Quote:
Originally Posted by ab1963
Nikon Nav SW’s 7,10 and 14mm
I have the full set but they are my 3 favourites
|
You like the 40% rule: "Magnifications should be 40% apart".
That is 14/10/7mm.
Extend it both ways, and you have 5mm and 3.5mm on the short end,
and 20mm on the long end (you can see Pentax had reasons for those focal lengths).
Pentax is following that rule with their new 85° XWs: 23mm and 16.5mm are 40% apart. If they continue with the line, the next shorter focal length should be 11.5-12mm.
The Baader Morpheus range follows the same rule:
17.5/12.5/9/6.5/4.5 with the 14mm the "odd man out"
[Originally, 14mm was the longest focal length they could make with the design, but a redesign of the internals allowed a 17.5mm to be made]
I won't argue that the 40% rule always works, but it is a bit more rational than having a focal length every one or 2mm.