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5 – Digital Terms

Most students can ignore this section until later.

Pixels, Bits, & Bit Depth

Pixels

The term pixel is from picture element.

When photons are collected by the millions of photosites on your camera's sensor, pixels are created.

These pixels are the small squares that make up your photographs.

Most people can skip the next section about bits and bit depth.

Bits & Bit Depth

Each pixel is made up of data called bits.

A pixel in a JPEG file has 8 bits of data for each of the three colors, red, green, and blue.

Color Bits
Red 8
Green 8
Blue 8

Each of those bits has two possibilities—it can be either on or off.

With 8 bits, and with each bit being either on or off, there are 256 combinations for each color of the three colors, red, green, blue.

Take the number of positions, 2, to the power of the number of bits, 8, to get 256 possible combinations (28).

Color Bits Each Bit Total Possible Combinations
Red 8 bits On or Off 256
Green 8 bits On or Off 256
Blue 8 bits On or Off 256

Now, if we combine the three colors, there are many more combinations of each bit and its two possibilities of being on or off.

Take the number of possible combinations for each color channel, 256, and multiply them together.

256 x 256 x 256 = 16,777,216

There are 16.7 million possible colors in a JPEG with a bit depth of 8 per color.

The bit depth of the entire file is 24 (8 + 8 + 8).

Advantage of 16-Bit Raw Files

Raw files may have a bit depth of 16, for a total bit depth of 48 for a file.

Each color has 65,536 possible combinations-compared to the 256 of a JPEG color.

Take the number of possible combinations for each color, 65,536, and multiply them together.

65,536 x 65,536 x 65,536 = 281,474,976,710,656

There are 281 trillion possible colors in a raw file with a bit depth of 16 per color, or a bit depth of 48 for the entire file.

With all of that data, you can do extensive editing, especially in shadow areas, without the loss of quality that would occur when editing a JPEG file.

Bytes, Kilobytes, & Megabytes

Definitions

Bytes, kilobytes, and megabytes are measurements of the size of photography files.

A byte is the smallest unit of measurement.

There are a thousand bytes in one kilobyte.

In turn, there are a thousand kilobytes in one megabyte.

That's 1,000 x 1,000 = 1,000,000.

Because a kilobyte has a thousand bytes, multiplying it by a thousand equals 1,000,000 bytes.

One Kilobyte One Megabyte
1,000 bytes 1,000,000 Bytes

You may encounter slightly different amounts.

Sometimes, instead of 1,000 and 1,000,000, 1,024 and 1,048,576 are used.

One Kilobyte One Megabyte
1,024 bytes Bytes Bytes

These numbers are actually more accurate.

Saving

Large files require more time to be saved to your memory card after you press the shutter release.

This can be an issue if you're taking many photographs in quick succession.

Many cameras have a burst mode to facilitate this activity.

Megapixels & Pixel Dimensions

Megapixels

Megapixel is the measure of the devices that collect the photons, to make pixels, on the camera sensor.

One megapixel is one million of these devices.

So, one megapixel will produce one million pixels.

For example, a photograph from a thirty-six megapixel camera will have thirty-six million pixels.

Pixel Dimensions

The pixels are arranged in a rectangular array called the pixel dimension.