I think this is one for Lori (funcolors). My guess is no, but Lori will know the answer.

Lori, I knew you wouldn't let us down.

Can the same line of thinking be applied to mirrors, whose main job is to reflect? I have a large mirror in my living room over the couch, located so that it can catch, reflect and try to replicate the daylight from outside. In truth, it does reflect an image of the outside and that is very pleasant indeed, but I do not believe it actually clones and repeats the light that enters from outside. IOW, it's a nice look, but I don't think my living room is literally brighter because of it.

Mirrors are specular which means the smoothness of the glass and silver backing do reflect a quantity of light. How much light and if it's enough to contribute to illuminating the space depend on the mirror and the context.

Thanks, Lori, for educating us yet again.

Now this may be more subjective, but does sheen level affect color perception at all? What's driving this minutia is, I'm thinking about painting my bedroom BM Natural Cream, which looks fine in daylight, but can turn muddy in shadow or on a dreary day. Well, at least the flat paint wall samples do. I was thinking if I used an eggshell or satin finish, that might retain the color but add some depth or sheen or something so the walls don't look so flat & dingy. I've looked at other colors, but Natural Cream looks to be the right ethereal shade with the right amount of body that works with my stuff. I just wonder if at times I'll feel like I'm sleeping inside a giant dust bunny.

Linelle, I have a smallish dining room that years ago I wallpapered with a lovely oriental toile of various taupes & beiges, akin to grisaille. Boy, did that ever go flat in the dining room. No light, no life. Dull, duller, dullest. I fiddled & fiddled with the lighting over the years but couldn't make that room come to life. I eventually put in a huge window unit, 8'x5 1/2'. That did wonders for the room during the day, of course. But the surprise was the huge window bounced around the lights from the chandelier & sconces so the room practically glows at night. It used to be nobody went into the dining room unless they had to. Now evening guests like to linger at the table because it's so cozy.

So maybe with mirrors, it's like my window: go big or go home.

Now this may be more subjective, but does sheen level affect color perception at all?

Yes. Almost everyone will agree that sheen changes color appearance and will perceive that change as darker.

An old painter's trick is to put a piece of shiny Scotch or packing tape over a paint chip if you want to get an idea what it will look like in a gloss finish. (It's actually a cool little experiment to do with a black paint chip.)

BM Natural Cream, which looks fine in daylight, but can turn muddy in shadow or on a dreary day. Well, at least the flat paint wall samples do. I was thinking if I used an eggshell or satin finish, that might retain the color but add some depth or sheen or something so the walls don't look so flat & dingy.

You can distil how you see color down to two parts. Part 1 the wavelengths a color reflects, called spectral reflection. Part 2 the beams of light that shine onto the color from inherent and artificial light sources, called spectral distribution.

Spectral reflection and spectral distribution are the two parts that work together so you can see a paint color. (basically)

The color doesn't change at a DNA kind of level, it just looks like it does. Becuase it has to respond to the quality of light with whatever wavelengths it has built in.

The light, however, does change. A lot. All the time. Like you noted from daylight to shadow or dreary day.

The dreary day quality of light has a limited amount of wavelengths to shine on the color - the reason it's perceived as dreary. Which means the paint color doesn't have much in terms of wavelengths to respond to, so it does what it can but in the dreary light it looks muddy, flat and dingy.

Compared to the daylight quantity of light that has a much fuller spectrum of light to offer which means the paint color can respond with everything (or almost everything) it's got built in - it literally can show its true colors.

That's why sheen isn't going to help. Making the color shinier isn't going to change its DNA. Just like your wearing lip gloss doesn't change your DNA. You're still awm03, just with shiny lips.

So, if the inherent quality of light doesn't have a consistent full spectrum of light for the color to work with, you make the color full spectrum -- and don't use any black to suck up any light because we need as much as we can get.

Still with me?

You change the color's DNA so it has a full spectrum of wavelengths with which to respond to whatever quantity and quality of inherent light there is.

That's why full spectrum paint colors are a thing.

That's why I always say this:

If you have your heart set on BM Natural Cream, call Ellen Kennon and see if she's mixed it full spectrum. She's mixed a lot of BenM colors full spectrum. If she hasn't, you can have her mix a full spectrum version of Natural Cream.

When the light changes, the full spectrum version of Natural Cream is going to appear to change just like the regular version. Except they way it changes, the way it responds to the light will be different. Because it's full spectrum and has no black colorant, it is unlikely it will shift and look muddy, flat, or dingy.

Yes, I understand completely what you're saying about a full spectrum in the paint itself. My two favorite rooms in my house are painted in milk paint: one room is pumpkin, & the other room is a pale hint of blue gray green that I mixed myself. The colors have a life to them that I've never gotten from "canned paint." They look good no matter what the light source or season. The colors do shift with changing light (the pumpkin room turns tomato soup red or coppery brown at times) but they're always pretty, never dull. It's due to the pigments & materials that make up the milk paint, I'm sure.

Well, thanks Lori. Your info has helped a lot. Maybe I'll wander over to the milk paint site & see if I can get inspired by a color. Or maybe I'll just use commercial paint & live with the flaws. Plenty of time to think this through.

Lori blows me away every time with her knowledge. Thanks for the education, Lori!