Printing technology has come a looooong way over the past 2 or 3 decades: today, you can get photo quality prints mass produced on your own home printer. Compare this to the type of effort needed to make media like coloured comic books just a few years ago and one realises just what an achievement it is.
The ImageView website is an attempt to discuss digital images, the technology underpinning their production, and file formats in an accessible, non-technical way. It is perhaps to be thought of as a “digital images for beginners” guide. It is hoped that the information contained in the following pages is a succinct description of some of the basics pertaining to digital images, specifically addressing their different file formats (in broad categorisation) and the appropriate uses for each.
The current page will look at a few file formats of the “raster” variety (see the link above for a more detailed description of raster files) that are the most commonly used image file formats; the page will simultaneously, if briefly, look at which formats are the most internet friendly, as many readers will want to upload images onto various social-networking or blog platforms.
BMP (Windows bitmap)
- This file offers a high quality image, and if you have enough space on your personal hard drive, it is often advisable to save original images in this format. It is, however, the largest bitmap format (see the “raster” link) as it is uncompressed and is a “lossless” format. Lossless means that no detail is lost when saving an image as a BMP file.
JPEG (Joint Photographic Experts Group)
- The JPEG (or JPG in DOS) is a versatile and much used format. It does, however, along with its advantages have some disadvantages. JPEG is a “lossy” format, which means that some detail is lost whenever an image is saved as a JPEG file. This is because JPEGs compress image files in order to make them smaller, portable, internet friendly and usable on cell phones. The loss of image quality often results in “artifacts” which are blemishes caused by the file’s algorithm: essentially, in the compression process the sharp divergences of contrast are made more gradual. In practice, too much compression results in colours “leaking” into one another, causing disturbances around sharply contrasting elements in an image. Many image editing programmes allow the user to control the level of compression when converting to JPEG: the trick is to balance the down-scaling of the image memory size with the quality needed for the image’s purpose. Artifacts, however, are much less common in photo-type images, which is what JPEGs are designed to handle. Another thing to bear in mind is that all internet browsers can read JPEG files.
GIF (Graphics Interchange Format)
- GIF files are restricted to using only 256 colours, and are therefore great for images which do not require subtle colour variations: for example, diagrams, logos, shapes and monochrome cartoon type drawings. GIF is also widely used for animation. The files are small (owing to the fact that they are a “lossy” format), easily downloadable, and widely supported by internet browsers.
PNG (Portable Network Graphics)
- The PNG file is an open source variation of the GIF file. It does have some advantages over its predecessor: the GIF file only allows for 256 colours whereas the PNG can support 16 million colours. The file is best used, however, in images with large planes of consistent colours. In general, the PNG file can effectively be used, as it is a lossless format, for the editing of pictures and other images; once the edit is complete, a JPEG would be the most appropriate format for picture distribution/ internet uploading. Most contemporary browsers support the PNG file, and with the JPEG and GIF, forms one of the three best files for internet usage.
TIFF/TIF (Tagged Image File Format)
- The TIFF format file has a wide possible range of colours as it can save 8- or 16-bits per layer of light spectrum primary colour (red, green and blue [RGB]), which means it can have up to 48-bits of data per pixel. TIFF formats can be either lossy or lossless, and are a very popular format in the photography and printing industries. The file is, however, not well supported by internet browsers.
This information can be seen to pertain to specific formats, and relates the strengths and weaknesses of each type of “raster” file. The other pages on the site offer a more detailed description of the workings of the different file types, which should make the above information much clearer if some aspects of it are still somewhat vague. The advantage to knowing about the different image formats is that you can make better decisions with regards to what type of format is best suited to sharing and storage: in a way, knowing the above information is like comparing tablet prices before making a purchase – that is, facts empower you with knowledge.