In the last video, we discussed the most common image file formats used by graphic designers. In this video, we will categorize those formats into two main types, raster image files and vector image files. The main difference between these files being what the images are composed of. Vector images are composed of paths or lines, whereas raster images are composed of pixels or dots. But why is this distinction important? Let's start by taking a closer look at raster images because since they are based on pixels, they are more common to most people. Why is this? Because all the photographs we take are translated on our computers and smart phones to tons of pixels or dots. So what exactly is a pixel? If you've ever looked close up on any electronic screen or at a photograph honest screen, you may have noticed a large number of tiny dots or squares. These dots are called pixels, which is short for picture elements. These pixels are dots in a raster image are arranged in a matrix or grid much like graph paper. A pixel can be solid black or white or varying tones of gray. They can also be any colors added to form an image. But unlike vector images, when combined together, thousands of pixels in a raster file form a full picture we see on the computer screen. Raster image has four basic characteristics, resolution, dimensions, bit-depth and color mode. The number of pixels in a given distance is the resolution of an image. The physical size of these pixels changes according to how many fit in a given space. This is described in terms such as DPI or dots per inch or PPI, pixels per inch. The higher the number of pixels per inch, the smaller the size of each pixel and the more detailed an image becomes. An image dimension can be expressed in inches, centimeters, dots and so on. This measurement also can be described in pixels, such as 600 pixels per inch by 400 pixels per inch. The higher the dimension, the larger the picture size. Bit-depth refers to how many tones or colors each pixel in a raster image can have. Each pixel in a raster images is composed of lots of little bits, the more bits an image has, the more gradients and shades of color it will have. The color mode or color model of an image file is divided into two main categories, CMYK or RGB. Printed publications combine four colors; cyan, magenta, yellow and black to create what appears to be a broader range of colors. This is known as the four-color printing process. Whereas your computer or television monitors use different combinations of red, green and blue light to display color, this electronic color mode is called RGB. Each of these characteristics effects the size of the electronic file and the clarity of the image. The size of a graphics file also affects how long it takes to print or even download an image. The larger the image file the, longer it will take to print or download, as well as how much space required to store the image on your computer or your smart phone. Relating this back to the most common image file formats used by graphic designers, raster image files are BMP, JPEG, GIF, TIFF and PNG because they are composed of pixels. But now let's switch to vector images, such as EPS files. So as we have discussed, raster images are composed of pixels, they are created from sources such as cameras or scanners or within some computer programs such as Photoshop. On the other hand, vector images are made of thin lines and curves known as paths. These image file formats containing mathematical geometric description that can be rendered smoothly at any display size and are usually created in programs such as illustrator. Basically, vector information describes an image in terms of lines or curves and shapes, rather than in pixels, squares, or tons of small dots as in the case with raster images. As this image shows, because vector images are made of lines and not individual pixels, they can be enlarged or reduced without affecting their appearance. I like to think of the lines of a vector images kind of like stretching a rubber band. But to resize raster images pixels need to be added to fill in the space, much like how bricks need to be added to extend a wall or build a house. When these bricks or pixels are added, it can give some images a jagged look. Vector images also known as object oriented images use x and y coordinates to help determine the position of points and lines. Luckily for us, graphic design programs such as illustrator have a series of mathematical equations built in to program that help determine a line's direction, thickness and polar. A vector is based on several parts, anchor or starting points, angles or directions, paths or strokes, and line length. Strokes are created through a series of connected and unconnected anchor points, look like little dots on the screen there. Angles are directions or curves created by curved anchor points. You can see how these two lines are curved around that one anchor point. The path or stroke is the entire outline of the shape. The length of the line is mathematically determined to help draw a shape. Vector files also have edible attributes such as color, fill and outline. As this image shows, you can enlarge and shrink vector images without affecting their display or print resolution. Vector images are usually saved as EPS files for working in page layout programs such as InDesign. Vector files also maintain a transparent background when transferred between applications. It is these factors that make vector files ideal for creating logos, illustrations, entire font families and precise typographic. Some other factors to keep in mind is that you cannot scan an image or save it as a vector file without using special software. You can however easily convert a vector file to a raster file in Adobe Illustrator. But if you open a vector file in a raster based programs such as Adobe Illustrator, the file will automatically be rasterized because that is what the program is based on. Thus it will lose all the crisp and sharp lines and edges that it offers in Adobe Illustrator. Remember, Photoshop is based on pixels, not lines or path. Again, this is why logos need to be made in Illustrator and saved as EPS files and not made in Photoshop. They'll just be much clear to read and easier to open other design programs if you use Illustrator. However, some people find Photoshop to be well quote an easier program to learn, but my advice is to find another designer if that person insist on creating a logo for you in Photoshop. You want logos to be created in Illustrator and then saved as EPS files. So again, in this video remember, vector images are composed of paths or lines. They are used in Illustrator or they're created in Illustrator and are best for creating logos, line, drawings or illustration. They can then be moved and used in any other Adobe Suite programs and online. Raster images are composed of pixels or dots. They are created in Photoshop and are best for creating design pieces based on photographic images.
