Depth of field question

Started Dec 22, 2012 | Discussions thread
Leonard Shepherd
Veteran MemberPosts: 8,918Gear list
Re: To help clarify
In reply to Leon Obers, Dec 26, 2012

Leon Obers wrote:

It is already by optical formulas that by enlargement the effective aperture shall be more small.When focal length is not changing, enlargement of 1:1 the effective aperture shall be 2 stops more small than at infinity. So a f2.8 lens shall be effective f5.6 of the focal length at this enlargement by today's Micro Nikkors, the effective aperture opening shall be less small than f5,6shorteningBy the

To help clarify a theoretical 105mm lens of symmetrical design at 1:1 focus has the angle of view of a 210mm lens at infinity focus; and transmits two stops less lights than when focused at infinity.

The Nikon 105mm f2.8 macro D is not symmetrical at 1:1, and changes to an equivalent 78.5mm f2.1. It transmits only one stop less light compared to 2 stops less with a theoretical symmetrical lens.

-- hide signature --

Leonard Shepherd
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.

 Leonard Shepherd's gear list:Leonard Shepherd's gear list
Nikon D800 Nikon D7100 Nikon AF-S DX Nikkor 18-200mm f/3.5-5.6G IF-ED VR Nikon AF-S DX Nikkor 12-24mm f/4G ED-IF Nikon AF-S Nikkor 16-35mm f/4G ED VR +19 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