Vector and Bitmap Graphics Info
- What is the difference between vector graphics and bitmap graphics?
- Where do vector graphics come from?
- Where do bitmap graphics come from?
- Can bitmap graphics be converted to vector graphics, and vice versa?
- What are the different types of bitmap graphics?
- What guidelines do you have for bitmap graphics resolution?
- Can I increase the size of bitmap graphics in a page layout application?
- Can I resize bitmap graphics in Photoshop?
- I've heard Encapsulated PostScript (EPS) mentioned in the context of both vector graphics and bitmap graphics. How can it be both?
- Can I copy a graphic and paste it into my document?
Q.
What is the difference between vector graphics and bitmap graphics?
A.
A vector graphic is defined in a mathematical nature, which makes it resolution-independent. This means it can be printed clearly at any size. Logos should always be vector. Photos cannot be vector.
A bitmap or raster image is formed by a grid of small squares, known as pixels. Each pixel contains data that describes whether it should be rendered as black, white, or a level of color. Bitmap graphics are resolution-dependent and can appear jagged or in loose detail if they are created at a low resolution and then enlarged or printed at a higher resolution.
Q.
Where do vector graphics come from?
A.
Vector graphics are typically created by illustration software such as Adobe Illustrator. They are most commonly saved as .EPS, .AI, or sometimes .PDF file types.
.JPG, .PNG, and .TIFF files cannot be vector.
Q.
Where do bitmap graphics come from?
A.
Bitmap or raster graphics are typically created by pixel-based image editing software such as Adobe Photoshop. Additionally, bitmap graphics are generated from digital cameras and scanners.
Photos are always raster. Logos generally shouldn't be.
Q.
Can bitmap graphics be converted to vector graphics, and vice versa?
A.
Yes. Software such as Adobe Illustrator may be able to convert bitmap images to vector images, though the final result may not be exactly as you expect. Some graphics or logos may be re-created as a vector file by our graphic design or prepress professionals.Contact us to discuss how best to accomplish what you need.
Vector images can be converted to bitmap images by opening them with Adobe Photoshop. Please note that converting a vector image to a bitmap image is rarely necessary, removes the resolution-independence of vector graphics, and should only be done if you have a very specific reason to convert the graphic. Make sure to save the bitmapped version with a new name - you want to keep the higher quality vector version as well!
Q.
What are the different types of bitmap graphics?
A.
A one-bit image refers to an image that is a solid color, with no shades of that color. A continuous tone image refers to photographic images, whether they are full color, black-and-white images with shades of gray (grayscale), or single-color images with shades of that color.
Q.
What guidelines do you have for bitmap graphics resolution?
A.
One-bit images require 600 pixels per inch (1200 preferred). Full-color continuous tone images, grayscale images, and single-color continuous tone images require 300 pixels per inch.
Q.
Can I increase the size of bitmap graphics in a page layout application?
A.
It is best to avoid scaling up images in a page layout application, as these programs have no ability to change the actual pixels in an image. Ideally your image will be 300 dpi at the final size it is to be printed* (type may be best at 600 dpi). A bit more is fine, though it may increase file sizes. Reducing the size of images is OK, but watch the resolution when trying to increase the size!
*For many wide format products a resolution of 150 dpi is sufficient, particularly if it is a banner or something that will be viewed primarily from a distance. Please contact us if you are unsure!
Q.
Can I resize bitmap graphics in Photoshop?
A.
To reduce the size and/or resolution, yes, absolutely.
To increase the size the answer is yes, sort of. Photoshop can increase the resolution of a low-resolution image, but increasing the resolution of an image scanned or created at a lower resolution only spreads the original pixel information across a greater number of pixels and rarely improves image quality. The image may go from pixelated to blurry, but is unlikely to improve. Try to start with the highest resolution image you can!
Q.
I've heard Encapsulated PostScript (EPS) mentioned in the context of both vector graphics and bitmap graphics. How can it be both?
A.
EPS files act as a container for transferring graphic information. When illustration software such as Adobe Illustrator creates an EPS file, it is a vector EPS. When pixel-based image editing software such as Adobe Photoshop creates an EPS file, it is a bitmap EPS.
Q.
Can I copy a graphic and paste it into my document?
A.
For photos, this is generally a bad idea. Copying a vector graphic from Illustrator to Indesign can work, but it is generally safer to save the graphic as an EPS and place it into your document.
While copy-and-paste is supported by most software, you will have much more predictable results by creating a link to your graphic. The graphic then remains outside of your document and is referenced as needed. Please refer to your software's documentation for full details about creating links to your graphics.