" have become simplified and distorted over time. Whereas today, many artists quote the rule: "warm light, cool shadows" and "cool light, warm shadows" - it is far better (when using this guideline or rule) to think: warm light, COOLER shadows, and, cool light, WARMER shadows. In other words, with warm light, the shadows need not be a cool color, they are just COOLER than the color in the light, and that color may still be considered warm in comparison to other colors.

Anon Nimus said...

I think of it this way. The light most facing part of the form will be the highest value and chroma of the local color, and as the form gradually turns away from the light towards the shadow terminator it loses both value and chroma. I mostly use raw umber to lower the value and chroma of skin tones. Low chroma colors or near neutrals can appear cooler or warmer depending on the surrounding higher chroma colors due to simultaneous contrast. Highlights are not part of the form but reflection on the form of the light source, which can either be warm (sunlight, incandescent light, candle) or cool (northlight, overcast light). Reflected lights in the shadows can also be warm or cool depending on the secondary light source or color of the object reflecting on the shadow side, and same principle as in the light side, they lose value and chroma as the form turns away from the reflected light towards the shadow terminator.

Mathieu N. said...

Hello James, I just discovered this article now, thank you very much for having developed the answers to my question point by point through examples. I see things more clearly now.

All the best,


Eve said...

Hello James this is an amazing blog and I've learnt so much. What I was trying to find originally, and can never seem to discover, is a picture with the distinct temperature zones actually marked on it. I am never sure what I am looking at and I ask myself, is this the halftone? is this cool or warm? which part is which? I am still learning. Could you post such a map of a couple of faces, such as the Rubens and another, just so I can have it literally pointed out to me? I would love this!

Best regards,

illykay said...

Yes, I've been thinking a lot about this too. My current feeling is that it's worth looking into, but at the same time as you mentioned, it's important not to get stuck in recipes. Those cool halftones can make the form pop, but, yes they're difficult to handle for sure.
I wanted to understand some of the traditional techniques so I thought the best place to start was using tempera, because you don't have to wait for it to dry in the same way as oils. I read Daniel Thompsons book on tempera painting and he gave a basic method or concept that has affected my thinking (for better or for worse), that has to do with a darker tone laid over a lighter tone gives a quality of transparency+(relative warmth), a lighter tone over a darker tone gives semi transparency and appears cooler. This pearly quality he calls opalescence. He also mentions that a tone of matching value laid over the first will appear opaque. I'm sorry I'm going to run through this pretty quickly - please feel free to check that book out if you haven't already. So the reason that this excited me was that I was having trouble painting water at the time. I was trying to get the right relationship between transparency and opacity, but it just came out like stained glass with correction fluid. So Daniel Thompson says that this semi transparent cooler tone created by laying light over dark is the intermediate between opacity and transparency. That made a lot of sense to me. He suggested laying down this cooler semi transparent tone down first and working outwards from it. Transparently into the shadows and opaquely into the lights. That made sense to me, but also more generally the order of how the paint is applied. i.e dark over light or light over dark. I had an intuitive feeling of this before (when you paint a lighter tone over a darker and the chroma just gets sucked out and it's beyond you to repair it!) but this helped to clarify this, or at least set me on the right road.

illykay said...

So.... looking at tempera technique.. because tempera is so transparent it's impossible not to consider these concepts really. That's what I found at least. My first impression is that it's in working around the limitations of tempera that you are forced to come up with ingenious methods that the older painters seem to have employed and these were probably translated into oil painting. (Most notably in tempera it's difficult to lay down a flat tone and to cover underlying paint.) If anyone is new to the medium and wants to get an idea then check out the channel: Painting the Light on Youtube. He comes from an icon painting background. Often he will paint an overall tone for the face and then paint the light on the face into that. This first skin tone layer (or first light as it is sometimes eferred to in icon painting) struggles to cover the underlying tone first laid down and inevitably you have an intermediate band of opalescent, cooler, semi transparent smoky paint between the shadow area and the light area. It's difficult to avoid. That's a cool midtone. Now, wikipedia mentions different renaissance painting styles coined by Marcia B.Hall. notably sfumato and unione. Sfumato sounds a lot like what I have described with the smoke like opalescent quality in the mid tones. Unione is described as: 'Unione is similar to sfumato, but is more useful for the edges of chiaroscuro, where vibrant colors are involved.' That must be a way of creating the midtone from laying darker tones over lighter tones musn't it? Does anyone have any thoughts about that? It could be achieved by running glazes over the cool halftones, or by working the other way round from light into dark like watercolour. I apologise if I'm confusing anyone with way too much information here. Its better to keep these things simple, but..... as I say it's something that has been on my mind a lot and any discussion would be helpful.

illykay said...

And in relation to the instructions in the Russian book... I love it and also the drawing book by him too, but it doesn't really give too many explanations, just a couple of recipes, notably laying in those silvery green midtones first. Using those green midtones would be a matter of taste as discussed already, but what I found interesting was that his midtones were transparent (like a glaze or an imprimatura) He then.. and this is what I'm struggling with.. laid in the light areas next to them and I'm not sure if he repainted those cooler halftones at this point. This gave a beautiful warm quality to the lighted area of the face, but I found it incredibly difficult to paint over that initial lay in of the light area, because of the drop in chroma when you kill the transparency there. This might have been accentuated massively because I was trying to do a copy in tempera, but I could see the same problem coming up in oil. I reason that he would have had to have painted more impasto and with brighter paint.. using more cadmiums in the skin colours to maintain the brightness in a second layer. It bothered me because of this and also when he repainted the cool halftones in the second layer.. they were necessarily more opaque than they would have been using a more subtle system. Haha which really gets to a bigger point.. the crossover between older painting and more modern painting. Impressionist painters seemed to embrace opacity in the halftones and shadows to some degree, where 'older' painters were generally allergic to it. They went out of their way to preserve an ordered relationship of opacity/transparency. The advantage of the new painting style is that it offers new possibilities in placing vibrating colour tones next to each other. 'Impressionist' or just more contemporary in feel like Moglievtsev's example in the book. Both systems have strengths and weaknesses. It interests me to what degree they can be combined or to what degree you have to elect to employ one or the other mode. And probably getting back to the initial question more than the tangent I have created :), how we reconcile these 'classical' picture making devices with what could be called 'realism' (what works in picture making vs. what we see.) It's obviously personal, but also so nice that we share a tradition we can mine and talk about. The point of Moglievtsev putting in the cool halftones is to create vibration I think. warm shadows, cool halftones, warm skin tone, cool highlights. Or I would say more accurately in the creation of wide intervals. Same as in music. Chords sound bright and harmonious when the tones don't sit too close together. It's how they are seated around the colour wheel that is important. Clashes might appear when tones are sat face to face or possibly cramping anothers style when too close. (Two people all over each other that detract from the whole - something like that.) So yes, creating contrast and interest through bigger shifts in colour across the portrait. It might work better when the picture doesn't have strong tonal contrasts.. I've noticed that. Moglievtsevs painting does not have strong chiaroscuro.

Eve said...

Thank you illykay, I am studying everything you said! I appreciate your reply. Eveline

illykay said...

And another thing which is I think is interesting is that analyzing pictures on the computer I very rarely find blue/green or even grey halftones. I was just looking at the Death of Adonis by Rubens and what you would have sworn blind were blue halftones are just more neutral versions of the colours in the lights. Rubens seems to exemplify that cool/warm system.. (at least it appears obvious in his figures) and I could well imagine that he could have achieved those halftones without using blue or even black, simply by thinner scumbles of skin colour over a slightly darker underpainting and then laying on the lights with more colour and thickness in the next layer.