Gray area with gray cards

[Abitconfused]

Do neutral gray cards reflect all colors evenly or absorb all colors evenly? And is there a difference between these two?

[pnodrog]

Is a glass half empty or half full...

Surfaces/dyes/pigments can exhibit a number of characteristics such as iridescence, fluorescence etc that can influence the apparent reflected colour. However a good grey card should not have any of these special properties and hopefully any visible light that is not absorbed is reflected.

[Mike Buckley]

I love the title of the thread.

[Dave Humphries]

Hi Ed,

The only thing that matters is what they reflect, since we can't see what they absorb (and I can't think, for a grey card, what else could happen to the light). Whatever percentage they don't reflect must be being absorbed.

This will be true at whatever individual frequencies of light hits it, be that: a broad spectrum, a tungsten lamp, or even a laser (the latter emitting only a single frequency).

That said, as Paul says, it is a bit like 'six of one and half a dozen of the other'

[xpatUSA]

I love the title of the thread.

A bit like Doug Kerr's gray cat on an ash-pile

http://dougkerr.net/Pumpkin/articles...e_Metering.pdf
.

[mikesan]

As I understand it, a "neutral" gray card (suitable for white balance) should reflect the full spectrum of the incident light without altering the balance of the various frequencies in that light.

[pnodrog]

A bit like Doug Kerr's gray cat on an ash-pile

http://dougkerr.net/Pumpkin/articles...e_Metering.pdf
.

Thanks for the link. A good article that I have taken a copy of but I don't think I will print it for using in the field...

[rpcrowe]

I use a WhiBal card as my reference. The manufacturer touts this card as extremely neutral...

http://www.whibalhost.com/_Tutorials.../03/index.html

[Manfred M]

First of all, let's remember that gray is any target that has equal values that are not pure black (0,0,0) or pure white (255, 255, 255). So in theory, a gray card could be anything in the range of (1,1,1) through to (254, 254, 254). In practice, something more mid-range is more practical as you don't want to have a shot of a reference card where one or more channels are clipped.

A middle gray card (18% gray) is gives the widest range. There are numerous reputable card suppliers, with the Kodak Gray Card being one of the best known ones. Are all cards spectrally neutral? That is hard to say and I strongly suspect some of the low end ones might not be. Stick with a well known and reputable brand like x-Rite and you should be fine.

[Tronhard]

I had an epiphany watching a tutorial on studio photography...
When we do our next repaint I am going to paint my some walls either white or 18% grey...

[Mike Buckley]

I had an epiphany watching a tutorial on studio photography...
When we do our next repaint I am going to paint my some walls either white or 18% grey...

The floor, ceiling and three walls of my makeshift studio are black. The other wall is white.

[Tronhard]

I suspect 'SHE who must be obeyed' would take issue if I tried that, but I think I can get away with the white and grey!

The floor, ceiling and three walls of my makeshift studio are black. The other wall is white.

[xpatUSA]

I suspect 'SHE who must be obeyed' would take issue if I tried that, but I think I can get away with the white and grey!

How about 90% white and 18% gray to match the Kodak?

Used both sides of one this very day to figure out the ISO of a modified DSLR . . .

[Tronhard]

Ah NOW you're talking!

[Manfred M]

The "pro" studios I shot in had black walls, floors and ceilings. They nicely reduced reflected light.

The room I do my editing in has gray walls - that also works well.

[IzzieK]

I had an epiphany watching a tutorial on studio photography...
When we do our next repaint I am going to paint my some walls either white or 18% grey...

Not a bad idea at all...I wonder what hubby will think if I do that to my den?

[mknittle]

This is interesting because I am going to get a bedroom for a studio when we move. I have been debating on all black, black with one white wall or any other combination. I am leaning toward all black but one white wall would be handy.