On 2/9/2023 1:33 PM, Mike Gordon via olympus wrote:
Frank writes:
<<<Actually, the Sigma 180mm 2.8 macro is also effective 115mm at 1:1
<<<If I may believe the formula I found some time ago ;-).
Wow, more than I would anticipate!
Basically all modern macro lenses indeed do drop focal length when they go to 1:1 but the
working distance still much better with the longer FL at lower mag. The "effective
focal length" calculations are very very approximate with a complex lens,
but give some estimate of the degree of FL shortening. My CV 180/4 in OM
mount goes to 1:4 and does well on extension with good working distance as the
FL shortening is much more modest--typical for primes.
Canon 100 f/2.8L - drops to 75mm
Nikon 105 f/2.8 G VR - drops to 78.5mm (25% drop)
Sony 90 f/2.8 G - drops to 70mm (22% drop)
Leica R 100 f/2.8 APO - drops to 75mm with elpro 1:1 adapter (no drop at 1:2)
Voigtlander 125 f/2.5 APO - drops to 95mm (24% drop)
Voigtlander 110 f/2.5 APO - drops to 87.5 (20% drop)
An interesting intellectual exercise, but what's the point? Frank's spreadsheet tells me the FL of my 60/2.8 is 48 mm @
1:1. How do I use that? What practical purpose might it serve?
I only want to know the magnification and the working distance. (1:1, 1x, and
83 mm.)
It's like the Oly 12-100/4 and the PLeica 12-60/28-4. Both have the same max mag., but on the Oly it's at 12 mm, and
highly compromised by short working distance for actual use. The PLeica is at 60 mm and quite useful. (There's also a
perspective difference.)
Empiricist Moose
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What if the Hokey Pokey *IS* what it's all about?
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