在35mm单反照相机自动对焦已成为当今主流时，为何迟迟没有推出自动对焦的中画幅单反相机呢？通常说法是：需求有限使得生产中画幅单反相机自动聚焦系统成本过高；较大尺寸的镜头使得实现快速、精确自动对焦比较困难；中画幅相机具有易于对焦视景屏幕，没有必要采用自动对焦； 35mm SLR camera autofocus has become the mainstream nowadays, why delay the introduction of autofocus medium format SLR camera it? The usual argument is: the limited demand makes the production of frame SLR camera autofocus system cost is too high; larger size of the lens makes it fast and accurate autofocus more difficult; medium format camera has easy to focus screen, there is no need to use autofocus;