1: Positioning and subject matter
The first consideration when embarking on a megapixel project is to look at edge design fundamentals, such as effective camera positioning and appropriate model selection. A common initial design concept is to use a single megapixel camera to replace several high-resolution analogue or IP cameras. Increasingly though, there is a demand for more targeted megapixel images, concentrating on predefined areas of interest. The reason for this seems to be a thirst from clients for better definition, evidential quality images.
2: Lens selection
This has always been an essential design element, but never more so than with megapixel cameras. Lens manufacturers such as Tamron have designed improved aspherical lenses specifically for megapixel applications. Matching a megapixel lens with a megapixel camera will provide tangible benefits in terms of picture quality, as the lens is shaped especially for use with megapixel chip sets to improve resolution, sharpness, and colour depth/reproduction. You should still consider the required focal length, f-stop, field of view and object distance. The key difference, however, is in the manufacturing process, so always look to use a megapixel lens with a megapixel camera, in spite of increased cost.
3: Size
The number of megapixels used should always be application-specific, but light levels are also a crucial factor. There are several camera models on the market which offer dual capture, where separate colour and monochrome chip sets are combined within a single unit. This is a very effective approach in low light applications, and often occupies a single stream on the recording platform as the image fluctuates between sensors based on light levels. Effective noise reduction is crucial for external applications. This will have a significant impact on the file size, bandwidth and storage. The higher the pixel count, the worse the low light performance tends to be. This is simply because the individual pixels are made smaller to fit a standard chip size. A general rule of thumb for low light applications is to use cameras rated between 1 and 2 megapixels.
4: Set Up/Configuration
The great thing about megapixel cameras is that they allow real flexibility when it comes to configuration. Most offer the ability to select a variety of compression formats and these often include H.264 which has revolutionised the implementation of megapixel cameras. Megapixel cameras are now streaming at a similar rate to standard MJPEG or MPEG4 IP cameras, facilitating a significant reduction in transmission and storage costs. In many cases, a 90 per cent saving can be achieved over MJPEG and JPEG 2000 versions. The installer can set the camera to full resolution or choose to crop the image at source to exclude irrelevant areas of the scene. The result is a high definition ‘window’ within the image which will reduce bandwidth and storage requirements further.
5: Head end recorder
Having carefully considered the selection and configuration of any megapixel camera, it is essential to reproduce the resulting high definition images in the most effective way. A major consideration must be support for the recording of H.264 streams. Additionally, the recording software selected should offer deep integration with the camera to enable as much centralised configuration as possible. After all, operational parameters are often adjusted some time after installation. The software should indicate local camera alarm status including any edge analytics offered by the camera.
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