Image Preparation

• What is a Pixel?
• Image Resolution
• Image Size
• File Size
• File Types

What is a Pixel?
Images on the Web are displayed in pixel units. Your computer screen fits 72 x 72 pixels into every square inch of your screen. This is generally referred to as 72 dpi (dots per inch). Your eye blends the pixel colours together to recognize an image or to interpret text.

Here's an example of how it works:

Image at 72 dpi


In this sample it is difficult to see the individual pixels.

Portion of image magnified 600%

In this sample you can plainly see the pixels and how they blend to make the image.

Image Resolution

• Screen Resolution is 72 dpi (as previously discussed)
• Print Resolution is generally 350 dpi or higher.

So, what's the big deal?
As you can imagine, an image with colour information for 350 dots per inch has a much larger file size than the same image with colour information for 72 dots per inch.

Here is a chart that demonstrates the difference

1" x 1" image	72 dpi	350 dpi
File size:	7.1 kb	193 kb

Image Size
Just to make it more confusing, image size can refer to 2 different things:

1. Dimensions
   These are the physical dimensions of the image. Dimensions can be measured in inches, cm or pixels. The image above is xx pixels wide and xx pixels tall. You can find out what the dimensions of an image are by using an image editing program such as Photoshop or by right-clicking on the image file after opening it in Internet Explorer.
   
   
2. File Size
   The other important consideration is how much space the image will take up with regard to computer space or file size. For example, an image may be 12kb.
   

File Size

Image file size refers to how much space the image will take up with regard to computer space. For example, an image may be 12kb.

IMPORTANT! The larger the file size of images, the slower the download of your page!

Major factors that effect the file size of an image:

1. Dimensions
   The larger the physical dimensions of the image are, the larger the file size will also be.
2. DPI
   Make sure images are 72 dpi and you won't have any problems. Images with higher dpi will download much more slowly than they need to.
3. Quality of Image
   Often the quality of the image suffers if you try to squeeze the file size too small. It is a bit of an art to find the balance of the highest quality image with the lowest possible file size. With Power Site Factory you have plenty of space, so you don't have to worry about this too much!
4. File Types
   You can save your images as .jpeg or .gif files. In most cases .jpeg is better for photographic type images and .gif is better for graphical images with fewer colours.

A good file size to aim for - per image - is anything less than 100 KB.

File Types
Power Site Factory supports the two standard Web image types: .jpeg and .gif.

In most cases .jpeg is better for photographic type images and .gif is better for graphical images with fewer colours. "Better" meaning that the quality of the image will be higher and the file size will likely be lower.

Export or save your images in one of these formats before importing into your Power Site Factory Web site.