为什么闭路电视画面仍然如此垃圾?

The number of CCTV cameras in the UK has been estimated at up to six million, most of which are installed in private homes and businesses. All CCTV cameras – whether the older, analogue type or the more modern, digital ones – have to make trade-offs between picture quality, storage and cost.

据估计，英国有多达600万个闭路电视摄像头，其中大部分安装在私人住宅和企业里。所有的闭路电视摄像机——无论是老式的模拟摄像机还是更现代的数字摄像机——都必须在画面质量、存储空间和成本之间做出权衡。

There are around 13,000 cameras in London Underground stations alone, and the footage from these is kept for two weeks. Upgrading all of these to record at 4K quality instead of 1080p would require an extra 300 million gigabytes of storage, not to mention the cost of the cameras themselves.

仅在伦敦地铁站就有大约13000个摄像头，这些摄像头拍摄的视频被保存了两周。将所有这些设备升级到4K质量，而不是1080p，将需要额外3亿gb的存储空间，更不用说摄像头本身的成本了。

CCTV cameras also generally use wide-angle lenses to cover the broadest possible area. Digitally zooming in on a single person in the distance inevitably results in a blurrier image. Nevertheless, image quality is increasing all the time, and image processing software and machine learning algorithms can now recognise faces even from low-resolution video.

闭路电视摄像机通常也使用广角镜头来覆盖尽可能广泛的区域。数字放大一个人在远处不可避免地导致一个模糊的形象。然而，图像质量一直在提高，图像处理软件和机器学习算法现在甚至可以从低分辨率视频中识别人脸。