Images can be saved in different file formats. The most widely used we will use in class:
.psd:(working document) This format is a Photoshop-native document, which means that it was created for the application itself. When you save a file as a PSD document, you'll be able to retain layers, channels, paths and every other attribute that can be applied in Photoshop.
.jpg:(finished/printable document) a commonly used method of lossy compression for digital photography (image). The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. is the most common image format used by digital cameras and other photographic image capture devices.
.tiff:(finished/printable document) One of the most common formats for Photoshop users is the TIFF format. A TIFF (Tagged Image File Format) is the most widely used printing format on both Macintosh and PC platforms. Not only that but there are few compatibility issues, because most graphic programs will identify a TIFF and interpret the file correctly. So, if you want to print an image, the TIFF format is the best choice.
.png: (for web use) Common file format when saving for web viewing. This is a lossless format that creates a smaller size image without losing quality and supports alpha transparency when saving in photoshop.
File Sizes Digital files all have sizes that are measured in Bytes. To the right is a file size chart, from smallest to largest.
The smallest size is a Byte. 1024 bytes make up 1 KB. 1024 KB make up 1 MB and so on.
When saving a file for web use, the file should be in the KB range. For printing, it should be larger (thus better quality).
Image Resolution
Image resolution makes up the file size as well as the file quality.
Resolution is measured by dpi (dots per inch). (In Photoshop, when setting up a file it's called pixels per inch). The more dots (pixels) of color in one area, means the clearer and better quality the image will look. (see image to the right)
The higher the resolution (the higher the dpi) the larger the file size will be. (The lower the dpi, the smaller the file size will be).
An image file used for the web should be 72 dpi
An image file used to print should be 300 dpi or higher
Here is an example of an image at "High Resolution" (300 dpi) vs. "Low Resolution" (72 dpi)