NOTES: Understanding File Format

Understanding File Format

File Formats

• All computers docs, or files are packaged in different formats
• The format is determined often buy the files origin, such as a software program like Photoshop, or a device such as a digital camera
• Graphic files such as a photo, video or artwork can be reduced in file size by using image compression formats

Lossy vs, Lossless

• Graphic images under 2 categories on compression, Lossy and Lossless
• With lossy, data is lost or reduced to be a smaller file, but lose resolution, compression artifacts.
• Lossless retains data but larger files

Graphic Formats

• TIF,JPG and GIF are the 3 most common formats. Printing, scanning, ect.
• PNG is a common web format, high rez and can contain alpha (transparency) channel
• Each format has its own advantages and disadvantages

File Format: TIF

• Stands for Tagged Image Format
• Common format for desktop publishing, print, photo and graphic design
• Is a LOSSLESS file format. It retains image data for max quality
• Can result in larger files, not fit to display over images

File Format: JPG

• Stands for Joint Photography Expert Group
• Created for digital photography and works best for photo content
• Is a LOSSY format
• Can reduce an image file size by 10 without showing significant compression.
• The level of compression is adjustable

File Format: GIF

• Stands for graphic Interchange Format
• Id best for graphics or images that have flat color or even tone, such as a cartoon
• Reduces images by “indexing” color from 3 channels to I
• Is adjustable by changing color bit levels from 1 to 8
• COntains no DPI (Dots Per INch) data for printing. Not a proper format for print.

Which Format to Use?

• Photographic images: TIF PNG best quality, GIF worst choice
• Graphics: PNG or TIF best quality, JPG worst choice

Know your Pixels

• Tif and JPG are bests for images with pixels that blend in color, these are called “contiguous pixels” Anti-Aliase
• GIF best for images with flat even tone, or “non-contiguous pixels” Aliase