Color Theory & Practice a 24 BIT Color Image Is Made From

Home , Digital photography

Color Theory & Practice

http://webexhibits.org/colorart/bh.html

DIGITAL DEFINITIONS

A 24 BIT color image is made from the combination of THREE 8-bit images. A RED image, a GREEN image, and a BLUE image.

8 bits + 8 bits + 8 bits = 24 bits

ADDITIVE COLOR Adjusting color by varying the quantities of each color of RGB light Cyan

Blue Yellow

Red

ADDITIVE COLOR ADDITIVE COLOR Adjusting color by varying the quantities of each color of light Adjusting color by varying the quantities of each color of light

Green Green Cyan

Blue Yellow

Magenta Magenta Red

ADDITIVE COLOR ADDITIVE COLOR Adjusting color by varying the quantities of each color of light Adjusting color by varying the quantities of each color of light In digital photography, you adjust light to change colors. This affects how inks are adjusted in the subsequent print.

Magenta BLUE YELLOW Red RED CYAN Yellow Blue GREEN MAGENTA Green Cyan

SUBTRACTIVE COLOR LIGHT INKS Adjusting color by varying the quantities of each color of ink

THERE ARE SEVERAL DIGITAL COLOR SPACES (or “modes”)

RGB

THERE ARE SEVERAL DIGITAL COLOR MODES CMYK

LAB THERE ARE SEVERAL DIGITAL COLOR MODES:

RGB (Three 8-bit channels=24 bit)= Red, Green, Blue (light) This is a way of manipulating light in a way that’s consistent with how digital cameras see and monitors reproduce the world.

CMYK (Four 8-bit channels32 bit)= Cyan, Magenta, Yellow, and Black (ink) Monitor Printer This is a way of manipulating ink in a way that’s consistent with how printers reproduce the world.

LAB (Three 8-bit channels) = Lightness, A-axis, B-axis This is a way of converting ﬁles between RGB and CMYK - they pass through this mode to best translate the colors. The visual differences between two color modes GRAYSCALE (one 8-bit channel) = Gray (methods of color reproduction) This is a true grayscale image with 256 shades of gray. It is different than the grayscale images we made by using a adjustment layer on an RGB image. This is one of several reasons why your prints will never exactly match the computer screen...

GAMUT = The range of colors a speciﬁc device can reproduce.

chromaticity chart = plots the range of colors that can be perceived by an “average” person, or the range of colors that can be reproduced by a speciﬁc device. Screenshot from the Apple Colorsync utility

So, what does this mean for you?

• Software and hardware typically handle all the conversions that need to be done, so you don’t have to do anything.

• When working with photographs, always use RGB color mode and don’t change out of it unless you’re are explicitly told by someone to do so.

Most importantly, this should help explain why pictures look different when viewed on a screen vs. as printed objects.

Question:

My pictures look pretty good to me - why would I even bother with adjusting color? When considering the observer, color is a sensation Newton’s model accounts for two of the three participants, but not the third (how color is perceived). Affecting the third and is affected by... participant is critical in inﬂuencing someone’s response to an image. your mood your gender your native language your age the time of day and many, many, other factors...

Answer: Answer:

Seeing a photograph with inappropriate color balance is a little like Seeing a photograph with inappropriate color balance is a little like listening to a piece of music that’s slightly off-pitch. listening to a piece of music that’s slightly off-pitch.

Not only will it likely not produce the kind of sensory experience Not only will it likely not produce the kind of sensory experience you want, it may even work against the kind of message you intend to you want, it may even work against the kind of message you intend to communicate. communicate.

uncorrected uncorrected corrected Question: My pictures look pretty good to me - how can I even tell if they need to have their color adjusted? Question: My pictures look pretty good to me - how can I even tell if they need to have their color adjusted?

uncorrected corrected Answer #1: Evaluate parts of your picture that should have neutral values. Use the info palette and make corrections to force those values to become neutral.

Question: Question: My pictures look pretty good to me - how can I even tell if My pictures look pretty good to me - how can I even tell if they need to have their color adjusted? they need to have their color adjusted?

Answer #2: Answer #3: Try an auto correction to see what photoshop tries to do, Experiment and practice. Seeing color and adjusting color study those changes, then go back and make intelligent requires practice. manual adjustments.