Image File Formats

O L I V E R KA P L A N

IMAGE FILE FORMATS

RAW (UNPROCESSED CAMERA IMAGE CAPTURING DATA)

• A camera raw image file contains minimally processed data from the image sensor of a digital camera. Raw files are named so because they are not yet processed and therefore are not ready to be printed or edited. Normally, the image is processed by a raw converter where precise adjustments can be made before conversion to a file format such as a TIFF or JPEG for storage, printing, or further manipulation. There are hundreds, of raw formats in use by different models of digital equipment.

PROS• Format can be used by many applications.• File size may be smaller than TIFF. • Saved at the camera’s maximum colour bit depth.

CONS• Large file size means that it can take longer to save an image to the memory card,

i.e. less images captured per second.• Difficult to work with images because they need to be converted to something else

(like TIFF) before they can be shared and manipulated.

BITMAP/RASTER GRAPHICS• Raster graphics, also called bitmap graphics, are digital images that are

composed of tiny rectangular pixels. They are arranged in a grid or raster of x and y coordinates in such a way that it forms an image. It is also referred to as bitmap since it has information that is mapped directly to the display’s grid.

• The file size of a raster image depends also on the size of the image, which is determined by the number of pixels being used in the image. This means that an image with a 1280x720 resolution will contain 921,600 pixels while a full HD 1920x1080 image will have 2,073,600 pixels.

• Some examples of Raster Graphic File Formats are as follows:

JPEG (JOINT PHOTOGRAPHIC EXPERTS GROUP)

• A JPEG is an image file format used for compressing image files. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality.

PROS• Retains up to 16,000,000 colours.• Suitable for images, high details & quality pictures.• It is the most used graphic file format.• Approved as standard in 1994.

CONS• It does not support transparency.• File size larger than GIF because of colour information.

GIF (GRAPHICS INTERCHANGE FORMAT)

• A GIF is a lossless file format for image files that supports both animated and static images.

PROS• 256 number of colours.• Uses lossless compression.• Support for transparency.• Small file format.

CONS• The oldest format for web – 1989.• In most cases it has a bigger file size than PNG.• Loss of colour variation.

PNG (PORTABLE NETWORK GRAPHICS)

• Portable Network Graphics (PNG) is a raster graphics file format that supports lossless data compression. PNG was created as an improved replacement for GIF files and is the most widely used lossless image compression format on the internet.

PROS• 256 number of colours.• Uses lossless compression.• Suitable for flat areas of colours, logos, transparent or semitransparent images• In most cases has a smaller file size than GIF• It has alpha channel transparency which is more advanced than GIF’s

transparency.

CONS• Relatively large file format.• In different situations it has bigger file sizes than JPG.

TIFF (TAGGED IMAGE FILE FORMAT)

• Tagged Image File Format (TIFF) is a computer file format for storing raster images, popular among the publishing industry and photographers. The TIFF format is widely supported by image manipulation applications and publishing and page layout applications.

PROS• No image data is lost. • Better image quality than even the JPEG fine quality.• Good for images that will be heavily manipulated in a photo editing program.

CONS• File size is very large.• Still need to make sure that exposure, white balance and colour saturation are

properly set because fixing these in the photo editing program will degrade the image to a certain degree.

VECTOR GRAPHICS

• Unlike other formats, vector graphics are not made up of a grid of pixels. Instead, they are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, square, triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams.

• Some examples of popular vector graphic file formats are as follows:

AI (ADOBE ILLUSTRATOR ARTWORK)

• Adobe Illustrator Artwork (AI) is a file format developed by Adobe Systems for representing single-page vector-based drawings in either the EPS or PDF formats. The .ai filename extension is used by Adobe Illustrator.

PROS• No loss of image quality.• Can be scaled to any size.

CONS• Not as portable as EPS files.

PSD (PHOTOSHOP DOCUMENT)• A PSD file is a layered image file used in Adobe Photoshop. It is the

default format that Photoshop uses for saving data. PSD is a proprietary file that allows the user to work with the images’ individual layers even after the file has been saved. When an image is complete, Photoshop allows the user to flatten the layers and convert the flat image into a JPG, TIFF, PNG or other file format so it can be shared.

PROS• Allows user to change images with good control over individual layers, channels

and paths.

CONS• Only works in certain applications/software programs.• Not useful for web display.

PDF (PORTABLE DOCUMENT FORMAT)• The Portable Document Format (PDF) is a file format used to present

documents in a manner independent of application software and hardware. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics and other information needed to display it.

PROS• PDF can be opened on any device with any operating system in exactly the same

form in which it was created.• Easy for viewing• Takes up very little storage space.

CONS• It’s not free to edit PDF files.• It is difficult to work with text in PDF files because they are perceived as pictures.