Properties of Media & Preparing Products for Distribution
Why Properties Matter
Every media file has technical properties that determine its visual or audio quality and its file size. Understanding these properties is essential because file size and quality always exist in tension: higher quality means larger files, and larger files take longer to download, stream or load. A media creator must balance these properties for the specific platform and audience. A print-quality photograph that is perfect in a magazine will be far too large for a web page, where a viewer expects the page to load in under two seconds. Preparing a product for distribution means making deliberate decisions about each technical property to optimise the file for its purpose.
Image Resolution and Dimensions
Resolution describes how much detail an image contains. For print, resolution is measured in dots per inch (DPI): professional print output requires at least 300 DPI, and images printed at lower resolutions appear blurry or pixelated. For screen display (websites, presentations, social media), 72 to 96 pixels per inch (PPI) is sufficient because monitors display fewer pixels per physical inch than a printer lays down ink dots. Sending a 300 DPI image to a website is wasteful — it produces an unnecessarily large file with no visible quality benefit to the viewer.
Dimensions are measured in pixels (width x height). A full-width website banner might need to be 1920 x 1080 pixels, while a social media profile picture might only need to be 400 x 400 pixels. Resizing an image to the exact dimensions required for the platform reduces file size without the need for aggressive compression. As a rule, always reduce image dimensions before uploading to a web platform, rather than relying on the platform to resize the image for you.
Print images require at least 300 DPI (dots per inch) to appear sharp. Screen images require only 72 to 96 PPI (pixels per inch) because monitor displays do not resolve detail as finely as printed ink. Using a 300 DPI image on a website wastes bandwidth without improving the viewer's experience.
Bit Depth and Colour
Bit depth determines how many colours an image can contain. A 1-bit image contains only black and white (2 colours). An 8-bit image can contain 256 colours — enough for simple graphics and GIF animations, but not for photographs. A 24-bit image uses 8 bits per channel across three channels (red, green, blue), giving over 16 million possible colours — this is referred to as true colour and is the standard for photographs and complex digital artwork. A 32-bit image adds an alpha channel for transparency information on top of the 24-bit colour data. Higher bit depth produces better colour accuracy but increases file size.
GIF files are limited to an 8-bit palette of 256 colours. This is why GIFs look flat or banded when used for photographs — the limited palette cannot accurately represent the millions of subtle tones in a photo. GIF is best reserved for simple graphics, text-based animations and logos where only a few colours are needed. PNG supports both 8-bit (PNG-8) and 24-bit (PNG-24) colour. PNG-8 produces smaller files than PNG-24 but with the same 256-colour limit as GIF; PNG-24 supports full true colour and is appropriate for photographs needing transparency. Choosing between PNG-8 and PNG-24 is itself a file size vs quality decision that a creator must make based on the complexity of the image.
Compression: Lossy vs Lossless
Compression is the process of reducing a file's size so it can be stored, transferred or streamed more efficiently. Lossy compression permanently removes data that the human eye or ear is least likely to notice, producing a significantly smaller file at the cost of some quality. JPEG and MP3 are lossy formats. Lossless compression encodes the data more efficiently without discarding anything, so the original can be perfectly reconstructed. PNG, GIF and WAV are lossless. The choice between lossy and lossless depends on the purpose: professional editing and print require lossless quality; web delivery and streaming benefit from the smaller file sizes that lossy compression provides.
Each time a JPEG image is opened, edited and re-saved, another round of lossy compression is applied. The quality loss accumulates with every save, a phenomenon sometimes called generation loss. After several cycles, visible artefacts appear: blocky patterns around edges, smearing in areas of fine detail, and washed-out colours. This is why professional photographers and designers always keep the original high-resolution RAW or TIFF file and export a JPEG only at the very end of the editing process — never editing from the JPEG directly. The same principle applies to audio: always keep the original WAV or uncompressed source file and export the MP3 as the final delivery format.
Bitrate for Audio and Video
Bitrate is the amount of data used per second of audio or video playback, measured in kilobits per second (kbps) or megabits per second (Mbps). For audio, a bitrate of 128 kbps is considered acceptable for casual listening; 320 kbps is considered high quality for MP3. For video, a bitrate of 5 to 8 Mbps is typical for 1080p HD streaming; 4K video may require 35 to 45 Mbps or more. Higher bitrate produces better quality but larger files that require more bandwidth to stream. A video intended for social media upload will be exported at a lower bitrate than the same video destined for a cinema screen or broadcast.
Bitrate directly controls the trade-off between quality and file size for audio and video. Standard MP3 bitrates range from 128 kbps (acceptable quality) to 320 kbps (high quality). Standard video bitrates for web delivery range from 1 Mbps (low quality, small file) to 8 Mbps or more for 1080p HD. Higher bitrate files require faster internet connections to stream without buffering.