Raster or Vector images in Technical Manuals?
The most basic question which I had faced while working is, do we need to use a raster image or a vector illustration for use in manuals. This is an important decision one makes in during Digital Document Lifecycle (DDLC), as it helps to better serve the purpose for the understanding of the component or task.
What are Raster and Vector image file types?
Basically, raster images are composed of pixels. Now, a pixel is basically a tiny square dot containing a color fill. Suppose we have a photograph we open it in Photoshop or GIMP and zoom it. We can see that the photograph is actually made up of lots of square dots, thousands of them. Let’s take a 1 inch x 1 inch area and count the number of dots inside it (not literally :P) this is known as the resolution of the image and it is measured as a number of Dots Per Inch in our jargon DPI. So it’s a simple calculation, the more the number of dots in a square inch of image area the sharper is the image. High resolution is what we call it. So raster images are either Hi-Res or Low-Res. We cannot take a Low-Res image and make it into Hi-Res just like that by stretching it and expecting the quality to remain the same. We cannot add more pixels to improve it just like that. Raster graphics, become “blocky,” since each pixel increases in size as the image is made larger.
Vector images on other hand are based on geometrical primitive shapes and mathematical equations that result in a shape. It is composed of paths, or lines, that are either straight or curved. The data file for a vector image contains the points where the paths start and end, how much the paths curve, and the colors that either border or fill the paths. Because vector graphics are not made of pixels, the images can be scaled to be very large without losing quality.The advantage of the vector is that it can be stretched without losing any quality. A good example will be a font in Word processor. We start at 12 pt. and we can increase it to any pt. size and it still stays sharp.One more application is in Logo creation. We start making the logo in a Vector software like Illustrator and then we can scale it up and down as required. The quality will look the same on a business card as it will on a billboard.
For Vector major applications we use are Adobe Illustrator, Inkscape, CorelDRAW, IsoDraw, Tech-Illustrator, AutoCAD. The common filetypes are AI, CGM, ISO, TI, CDR, DWG, DXF, EPS and SVG.
For Raster major applications we use are Adobe Photoshop, GIMP, MSPaint. The common file types are JPG, TIFF, PNG, GIF, BMP.
With regards to the proper application of these image types — We come across two document types for product domain — Marketing & Technical. Marketing publication connects the company with the market and the technical publication is meant for the employees of the company and the customers too. Both these publications depend heavily on illustration design and require the attention of graphic illustrators like us. The tech manual instructs the technician to assemble or replace a particular component in a machine whereas the marketing document (e.g Tech Specs and Sales Brochure) educates the customer on a product and it merits. As per the industry trend, the images should be a vector for technical manuals and raster for marketing documents. The reason being, vector images are black and white line art. They convey technical data hence, need to be accurate. Also, black and white line art keep the printing costs low. It avoids misinterpretation of technical data.
Deciding Factors for Raster and Vector
- Who will be the intended audience and purpose and use of the manual?
If the manual is to be used for Sales and Marketing purposes, product photographs and images will make the reader visualize the product better. Exact clarity can be a bit overlooked. Better to have a perspective view of the product. On the other hand, if the manual is to be used for technical purposes vector illustrations are a safe bet. They are easy to scale and reproduce than images. They provide a very great clarity regarding the product. - How many man-hours will be required to create the manual?
Using images in manuals is not time-consuming at all, as the author will insert the image in the correct frame. If there is an editing of the image required it will be a time-consuming venture. But, for illustrations, initial lead time in creation will be high. It is like a one-time investment with editing being an easy thing for vector illustrations. - How much will it cost (images / illustrations)?
This is again an important factor. Companies don’t want to end up using the revenue to keep re-modifying the images for each and every campaign. Images are difficult to modify. Images undergo compression each time we export them, losing their clarity over time. Illustrations being vector can be modified easily consuming less time and man-hours are saved leaving the resources to do other productive activity.
It is best if the company has the 3D model available with them. It increased productivity, quality and efficiency for creating vector illustrations. For printing purposes, having B/W line art is a cost-saving and it gives an easy idea to the viewer. - What will be the required expertise?
Here is where the Tools like Adobe Illustrator, IsoDraw and Photoshop come into play. There is an initial investment on tools required to get the job done. It is good to have an in-house team of expert illustrators with a creative bent of mind. Even better to have access to Design department’s CAD models. CAD models save the time required in the creation of illustrations. Images made using CAD models are consistent throughout. - File size constraints
A Microsoft Word file with 400 words can be about 40 KB. But an image will be 400 KB and a vector will be lesser till 200 KB. We have the freedom to simplify vector just enough to convey the idea. The basic rule of thumb I follow is a vector file should not exceed 200 KB.
Vector and Raster attributes
Concluding this, it is always a good choice to go for vector illustrations for Technical Manuals. They save project cost and time as they are easier to revise than raster.
