TIFFs are often used for scanning, editing, printing, or archiving high quality images. EU's Succeed report on formats recommends TIFFs (uncompressed or LZW compression) for the preservation of still images. |
To retain all image quality, TIFFs normally use no compression or LZW or ZIP lossless compression. JPEG lossy compression is rarely used for obvious reasons. LZW is commonly used and works well with 24-bit images, but works poorly with 48-bit images. ZIP is slightly better at compressing images, but is newer and less commonly supported. Both LZW and ZIP compression greatly increase the save time for 24-bit images.
Pixel Order is a TIFF option set to Interleaved or Per Channel (aka Planar). Interleaved is the normal arrangement of pixels from first to last, with each pixel having a red value, green value, and blue value in that order (RGBRGBRGB). Per Channel rearranges the pixels by color channel, starting with all of the red values of all the pixels, followed by all the green values, and ending with all the blue values (RRRGGGBBB). Supposedly, Per Channel helps a little with compression, but is not widely supported.
Byte Order is a TIFF option designed to support the Endianness of the target CPU, either Intel (PC) or Motorola (Mac). Not only should this option be obselete (as both PC and Mac computers use Intel CPUs now), but virtually all modern programs support either Byte Order on any type of computer.
JPEG is a popular format for photographic images on the web because of their small size. To achieve such a small file size, JPEG files use lossy compression. The degree of compression is selectable anywhere in a broad range from low to high. |
A low degree of compression results in a small file size and virtually no noticeable change to image quality. A high degree of results in a much smaller file size and significant loss in image quality. Quality is lost because some image details are permanently discarded to save space. Even more quality is lost due to generation loss, which occurs every time the image is opened, edited, and re-saved.
PNGs are commonly used for a variety of web graphics. PNG files support three main image formats, all of which support transparency: truecolor, grayscale, and palette-based. Lossless compression is used for all three formats to reduce file size while retaining image quality. File sizes are reduced further for images with 256 colors or less by using the palette-based image format. |
PNG8 is an palette-based image, with each pixel being an index to a palette of 24-bit colors. An 8-bit palette-based image is limited to 256 colors, 4-bit to 16 colors, 2-bit to 4 colors, and 1-bit to 2 colors. This format compresses to an incredibly small size while retaining all image detail. The PNG8 format is ideal for icons, logos, and similar graphics because of its very small size and wide support by web browsers.
PNG24 is a truecolor image, and contains three 8-bit color channels that directly specify a color. This format supports millions of colors and retains all image details when compressed. An 8-bit alpha channel can be added for transparency, and the resulting 32-bit RGB+alpha (or RGBA) image format is referred to as either PNG32 or PNG24 with alpha transparency. Additionally, 16-bit color and alpha channels can be used instead of 8-bit channels to support billions of colors. The PNG24 and other truecolor formats are ideal for photographs that must retain all image details when compressed, or when transparency is desired.
|You are done! Time for a break.|
Take a hike. Bring your camera!
The digital one, of course.