Pixel

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The word pixel [pick sell] comes from two words: picture = PIX and element = EL
a pixel is the smallest part of a digital image

It’s a single coloured square.

How do we create pixels?

Using a scanner
Digital camera
create an image on screen using specialist software e.g. adobe Photoshop

Digital images are always rectangles (or are square).
They are constructed of pixels.
There is a horizontal number and a vertical number of pixels. When you multiply these two numbers, you get the pixel size of the image.
A million pixels is called a megapixel.
For example, an image that is 2048 pixels wide and 1536 pixels high = 3.145.728 pixels, called a 3-megapixel image, a very common image size used with digital cameras.

So what resolution do you need?
There are a million theories on what the optimum resolution is, here are my top tips;

  1. Before you do anything, KNOW YOUR OUTPUT.
    in other words you are going to use the image for:-
    a) screen
    b) print
  2. Know your dimensions.
    If you are creating an image to display on screen. What size will it be? Will it be full screen, half screen, etc
    if you’re going to print the image, it is going to be A4 A3 A6”x 4” photograph etc.
  3. Caution, the bigger the dimensions, the bigger the file size (memory)

The 3 resolution figures you’ll ever need to remember are;

Traditionally:

72 PPI for anything on screen
300 PPI for anything printed

Realistically:
You simply need to know the physical PPI: the PPI that a physical screen actually provides.

72 PPI

Traditionally this resolution was used for anything that was to be displayed on a monitor screen.
For example:
On a website, a power point presentation, TV screen, anything that doesn’t require a quality printout.

The PPI of a computer display is related to the size of the display in inches and the total number of pixels in the horizontal and vertical directions. This measurement is often referred to as dots per inch, though that measurement more accurately refers to the resolution of a computer printer.

PPI is affected by the dot pitch of the screen:

The dot pitch of a computer display determines the absolute limit of possible pixel density. Typical circa-2000 cathode ray tube or LCD computer displays range 67-130 PPI.

Resolution of mobile devices:

Apple iPhone 4:326 PPI.
HTC touch diamond: 286 PPI.
Google nexus one: 252 PPI.
Apple iPad: 132 PPI.

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