What Is With All These File Formats?
Overview of handling photographic files
You will use an application like Photoshop, Photoshop Elements, or iPhoto to work with your picture files. Read their manuals, but those books often describe features beyond our needs. Our recommendation is to stick to the elementary tasks outlined on these four pages.
- File formats (uses, benefits, and conversion of different file formats)
- File formats revisited (dots, pixels, resolution, and file conversion)
- Scanning photographs (using a scanner and generating a master file)
- Retouching photographs (alignment, cropping, color modes, light and contrast)
There are many file formats used in digital graphics, but I recommend you work with the best two traditional file formats: TIF and JPG.
There are two file formats that you will use when working with digital images:
- TIF (TIF, .tiff, or .tif) is the standard format of the printing industry.
- JPG (JPEG, .jpg, or .jpeg) is the standard from the electronics industries.
File integrity and compression algorithms
Because picture files are large, graphic formats offer built-in compression, making smaller files by discarding some information. The greater the compression, the more information is discarded. Compression algorithms are called “lossy” to indicate this loss of file information.
- TIF compression is called LZW, but its use is optional and should never be used. Without LZW, TIF files are lossless. Make sure that you keep LZW turned off in the Save As window.
- JPG compression ratios can be modified but not completely turned off. For this reason, JPEG is a lossy format. Make sure that your save as preference is for minimal compression.
When working with a picture file, you may need to save it several times before it is ready for its final purpose. To avoid needless compression and lossy saves, you should always use the TIF format for initial scanning, all intermediate steps, and final review.
Use JPG only at the final Save As step when the JPG format is required.
Formats for various end uses
- TIF should always be used in a file for printing on paper, with one exception: machines to make photographic copies use JPG files, so your final save as should convert the file to a JPG.
- JPG should be used when the final file will be uploaded to the Internet or embedded in a file for use on a monitor.
This article is one of several to help you document local history. Other articles will help you convert your interviews, documents, pictures, and artifacts into documentation of your local history that can be shared with your community.