03-13-2015, 11:32 PM
Technically speaking gurney's rule is really referring to simultaneous contrast, meaning that the perceived value is 100% affected by the values surrounding it, same thing with colour.
Halfway to black is actually true in sunlight conditions, but not all the time. It depends a lot on circumstance obviously, where you are in relationship to the light and how reflective the surfaces are.
Simulataneous contrast is not a rule you plan values out with, it's a phenomenon that describes how colour and value are shifted in our brain. It's hard to replicate it the way gurney did in an actual painting intentionally. Usually, what you end up doing is taking a dark value thats in the lit side and placing it in the shadow side so it appears as a lighter value or taking a value that appears relatively light in the shadow side and putting in the light side so it appears dark. Theres no real rule to it.. its completely and unabashedly situational, and you need to experiment with it to really understand it in an actual painting.
On the other hand, halfway to black was conceived solely as a rule of thumb. It's also situational, but much less so. It's meant as a starting point, and technically speaking it is correct but it might not give you the desired look, so feel free to push and pull within reason to get what you want. Even if you set your painting up so its under perfect conditions for it, ie its 12 pm in the middle of summer and the surfaces are 100% matte, it still might look meh. I find that the rule actually makes more sense in colour, oddly enough. For instance a local value 1 surface should have 4.5 or 5 as a shadow side yet it looks washed out, however when you see that in real world in a colour painting it looks fine.
I can give examples of what I'm talking about if you're interested or if that didn't make sense
Halfway to black is actually true in sunlight conditions, but not all the time. It depends a lot on circumstance obviously, where you are in relationship to the light and how reflective the surfaces are.
Simulataneous contrast is not a rule you plan values out with, it's a phenomenon that describes how colour and value are shifted in our brain. It's hard to replicate it the way gurney did in an actual painting intentionally. Usually, what you end up doing is taking a dark value thats in the lit side and placing it in the shadow side so it appears as a lighter value or taking a value that appears relatively light in the shadow side and putting in the light side so it appears dark. Theres no real rule to it.. its completely and unabashedly situational, and you need to experiment with it to really understand it in an actual painting.
On the other hand, halfway to black was conceived solely as a rule of thumb. It's also situational, but much less so. It's meant as a starting point, and technically speaking it is correct but it might not give you the desired look, so feel free to push and pull within reason to get what you want. Even if you set your painting up so its under perfect conditions for it, ie its 12 pm in the middle of summer and the surfaces are 100% matte, it still might look meh. I find that the rule actually makes more sense in colour, oddly enough. For instance a local value 1 surface should have 4.5 or 5 as a shadow side yet it looks washed out, however when you see that in real world in a colour painting it looks fine.
I can give examples of what I'm talking about if you're interested or if that didn't make sense