OK. For a zoom lens there are usually 2 Aperture readngs available on the lens right? Like the following
According to what I know, this means the max aperture I can get at 28MM is f2.8 and at 105MM is f4. However, what I do not know is whether I have to switch the aperture physically to f4 when I am using 105MM or will it automatically 'convert' the f2.8 to f4??
Thank you for bearing with such a stupid question.