ong-focus lens
长焦距透镜、长焦镜头
例句：
1.
I didn't have to set the focus as I had a wide-angle lens; I knew, so long as I had the right exposure, the depth of field was enough.
我无需调整焦距，因为我用的是广角镜头；我知道，只要使用正确的曝光组合，便能得到足够的景深。
2.
Firstly, a telescope system is made up with a concave lens and a long-focus convex lens, by which the angle of the parallel beam from the collimator can be change.
该方法借助一个焦距较长的凸透镜与被测凹透镜组成无焦系统，可以使准直管出射光束的张角发生改变；