Raster vs Vector
There are two type of images. Raster and Vector. Raster images are more common in general such as jpg, gif, png. Vector graphics are common in graphic design. Also used for CAD and professional drafting industries which we do not provide information nor services for.
When using a raster program you paint an image and it's similar to dipping a brush in paint and painting. You can also blend colors to soften the transition from one color to another.
When using a vector program you draw the outline of shapes: e.g. an eye shape, a nose shape, a lip shape. These shape objects can be filled with one single color**
A lot of images can be made with either raster or vector program and look exactly the same on both programs. Images with a subtle gradation of one color to another are the images that will look most different since vector program need to create a separate shape-object for each shade of color.
Some vector programs do have the ability to create color gradients but these are raster effects within the vector program. Any process that must have 100% vector or true vector cannot have any raster effects.
Photographs are probably the best examples of images completely made of color blends - or shade blends in the case of black and white photographs - and those images look very different when we draw them in vector format. Click here for examples.
Pixels vs Vectors
Raster images are made of pixels. A pixel is a single point or the smallest single element in a display device. If you zoom in to an image you will start to see a lot of little tiny squares.
Vector images are mathematical calculations from one point to another that form shapes. If you zoom into vector graphics it will always look the same.
You cannot always see the difference between a pixel and vector image at a glance. I've magnified a sample below to get a visual understanding.
An existing raster image has a specific number of pixels, when you enlarge the image without changing the number of pixels, the image will look blurry. When you enlarge the file by adding more pixels, the pixels are added randomly throughout the image, rarely producing optimal results.
Vector graphics do not have a specific number of pixels on each file but rather the graphics are made of shapes. These shapes are math formulas. When you enlarge a vector graphic the math formulas stay the same rendering the same visual graphic no matter the size. The quality never changes when vector graphics are scaled.
Vector graphics are made of mathematical calculations that form objects or lines - because they are not composed of pixels they are resolution-independent.
Vector graphics can be enlarged and printed at ANY SIZE!
Instead of pixels, vector graphics use shapes and lines to represent images. Vector graphics can be scaled to any size without losing quality.
Vector graphics color editing
Vector graphics can include a large or a limited amount of colors. It is also easy to change a multi-color image to a limited color image using a vector program. Limited colors are required by some processes such as embroidery, "stencil-cut" vinyl signs, and specialty promotional items (such as logos printed on cups, pens, bottles, etc.)
Vector Outline or Wireframe
Some Vector programs have two different views; preview/normal view which displays the image as we normally would see it and an outline/wireframe view which displays the vector outline of every object in the file. This vector outline/wireframe is important to some companies like engraving & vinyl-cut signs because it guides the equipment they use to create their products.
For categorizing purposes I have named the above: photo-realistic vector, vector illustration, and vector lineart.
1. Photo-realistic vector: a photograph was traced as vector using a multitude of colors to allow the image to have a closer resemblance to original. This vector image can be used in many different processes like CMYK or digital printing, but as you can see from the outline/wireframe view, there are too many objects for it to work for engraving or vinyl-cut signs, embroidery or any other process that is guided by the vector outline. Photographs are best printed as they are: raster images... Learn more.
2. Vector illustration + raster effects. This is a hand-drawn, simplified illustration. Color blends can be created in vector programs but they are actually raster effects so this image is NOT 100% vector. The raster effects show up as boxes on the outline/wireframe view. This vector image is suitable for many processes except those that are guided by the vector outline such as vinyl-cut signs or engraving..
There are other ways to achieve color blends, please see traced vectorization of images with color blends
3. Vector "line art". This is 100% vector art; NO COLOR BLENDS. The outline/wireframe is acceptable for all processes including those that are guided by the vector outline.
Vector Graphic Summary
- Made of mathematical formula shapes and lines that can be scaled to any size
- Common vector graphic file format: ai, cdr, svg, and eps & pdfs originating from vector programs
- Common vector graphic programs: drawing programs such as Illustrator, CorelDraw, Inkscape (free)
- Common vector graphics: logos, illustrations, technical drawings
- Required by some processes such as engraving, cut signs and specialty items
- Used in CAD and drafting industry
* eps and pdf files can originate from either raster or vector programs, and/or can include raster & vector elements. Is EPS Vector?
Pixel-based images represent and edit photographs and photo-like images with continuous tones better than vector programs because they can use an abundant number of different color pixels. By arranging pixels and slowly incrementing or changing the color or shade of the pixels adjacent to them, it creates a subtle gradation from one color to another: nice and smooth color blends.
Raster images' dimensions are measured in pixels. Because raster images cannot be enlarged without losing quality, different suppliers have specific size requirements for their processes; they require a specific pixel resolution: a specific amount of pixels within each inch. The amount of pixels within each inch in the image represents the image pixel resolution or ppi (pixels per inch).
How large a raster image can be printed - and maintain quality - depends on 2 things:
- the pixel dimension of the image (e.g. 6824 pixels wide by 2345 pixels high)
- the pixel resolution: pixels-per-inch (ppi), how many pixels per inch are required by the particular printer
Some offset printers (paper printing) require a minimum of 300 ppi
Some screen printers (cloth printing) require a minimum of 240 ppi
Large format printers (banners, billboards) vary a lot because it also depends on the distance from which the sign is going to be viewed - could be as low as 20 or more than 200
Multiply the resolution required by the area to be printed. Examples:
If a printer requires a minimum of 300 ppi and you want to print an image in an area that is 5 inches wide, multiply 300 pixels x 5 inches (300 x 5 = 1500). Your image must be at least 1500 pixels wide.
If a printer requires a minimum of 240 ppi and you want to print an image in an area that is 12 inches wide, multiply 240 pixels x 12 inches (240 x 12 = 2880). Your image must be at least 2880 pixels wide.
Raster images have a certain amount of pixels within each inch. A 72 ppi image has 72 pixels in every inch. A 300 ppi image has 300 pixels per inch. Usually the higher the ppi, the higher the quality. When you are required to provide a large or high resolution image file, the file must have been created or scanned at a large size (both the dimension and the resolution required.) E.G. if you need to print an image at 2 inches wide and 300 ppi is required, your image must be created, photographed or scanned at a minimum of 600 pixels (2 in x 300 ppi).
Once the image is created at a certain dimension, you may not be able to use this image at a larger size without losing quality. When you manually increase the resolution with a program like Photoshop, Photoshop randomly adds pixels and the result will most likely be a high resolution image of poor quality.
Sample of a raster image below:
Divide the pixel dimension of your image by the resolution required by your printer.
To open and edit an image pixel dimension you must use a photo-editing program like Photoshop, PaintShop Pro, or GIMP (free)
If image is 1024 pixels wide & printer requires 300 ppi (1024 ÷ 300) = image can be printed at 3.413" wide
If image is 1024 pixels wide & printer requires 240 ppi (1024 ÷ 240) = image can be printed at 4.266" wide
Raster Image Summary
- Made of pixels. Image must be created/scanned at the desired printed size or larger for good quality
- Common raster image files: jpg, gif, png, tif, bmp, psd, eps and pdfs originating from raster programs
- Common raster programs: paint programs like Photoshop & Paint Shop, GIMP (free)
- Raster images are the most common image type
It depends on the design itself. If it's going to have photographic elements with continuous tones and blends of color, you are probably better off using a paint program like Photoshop which is a raster program that specializes in photo editing, or use any other PAINT program.
If you want your final design to look like a drawing or illustration, with clear contrasts between the elements of the design, then use a vector program.
Ideally a company that has a logo design with photographic elements, also has a secondary simplified version of their logo in vector format that can be used for those specialty items that require vector art such as plotters, engravers, vinyl-cut signs, promotional specialty items (cups, pens, bottles with company logo) Sample below:
Raster & Vector Summary
• Mathematical calculations that form shapes
• Vector programs best for creating logos, drawings and illustrations, technical drawings
• Can be scaled to any size without losing quality
• Resolution-independent: Can be printed at any size/resolution
• A large dimension vector graphic maintains a small file size
• Number of colors can be easily increased or reduced to adjust printing budget
• Vector art can be used by many processes and easily rasterized to be used by all processes.
• Can be easily converted to raster
• It is not the best format for continuous tone images with blends of color or to edit photographs
• Common vector graphic file format: ai, cdr, svg, and eps & pdfs originating from vector programs
• Common vector programs: drawing programs such as Illustrator, CorelDraw, Inkscape (free)
• Made of pixels
• Raster programs best for editing photos and creating continuous tone images with color blends
• Do not scale up optimally - Image must be created at the desired printed, or usage, size
• Large dimensions & detailed images equal large file size.
• It is more difficult to print raster images using a limited amount of spot colors.
• Some processes like engraving, stencil-cut signs, etc, cannot use raster formats.
• Depending on the complexity of the image, conversion to vector may be time consuming.
• Raster images are the most common image format: jpg, gif, png, tif, bmp, psd, eps and pdfs originating from raster programs
• Common raster programs: photo editing / paint programs such as Photoshop & Paint Shop, GIMP (free)
DPI - Dots per Inch
This is the amount of ink dots the printer will put on each pixel of your image. The DPI is set by the actual printer device and it is not something in the image for the graphic designer to manipulate.
PPI - Pixels per Inch
Digital raster images are measured in pixels, or picture elements. How many pixels per inch is determined by the device you create the digital image with: camera, scanner, or graphics software and can be modified with a photo/paint editing software.
*The information on this website is for graphic design and does not include CAD. The vector graphics we prepare are mainly for the graphics industry: printers, sign-makers, engravers, web and graphic designers. We do not offer information or services for CAD or drafting industry.
**Color gradients can be used within the vector program to allow for different colors within one single shape-object. These color blends and gradients are raster effects and images containing these gradients or any other raster effect is not considered 100% vector or "true" vector graphic.