[sprandy]

想問問如果支鏡既光圈係f3.5-f5.6，咁係咪無論係部相機度較到幾細(如f22)，最細光圈始終係f5.6呢? 如果支鏡係定f4，係咪即係部相機點較個光圈都只係f4呢??

[simon6158]

f3.5-f5.6 即是說支鏡在最Wide時最大光圈是3.5,最Tele時最大光圈是5.6 .
例如EF-S 18-55mm f3.5-5.6 ,在18mm焦距時最大光圈是3.5 ,在55mm焦距時最大光圈是5.6 .

[Philippe]

除咗呢個數值外,說明書會有講支鏡的最細光圈.當然唔會只有f4或者f5.6咁大.

[yzcat]

Using the same example EF-s 18-55mm f3.5-5.6, you can use
at 18mm: F3.5-22
at 55mm: F5.6-36
at intermediate length: F-stop varies between the limits in the above.

Reference can be made to http://www.canon.com/camera-museum/tech/report/200401/200401.html