50% grey is 149 149 149.
However, you can simply pick a neutral grey from the Appearance Tab in Screen Properties!
I always thought 50 percent was 128 128 128. not really important, just good to hear of someone who actually knows the importance of using a neutral background to color correct.
can be a value from 128-133 depending on clipping set for shadows and highlights…
Thanks
wrote in message
50% grey is 149 149 149.
However, you can simply pick a neutral grey from the Appearance Tab in Screen Properties!
Michael…
Could you please turn off the "AutoQuote" feature in your newsreader? It makes for a lot of unnecessary text clutter.
If you’d like to quote specific parts of a previous message for clarity and continuity, please do so manually.
Thanks.
Oops, I forgot about that with Adobe forums ..
I always thought 50 percent was 128 128 128
Not as defined by Photoshop’s swatches.
If Adobe lays is spec it’s probably better to sun with it.
They "invented" or "discovered" TIFF (it’s a philosophical point) and there are some very rigorous TIFFs knocking about 🙂
What the HELL does that mean?
Can somebody translate that for me?
Phoz,
You should recognize a strong Scottish accent when you see it typed by now.
In "American" English, deebs meant to say (I think; I am after all only of Scotch heritage): "Aye, Adobe’s fair brilliant! I have no tiff with ’em. And if you disagree, y’re knackered, ye and the horse ye rode in on."
Cheers,
Art
Sooner or later somebody’s going to have to publish a book of collected deebisms.
I hereby claim the exclusive right to be excluded from the list of nominees.
JJ – granted. Dismissed 🙂
as a ps – doncha know that TIFFs are not just conduler level but tends to be a research spec as well?
To contribute something more interesting than translation to the conversation, those of us old enough to remember film have great respect for Kodak’s visual rules and interpretations….
And according to them,
"A light gray might have RGB values of R 18 G 18 B 18 A 50 % gray will have RGB values of R 128 G 128 B 128
A dark gray might have RGB values of R 210 G 210 B 210" Source: <
http://www.nyip.com/tips/digital_dialog1201.php>
And then the traditional 18% (reflectance) grey card would read: 121,121,121 according to some unofficial sources (not Kodak).
Art
Thanks Art – it is good to see some professional wisdon seeping in to the discussion.
Your reflections are appreciated
A dark gray has 210RGB?!!
This has got to be a typo. They just stated that black is 000RGB. How can you have a light gray at 18RGB.
That site isn’t Kodak; it’s the NY Institute of Photography. The context is color-correcting an image using the eyedropper on a Kodak greyscale card included in the image. No reference to what color profile is being used. And they got the light and dark gray reversed. I’m not sure I’d read too much into their figures. And if 50% gray is 128,128,128, there’s no way 18% gray is going to be 121,121,121.
In any event, there is no single direct correspondent between 18% reflectance (which is what the 18% gray standard refers to) and any given RGB value. It depends on the gamma, color profile, rendering intent, and any number of other factors. As one site put it:
The traditional 18% gray card was set to approximate the middle of the human perceptual tone range. If you could do exact tonal reproduction, this card would have RGB values of about 117 in a gamma 2.2 compensated curve (this is a curve that does exact reproduction and is compensated for proper display on a gamma 2.2 monitor. The values would be about 98 for a 1.8 gamma compensated curve).
<
http://www.rmimaging.com/information/dgc_faq.html>
See also: <
http://www.aim-dtp.net/aim/calibration/middle_gray/>
And if 50% gray is 128,128,128, there’s no way 18% gray is going to be 121,121,121.
The 50% and 18% are as different as apples and oranges. The 18% is the amount of light reflected from the gray. The 50% is the computer values used to create a gray.
I’m not saying that the 121 figure is correct, just that you can’t discount it because it is so close to the 128 figures.
Grayscale cards are probably a different thing to RGB settings on a computer yes?
Don and deebs are correct.
A greyscale card is a card that reflects 18% of the light that falls on it, the amount that a camera’s light meter is keyed to. It is not a 82/18 percent mix of white and black or black and white. It is used while shooting to get an accurate light meter reading from a known subject when you’re shooting something where an accurate exposure is a Good Thing to have.
An RGB value for grey on a computer is the amount of red, green, and blue pixels required to produce a given shade of grey. Which is, as Don poins out, why the 121,121,121 figures may very well be correct.
They’re apples and oranges… but if you take a picture of the "apple 18% grey card" you can then, because it’s a known, measurable grey, figure out what RGB values are required to make it look correct on your "orange RGB" monitor. (And as a bonus, the Kodak grey card has no color cast, so you can fine-tune your color mix based on it.)
It’s another type of calibation — if you include a grey card or a macbeth color checker in a photograph, you can more easily calibrate an accurate exposure and color rendering on screen and the printer.
Art
Besides, grey cards have mulitple uses or did have when i first started in laboratory work.
One of these, for example, was to gauge shade shift of dyes under lightfastness or washfastness testing.
The difference between before and after was gauged using grey card comparisions
(but that was a fair while ago)
Digital middle gray depends on the gamma of the color space being used.
You could simulate middle gray by having a pattern with alternating pixels of black al white.
A neutral grey matte board is often used to to surround color and b/w photos, etc. It might be called museum grey or something like that.
My PS 7 and Elements have a similar neutral grey background as their desk top color to function as the defining point of the picture plane. Individual colors will then appear to sit at or recede from, or sit above this plane in varying degrees.
Josef Albers (1888-1976), an educator with Bauhaus roots, investigated color relationships and their apparent depth within the picture space in his painted series "Homage to a Square".
artguy
