長焦距透鏡、長焦鏡頭
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.
我無需調整焦距，因為我用的是廣角鏡頭；我知道，只要使用正確的曝光組合，便能得到足夠的景深。
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.
該方法借助壹個焦距較長的凸透鏡與被測凹透鏡組成無焦系統，可以使準直管出射光束的張角發生改變；