Graphics File Formats

The following are some image formats that can be saved from within Photoshop, using the "File --> Save As" command. JPG, GIF, and PNG formats can be previewed before saving if you use the "File --> Save for Web and Devices" command.

• PSD
  Photoshop Document. These can contain Photoshop layers and other information, like saved selections, etc. Pros: Helpful for working in Photoshop. Cons: Cannot be shared with friends unless they have Photoshop installed; if your friend has an older version of Photoshop installed, they might not get to use all the "goodies" that you do.
• JPG or JPEG
  Joint Photographic Experts Group. These are the standard for sharing photos over the internet. Pros: JPG files are very small in file size and yet can display many colors. Cons: In order to produce a small file size, JPGs are "lossy," meaning they lose information (pixel color data) when saved. Be careful to use high quality settings when saving as JPG.
• PNG-24
  Portable Network Graphic, 24-bit. 24-bit means that this format can display 16.7 million colors, like JPG. Not as well-known as JPG, but very useful. Pros: PNG files are "lossless," meaning no color data is lost when you save (as opposed to JPG). They can also store transparency information, meaning you are not limited to rectangular-shaped images. Cons: Lossless filetypes like PNG are typically larger in file size (sometimes by more than 10x) than JPG files, unless you're working with non-photographic data containing flat colors without lots of blended colors (some patterns, logos, etc.).
  Note: Don't use PNG-8 format unless you know what you're doing. PNG-8 has the same limitations as the GIF format, below.
• GIF
  Graphics Interchange Format. Not the best choice for most users unless you are creating animations or using images with few colors in the first place. Pros: GIF files are tiny in file size, and can contain multiple images in one file for displaying animations. Cons: GIF files are typically very bad for saving photos, since they can only display 256 colors. You can turn on a feature called "dithering" to help with this; it will make your image look "better" but not quite as good as PNG or JPG.
• BMP
  Bitmap format. Typically used for Microsoft Windows wallpaper images and clipart. BMP is not terribly useful and suffers from large filesize since it does not attempt to compress images.
• TIFF
  Tagged Image File Format. TIFF files (which are lossless) are seen less and less these days, but they are still used in the print industry and other places. TIFF is handy because it supports features like multiple-page documents and other conveniences, but not all software that opens TIFF files can use these features.
• TGA
  "Targa" format. These are commonly used in 3D video games because of the format's simplicity. Otherwise TGA files are rarely seen anymore.
• RAW
  Called "raw" because they are unprocessed, typically coming out of your camera and into an image editor. "RAW" is deceptive because there is not a single "RAW image format." There are many dozens of RAW formats, including Canon RAW and Nikon RAW. This format is helpful because it can contain a wide range of color information, making camera exposure changes more easily accomplished even outside of your camera. This is not as easily done once the RAW file is converted to other formats like JPG or PNG. RAW files are not compressed, making them unhelpful for internet use or emailing to friends; most people will need a special viewer software package to view RAW files.
• DICOM
  Digital Imaging and Communications in Medicine. This is a special format used by the medical community; it can contain patient information along with related images, like X-Ray images. You probably won't see this one unless you work in medicine.