Aperture/focusing distance changes at different FL for zoom lenses?

Started Mar 21, 2013 | Discussions thread
Ulric
Senior MemberPosts: 2,613Gear list
Like?
Re: Aperture/focusing distance changes at different FL for zoom lenses?
In reply to pavinder, Mar 21, 2013
It's not that the aperture closes down, but that the focal length increases.

Of course the aperture closes down! As the focal length increases, the aperture closes.

That's what it means when the number goes from 3.5 to 4 to 5.6 etc!

Remember that the f-number is the ratio of the focal length to the entrance pupil. Take for example the very nice M.Zuiko 40-150 mm zoom. At 40 mm, its relative aperture is 4.0 => 40/4.0 = 10 mm. At 150 mm, its relative aperture is 5.6 => 150/5.6 = 27 mm. No closing down there.

 Ulric's gear list:Ulric's gear list
Panasonic Lumix DMC-GF3 Olympus OM-D E-M5 Panasonic Lumix DMC-GM1 Panasonic Lumix G 20mm F1.7 ASPH Panasonic Lumix G 14mm F2.5 ASPH +6 more
Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow