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18% Grey Card question


S

Shreck

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New to this. Did not put a subject heading on first submit, so I have
asked question a second time. Dubious start eh.

What is an equivalent RGB color to a standard 18% grey card?
Is there a way to have calculated this RGB color? [confused]

Could you sucessfully Color Pick from a photograph of 18% card?
 
Hello Shreck,

Assuming that a 18% grey card is equivalent to a 18% grey setting used in the swatch palette in Photoshop. I calculated the value for you and came up with a hexidecimal setting of D6D6D6 for 18% grey. You can plug that value into the Color Picker # in Photoshop.
Or as you have already suggested you can load the picture into Photoshop and use the color picker tool to select that 18% grey.

anepu
 
My math skills are substandard, so I just used the grayscale ramp in PScs and dragged the eyedrop across the strip until it read 18%K, then I reverted back to RGB mode and the info palette read:
R:218 B:218 G:218
 
The RGB values set at 218 coincide the 15% grey swatch using Photoshop 7. It appears as best as I can tell that 18% grey would have a RGB value of 214.

anepu
 
I get 209/209/209

which is also logical:

255 corresponds with 100%
so 1% corresponds with a change of 2,55

meaning that 18% corresponds with a change of 45,9

as greys start counting from white downwards, we have to substract this change from 255, which gives 209,1 or 209
 
... and to summarize. :B :rofl:

Just to add to and simplify Erik's thoughts, think of it as the lightness with 100% being the lightest.

Find the values easily using the colour palette.
Choose the Greyscale ramp and set the value required.
Go back into the palette and choose another colour mode, RGB, Lab, whatever.

Instant readout and also set to foreground colour for instant gratification. ;)

Al.
 
Ah! I see what you guys are talking about now using Photoshops greyscale & rgb sliders. Was wondering what nitro was refering to.

Thanks for screen shots! Rantin

Have learned something new once again here.

:)
anepu
 
18% Grey Card

Thanks for the information.
An 18% Grey card is very important in Photography and
yet I had never found any information about how PS
treats it. It's the only known color I have ( I have an 18% card)
that I am sure is an accurate color. I would like to see if my printer
and I are on the same page, so to speak.
 
18% Grey Card

Thanks for the information.
An 18% Grey card is very important in Photography and
yet I had never found any information about how PS
treats it. It's the only known color I have ( I have an 18% card)
that I am sure is an accurate color. I would like to see if my printer
and I are on the same page, so to speak.
 
Shreck - You need to make sure you have calibrated your equipment. Once you have done that, open the picture of/with the gray card on it (make sure you are using a good color profile for the document). You can send a print directly to the printer now and see if it matches your screen. If you want to do any color adjustments, you can use the grey card as a reference. Use the color info dropper (the eye dropper that lets you put multiple reticles on the screen). Click on the gray card and adjust your levels/curves/color until you have 18% gray showing in the info palette. Then send a print and compare with your document and with your original gray card.
 

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