File and Graphic Types
File Type Extensions
JPG: Generally the best option. It's high-quality and the file size is small. But beware: each resave slightly reduces the visual quality. It's great for photographs on the web, fine for printing.
TIF: Highest level of visual quality, but large file size. Great for image printing.
PDF: Standard portable document file. PDFs maintain image quality and are compatible across many platforms. They print well, but be cautious of color changes from screen to print.
GIF: Contains just 256 colors (compared to millions within a JPG). Best for simple online graphics. Do not print a GIF.
AI: Adobe Illustrator file. Best for logos and illustrations. For Johnson Plotter, convert to PDF or JPG to print. For the Library/BiHall Plotter, printing an AI is fine.
PNG: Similar to the JPG but larger and higher quality. Good for logos because background is transparent.
BMP: Stores digital files. Don't use this for print media.
SVG: Scalable Vector Graphics are images based on XML text files - this means they are 2-dimensional images defined by a sheet of code. Because they are text-based they have the ability to be animated or made interactive. It can be printed, but other forms are advisable.
RAW: Uncompressed file, no effects. This is the highest quality photograph/picture file format. Most programs and browsers cannot display RAW; requires further editing.
Vector: The lines and curves of vector images are defined by mathematical objects called vectors. They are resolution-independent so you can move or modify the graphics without losing detail or clarity (they won't become pixelated because they do not rely on pixels). Vector graphics are great for artwork that will be used at various sizes and in various output media.
Vector File Types: AI, EPS, PDF, SVG
Raster: Raster images are represented by pixels. You edit these pictures by the pixels rather than by objects or shapes. They are resolution dependent because they contain a fixed number of pixels, so they will lose detail if scaled too large (on screen) or printed at a resolution that is too low.
Raster File Types: JPG, PSD (Photoshop), PNG, XCF
Never try to print .psd files. It's too much for the printer to register and it will be attempting to print for an hour.
Tips and Considerations
What is COMPRESSION?
Compression is the reduction of file size, as from 1 GB to 500 MB. Most graphics are too large to be downloaded quickly in their natural state, so they are often compressed before being put on a website, etc.
Things to Consider with File Types:
- What type of image are you working with?
- How small are large do you want your image file to be?
- Will your image need to be available in a variety of sizes?
- How do you want your graphic to download?
Web vs. Print resolution
Images for the web only need a resolution of 72 dpi (dots per inch). This is the maximum resolution of monitors. Images for print only need a resolution of about 300 dpi. Anything greater will not make much of a difference and anything lower will result in the loss of some quality.
Always start off with the highest quality image possible.
If the printer you're working with doesn't recognize a font you've used (it'll pop up with a dialog box if this is the case), use Adobe Illustrator to save the text box in "Outlines" (Right Click on text box > Create Outlines). This saves the text as a graphic, so printing will no longer be a problem.