File Format Notes

File Formats

All computer files are saved with a certain format

Format is determined by the origin of the file.

EX: Photoshop has .psd

Graphic Files (like photo or video) can be reduced in file size by compression.


Lossy VS Lossless

Graphic image formats have two categories of compression: Lossy and Lossless

Lossy: Image data is “lost” or reduced and can cause poor image quality. Results in “Compression artifacts”

Lossless retains image data for higher quality but larger file size.

Some  Lossless formats are better for bigger files, like .tiff or .png or .pdf, but are not always web friendly

Lossy can result in pixelization.

Graphic Formats

TIF, JPG, and GIF are the 3 most common formats for common activities such as printing, scanning and displaying images over the Internet.

TIF is better for printing, JPEG has smaller file sizes, and GIF can have animated files and alpha channels.

PNG is a common web format and is high quality and can contain an alpha (transparency) channel

Alpha Channel: Does not need a square border, can be a cutout.

Each format has its own advantages

TIF

TIF: Tag Image Format. Common for desktop publishing, print, photo and graphic design.

A LOSSLESS file format.  Retains image fata for maximum image quality.

Can result in larger file sizes. Not fit for internet or browser usage.

JPEG/JPG

JPEG: Joint Photographers Expert Group

Created for digital photography

LOSSY format: compresses images.

Can reduce images 10:1 without showing significant compression artifacts

Compression level is adjustable

Recompressing images makes them look worse every time. Work in native format if possible.

Worst choice for graphics.


GIF


GIF: Graphical Interchange Format

Is best for graphics or images that have flat color or flat tone.

“Indexes” color and reduces image size.

Color channels can be changed from 1 to 8

Contains no DPI (Dots Per Inch) data for printing

GIFS can be animated and made into “Cinemagraphs.”

Worst choice for photographs.

Know Your Pixels

TIF and JPG are best for images with pixels that blend in color, these are called “contiguous pixels”

GIF is best for images with flat, even tone or “non-contiguous pixels”

Alias vs Anti-Alias

Aliased have hard edged pixel art.

Anti-Aliased: smoothens out shapes with gradients.­