kye Posted August 17, 2020 Share Posted August 17, 2020 1 minute ago, noone said: Not sure I get that. F stop is a ratio and a constant aperture zoom has a constant ratio (IE 2.8 at 24 and 2. at 60 for your Sigma). The physical size of the lens will be determined by the largest focal length if it is constant aperture. I think what @Enjay is saying is that when you design a zoom it's maximum aperture will always be larger on the wide end, so in order to make a constant aperture zoom they just design it so that it closes down at the wide end to match the maximum aperture of the long end. In this sense, if you had a variable aperture zoom, say an 18-55mm f3.5-5.6, then you could just set it to f5.6 and then zoom in and out and you'd have the benefits of a constant aperture, as well as being able to open up wider than f5.6 in the middle and at the wider end. Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.