Adobe Photoshop

Introducing Photoshop 

Adobe Photoshop  is a powerful graphic editing program that allows you to create and 

manipulate images for print, the web, and other media. Photoshop is almost limitless in the 

ability to manipulate and edit images, but don't let that scare you! We have created this guide 

to help you learn and take advantage of the many feature of this program.

 Destructive Edits - These edits alter or change the image information. A destructive edit 

directly manipulates the image's pixels and therefore cannot or is very difficult to be reversed.

  Non-Destructive Edits - Edits that do not directly affect the image’s pixels until the image 

layers are flattened (by saving as a flattened image format or flattening layers), so one can 

make alterations using non-destructive tools without losing any image quality or information.

Computer colour management

COLOR MODEL

A color model is an abstract mathematical model describing the way colors can be 

represented as tuples of numbers, typically as three or four values or color components. When 

this model is associated with a precise description of how the components are to be 

interpreted (viewing conditions, etc.), the resulting set of colors is called color space. This 

section describes ways in which human color vision can be modeled.

RGB color model

Media that transmit light (such as television) use additive color mixing with primary colors of 

red, green, and blue, each of which stimulates one of the three types of the eye's color 

receptors with as little stimulation as possible of the other two. 

This is called "RGB" color space. Mixtures of light of these 

primary colors cover a large part of the human color space and 

thus produce a large part of human color experiences. This is 

why color television sets or color computer monitors need only produce mixtures of red, 

green and blue light. See Additive color.

Other primary colors could in principle be used, but with red, green and blue the largest 

portion of the human color space can be captured. Unfortunately there is no exact consensus 

as to what loci in the chromaticity diagram the red, green, and blue colors should have, so the 

same RGB values can give rise to slightly different colors on different screens

CMYK COLOR MODEL

It is possible to achieve a large range of colors seen by humans by combining 

cyan, magenta, and yellow transparent dyes/inks on a white substrate. These 

are the subtractive primary colors. Often a fourth ink, black, is added to improve reproduction 

of some dark colors. This is called "CMY" or "CMYK" color space.

The cyan ink absorbs red light but transmits green and blue, the magenta ink absorbs green 

light but transmits red and blue, and the yellow ink absorbs blue light but transmits red and 

green. The white substrate reflects the transmitted light back to the viewer. Because in 

practice the CMY inks suitable for printing also reflect a little bit of color, making a deep and 

neutral black impossible, the K (black ink) component, usually printed last, is needed to 

compensate for their deficiencies. Use of a separate black ink is also economically driven 

when a lot of black content is expected, e.g. in text media, to reduce simultaneous use of the 

three colored inks. The dyes used in traditional colorphotographic prints and slides are much 


more perfectly transparent, so a K component is normally not needed or used in those media.

GRAPHIC TYPES

Computer graphics are graphics created using computers and the representation of image data 

by a computer specifically with help from specialized graphic 

hardware and software.

The interaction and understanding of computers and interpretation of 

data has been made easier because of computer graphics. Computer graphic development has 

had a significant impact on many types of media and have revolutionized animation, movies 


and the video game industry.

VECTOR GRAPHICS

Example showing effect of vector graphics versus raster (bitmap) graphics.Vector graphics 

formats are complementary to raster graphics. Raster graphics is the representation of images 

as an array of pixels and is typically used for the 

representation of photographic images. Vector 

graphics consists in encoding information about 

shapes and colors that comprise the image, which 

can allow for more flexibility in rendering. There 

are instances when working with vector tools and formats is best practice, and instances when 

working with raster tools and formats is best practice. There are times when both formats 

come together. An understanding of the advantages and limitations of each technology and 


the relationship between them is most likelytoresultefficientand effective use of tools.

RASTER GRAPHICS

Raster graphics are digital images created or captured (for example, by scanning in a photo) 

as a set of samples of a given space. A raster is a grid of x and y coordinates on a display 

space. (And for three-dimensional images, a z coordinate.) A raster image file identifies 

which of these coordinates to illuminate in monochrome or color values. The raster file is 

sometimes referred to as a bitmap because it contains information that is directly mapped to 

the display grid.

A raster file is usually larger than a vector graphics image file. A raster file is usually difficult 

to modify without loss of information, although there are software tools that can convert a 

raster file into a vector file for refinement and changes. Examples of raster image file types 


are: BMP, TIFF, GIF, and JPEG files.