Digital Imaging Basics

Some applications work with words, others with images, others with numbers, others with sound, etc. The way that your computer knows what application works with what file is by the file extension. For example words might have a .doc or a .txt file extention. An example would be "MyBiography.txt" as a filename. A side note...folders Never have extensions and files Always have extentions.

When working with digital images you may be working with any of the following file types:

• .gif: This is a lossy file type that contains only 256 colors plus transparency. Typically not used for photographs but rather for images with few colors and sharp lines.
• .png: This also is a lossy file type that contains only 256 colors plus transparency. .png seems to be replacing .gif. In my personal workflow .png has replaced .gif. Typically not used for photographs but rather for images with few colors and sharp lines.
• .jpeg or .jpg: This is a lossy file type that is universally used for photographs. This file type includes 16+ million colors, no transparency, and adjustable compression. There are several important things to remember about .jpeg files: 1) Don't over-compress the images. Try to find the smallest file size without adding artifacts and/or causing un-necessary damage. As a default consider 50 to be a safe number. Artifacts (image ghosts) are common in over-compressed .jpeg images. Learn to recognize and to avoid .jpeg artifacts. 2) Each time a .jpeg file is saved the image deteriorates at least a bit. Ensure that your workflow does not include saving an image as .jpeg until the very last step (if needed at all).
• .tiff is lossless and universally used for photographs. This file type includes 16+ million colors, no transparancy, no compression. .tiff can include layers. The major difference between .tiff and .jpeg is that .tiff does no damage to an image and the file size is much larger.
• .RAW: This file type is not an image at all but rather pixel readings. Many photographers call a .RAW image a true negative. Raw files require a different workflow that is outside the scope of this class at this time.
• .psd (or 'native'): Each application has it's own default file type. Adobe uses .psd as it's preferred file type. Images should be worked with and saved using the 'native' file type (.psd) for Adobe whenever possible. It is from the .psd file that the final .tiff or .jpeg image can be fabricated.

If this seems like a lot of file types be relieved. There are over 50 image file types. You really need to work with only a few of the 50+ file types.

Also understand that the above files are 'raster' file types. 'Raster' file types are based on pixels. The other file type that you will run into are called 'Vector' file types. A vector image is mathematics instead of pixels. The advantage of a vector file is that it can be made huge or tiny with no loss of quality.