Over the last year, there has been an explosion in the number of manufacturers offering megapixel IP cameras, with many reaching over 3-megapixel. However, more recently there have been a number of cameras offering HD-quality video footage in addition to their megapixel cameras.
What’s the difference?
Don’t think of megapixel and HD cameras as being two separate entities. HD cameras are just a special form of megapixel cameras which conforms to certain specifications laid out by the Society of Motion Picture and Television Engineers (SMPTE). The HD specifications must all be met in order for a camera to be classed as an HD camera.
Image sizes
There are two main resolutions for the HD specification, 720p (1280x720, just less than 1 megapixel) and 1080p (1920x1080, 2.1-megapixel). Conventional megapixel cameras often have a number of megapixel resolutions to choose from. Image quality from HD cameras is therefore not as detailed as some other megapixel cameras.
Picture aspect ratios
Similar to the image size, the aspect ratio of HD cameras is 16:9 whereas other megapixel cameras offer a variety of formats such as 4:3.
Frame Rates
This is the biggest advantage to HD cameras over megapixel cameras. Until recently, megapixel cameras have offered very low frame rates compared to low-resolution cameras, sometimes offering as low as 4 frames per second compared to 30 frames per second. This has largely been due to processing power available on IP cameras as well as network restraints.
The HD standard requires footage to be created at 25 or 30 frames per second depending on location, for example, the US runs at 30 frames per second while the UK runs at 25.
Progressive scan
Megapixel camera manufacturers have often used interlaced images to create megapixel footage. This essentially uses two frames to create the image. In the first frame, they capture lines 1, 3, 5, 7 etc with the second frame capturing lines 2, 4, 6 etc. This can be manufactured cheaply but often causes blurred images when fast-moving objects are in view.
The HD standard requires that frames are progressively scanned. This is more expensive but provides a much clearer and crisper image.
Why does the HD format exist?
The HD format was created to try and standardise the video transmissions of megapixel cameras. With HD televisions also conforming to the standard, video output can be made to any HDTV without cropping or resizing.
The HD format has worked well in forcing camera manufacturers to increase processing power and the potential of their IP cameras but conversely, it may also begin to limit the development of megapixel cameras. At present, high-end megapixel cameras can be up to around 8-megapixel. If IP camera manufacturers begin to adopt the HD format for their cameras, the format will need to be updated to include higher and higher resolutions otherwise the extra detail possible at present will be lost.
August 2023 - Note: IP camera technology has blossomed over the last 10 years or so and not only has the resolution increased across the board, but camera capabilities have expanded greatly. The starting resolution is now typically HD 1080p in most cameras except thermal cameras.