Resolution is the fineness of detail in a raster/bitmap image which is measured in ppi.
The combination of pixel dimensions and resolution (ppi) determine the amount of image data. So, two numbers are always needed. Unless an image is upsampled / resampled, the amount of image data remains the same as you change either the pixel dimension or resolution. In the first two images following, the size in inches has changed but the overall file size has not, since 'resample image' is unchecked. In the third, the resample is box is checked so the file becomes larger.


res 2

res 3

Increasing file size in Photoshop is not recomended. The added pixels do not increase detail, they are copies of existing pixels. A too small file will be pixelated, adding pixels will just make it blurry.
Dots per inch originated with dot matrix impact printers. RIT would prefer that dots per inch be defined - as resolvable spots per inch. We prefer to use pixels per inch. We don't want to see them and, given a reasonable file (150-300 ppi), our equipment is continuos tone.

For those of you who are semantics fans out there, or perhaps you thought the nerd you were listening to, had a lisp - They have changed, complicated and further confused the language. Officially now a Gigabyte is 1,000,000,000 bytes or 1000 bytes cubed. A Gibibyte (GiB) is 1024 bytes cubed. The relationship is the same for Megabytes and Mebibytes (MiB). People like round numbers Computers count in exponents (2-4-8-16). So when you next listen to a sales person, bite your tongue and give them a break.

More...than you wanted to, know.---------The following is a lexicon of un/common computerese

1 megapixel =1 million pixels
150 lpi (offset printing) = 300 ppi
8k    = 8192 pixels x 5460 pixels      = 100 lines per/mm     
Res 80 = 80 pixels per millimeter     = 20K.    There are 25.4 millimeters per inch.


1 bit = a single digit, either 1 or 0 (b)
4 bits = 1 nybble (?)
8 bits = 1 byte (B)
1024 bytes = 1 Kilobyte (KB)
1024 Kilobytes = 1 Megabyte (MB)
1024 Megabytes = 1 Gigabyte (GB)
1024 Gigabytes = 1 Terabyte (TB)
1024 Terabytes = Petabyte (PB)
1024 Petabytes = Exabyte (EB) 1,000,000,000,000,000 bytes

Common prefixes:
- kilo, meaning 1,000. (one thousand) (Kilometer, 1,000 meters)
- mega, meaning 1,000,000. (one million) (Megawatt, 1,000,000 watts)
- giga, meaning 1,000,000,000 (one billion) (Gigawatt, 1,000,000,000 watts)
- tera, meaning 1,000,000,000,000 (one trillion)

Color Management


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