Color Bit Depth

Color bit depth is composed of three luminance bit depth channels that accommodate the RGB color components of an image, so that you can see color images. To understand this, let's first look at the single bit depth image.

Bit Depth of an image

A little Bit of information :)

Bit depth denotes the amount of luminance tones that a image can capture by design. The bit is the smallest piece of data a computer has, it is a place holder for a small electrical charge. This place holder can only have one of two possibilities , it has a charge, or it does not have charge, it is like a simple light switch to your room, you have it on, or you have it off.

1 bit : no charge =0
           charge =1

You can make a graphic image made from one bit data units, because it has two possibilities.

Color Bit Depth - 1 Bit Image - dog

Black = 0 (no charge), and white=1(charge).

The 1 bit image to the right is not really a 1-bit image because I have a drop shadow, and gold colored lettering, but the concept here does represent the idea of an 1-bit image, only black or white pixel values.

For a 2 bit image, 2 single bits can be used together to define a small luminance range of values that has four potential different brightness possibilities as a unit. Adding more bits to define potential brightness values is know as Bit Depth

2 bit : no charge = (0,0 = black)      no charge found in either bit.
           charge = (1,0 = dark gray)  a charge found in bit #1, but not bit #2
                    (0,1 = light gray) a charge found in bit #2, but not bit #1
                    (1,1 = white)      a charge found in both bits.
                     

We can mathematically find the number of possible tones that we can make buy dedicating many bits together to describe unique brightness values.

If a "single bit" = 2 possibilities, (on or off)
Then 2 bits used together = 2x2 or 2^2 or = 4 possibilities
4 bits used together = 2x2x2x2 or 2^4 or = 16 potential shades, which includes a black and a white.

color Bit Depth - Bit Depth of an Image

The Color Bit Depth Image

The "Color Bit Depth" image is simply combining three regular luminance bit depth dimensions together to accommodate the Red, Green and Blue color channels of the image, which allows us to see the illusion of color when your monitor displays the color bit depth image buy projecting the RGB components of an image. As described on the link Photography Basics all color images are really three B&W images displayed with RGB filters for the digital image, when displayed together they represent the color image.

Color Bit Depth - 2 Bit Image - dog

The jpeg image uses 8 bits to describe shades of brightness, offering 2 to the power of 8 brightness levels, or 256 different brightness levels for a single luminance option. A color image for a Jpeg will need to use Red, Green and Blue to make many colors. If each of the individual RGB colors can display 265 tones of brightness within their own color channels, then there is a potential for 256R x256G x 256B to make a total of 16,777,216 colors. So each pixel in a Jpeg has this color potential for 16 million different colors in the image.

When starting out in digital photography, this certainly sounds like more than enough colors.

Tiff and RAW files have greater potential for recording different brightness and colors because they have a much larger color bit depths to their file format designs. Your digital camera may have the potential for 2^12, or even 2^14 color per color channel for each single channel of RGB color.

So lets say your camera is using a 2^14 bit depth per channel, your RGB color bit depth would be this value times three. That is a color bit depth of 4,398,046,511,104 unique colors and tones. This certainly sounds like over kill, but really it is not, considering how you can use this in editing to recapture subtle differences in tones that are buried in the bright highlights or dark shadow areas, and making them more distinctive in your final image edit.

Because you have so many more different levels of brightness represented, you have processing options in your RAW file processing software, that allows you to use these levels of brightness for greater image quality, and more elbow room for making adjustments. Basically, by editing, you can spread the luminance range out some with adjustments, or compress them with more flexibility. This moves some of the luminance details from the vary bright end of the scale into a brightness range where you can see differences in brightness easily, where before they may have appeared just as bright light areas of your image, this is an editing function called Recovery. This is where we are able to reclaim details from these areas and seemingly stretch out our dynamic range from just 6 stops of light, to 9 stops of light, you really only get this options from the larger bit depth images.

Color Bit Depth - Dynamic Range

Above is a diagram for Exposure Brightness range or what is commonly refered to Dynamic Range. On inspection you can see that for a Jpg image, the scale labeled "Normal Dynamic Range" is about 6.5 stops of light from pure black to pure white. The Jpeg image can only represent this dynamic range with 256 different levels of brightness per channel of RGB, because it is an 8 bit image.

By design, our histogram on the camera will only display 255 levels of brightness also, even though a Tiff or RAW file is capable of recording more shades within this same dynamic range spread of 6.5 stops, resulting in sixteen thousand levels of brightness. This is not a problem though, because the 14 bit image will look the same as the 8 bit image when you capture it and it is displayed on the Histogram. It is only in processing that you can recover and make use of some this definition of luminance and details found in the larger color bit depth image file.

So to summarize just a bit, The larger the color bit depth of the image, the more room there is for storing more luminance values, and this can be a big help in editing.

Jpeg files are 8 bit images, and they have the space that is large enough to cover about a 6.5 stop dynamic range from the image sensor used by your camera. So for starting out and learning digital photography basics, it will do just fine. During editing, your pictures a little more warm, sharper, brighter just as you can with any other image files but you barely have any room for adjustment without compromising image quality some, particularly if you happen to save and close the file with intent to come back and work on it again later. I will explain about this on the link Jpg Files .

For now, I would recommend that if you want to edit your Jpeg files that you first copy your original image file and save the new file under a different name, and save as a Tiff file format, and then edit only those copied files, never edit the original.

Later as you progress and build confidence with editing then you might want to start saving your images in the camera as a RAW file. You will eventually begin to appreciate the many advantages that they can offer. It still does not hurt to carry over the same practice of duplicating the original, saving under a new name and then editing only the copied file.

RAW files will allow you recover more details in the highlights and the shadows. Don't expect huge differences though, just some more room in the bit depth size of the file to define some more details, it's good exposures that gives you the image you really want to work with. With RAW files, edit choices don't reduce the quality of the image after saving the file. We go into more information about the RAW File Format on it's own link.

Color Bit Depth

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