Pixel-based images

Pixel-based images, also referred to as Raster graphics or Bitmaps a made up of small squares or dots known as pixels. A pixel (pixel-element) is the smallest editable element in a pixel-based image. A pixel-based image may be stored as a number of file formats such as a jpeg, png, gif, tiff or psd. Unlike Vector based imagery, pixel-based imagery is resolution dependent and can not be scaled up without loosing quality. Resolution is typically measured by the number of pixels per inch (ppi). The higher the number of pixels per inch the higher the image quality will be and the larger the file size will become. Each pixel in an image has a position on the document and an RGB value. By altering the RGB values and positions of various pixels in an image using a pixel editing program such as Adobe Photoshop, we can retouch and alter an image in a vast variety of ways. All digital photographs are pixel-based as are the majority of of images within a web page.

This video takes an imaginary journey into the land of the pixel:

Uploaded by onemoreprod. – Watch original web videos.

Image retouching with Photoshop

(See more “Celebrities Before and After Photoshop“)

The majority of images we see these days have had some level of digital alteration. It may be to simply correct the photographic aspects of the image (lighting, colour, sharpness, perspective etc) or may take the image to a level far beyond that which the camera captured. Although our image editing tools are much more sophisticated today, photographers have been altering their images since the early beginnings of the craft.

Digital image retouching with tools such a Adobe Photoshop allows us to elegantly alter every aspect of the image. From the simple removal of a blemish to a complete reconstruction of the bodily or facial form the original image captured by the camera can now take a radical and convincing departure.


This article from Smashing Magazine collects a large range of tutorials for techniques commonly used for Glamour Retouching. (Note the ethics discussion that ensues.)

This article in Inspired Magazine opens a discussion on the realities and ethics surrounding the practice.

This video from Adobe TV shows the basics of blemish retouching:

Understanding Resolution

The term resolution refers to to the amount of information in an image.
Devices such as digital cameras, printers, scanners & monitors all have a particular resolution.
Image resolution is measured by the amount of Pixels Per linear Inch (PPI) or Dots Per Inch (DPI) if referring to print resolution.
The more pixels per inch the higher the image quality (and the larger the file size will be) .
High quality print resolution is typically 300ppi. 300ppi is roughly the limit of what the human eye can distinguish.
Monitor resolution varies greatly depending on the device (from a 19ppi TV to a 340ppi mobile phone). Find the PPI of your monitor in this Wiki entry.
Unlike when printing, an image will be displayed on a monitor pixel to pixel so will change size depending on the devise.

Here’s a pretty simple breakdown of resolution.

Here’s a well written and relatively easy to grasp explanation.