Thanks for the very lucid explanation. So a 90mm f2.0 Zuiko which goes to 1:2
has 45mm extension (45mm/90mm), with a 25mm extension tube its go to 1:1.3
(45mm+25mm/90mm), and with a 65-116 variable extension tube, it goes from
1.2:1 (65mm+45mm/90mm) to 1.8:1 (116mm+45mm/90mm). Now, how do I figure out
the magnification ratios for the regular lenses from 135mm up. The sales info
only give close focusing distances?
Jason E Miller wrote:
> I only read the digests so I hope no one has answered this already...
> One plus of having instant message delivery (e.g. with eGroups) is that
> people could tell if someone else has already responded to a question
> so there won't be 15 identical answers. Anyway...
>
> I've got the 65-200mm, a 25mm extension tube and the 65-116 tube. I've
> used them together a few times and had good results. You can calculate
> the magnifications without actually trying it out though. The magni-
> fication factor for a lens is just the total amount of extension divided
> by the focal length. For example, the helicoid in the 50mm f/3.5 provides
> up to 25mm of extension allowing it to go to 1:2. That's why adding the
> 25mm tube takes it to 1:1 ( (25mm built-in + 25mm tube)/50mm ). However,
> the minimum magnification is now 1:2 ( (0mm built-in + 25mm tube)/50mm ).
>
> The 65-200mm goes to 1:3 by itself (only at the 200mm length), meaning
> that the lens itself can provide up to 67mm worth of extension. Now you
> can calculate the magnification factors available:
>
> 65-200 (at 200) w/ 25mm tube:
> Min: 25/200 => 1:8
> Max: (67+25)/200 => 1:2.17
>
> 65-200 (at 200) w/ variable tube:
> Min: 65/200 => 1:3.1
> Max: (67+116)/200 => 1:1.1
>
> This is all based on formulas but a quick check with my equipment (look
> at a ruler through the viewfinder) shows that these are all approximately
> correct. In fact, I'd trust the formula since I'm using an OM-10 with
> a stupid 93% viewfinder. The 65-200mm behaves a little oddly at the 65mm
> end though. I can't really explain it, but turning the focus ring with
> the variable tube on does not significantly change the magnification. If
> anything, it decreases the magnification. Weird. My best guess is that
> it doesn't truly stay at 65mm. Just a guess though. Anyway, empirically,
> it pretty much behaves as if the lens has no built-in extension at 65mm.
> Thus, we get:
>
> 65-200 (at 65) w/ variable tube:
> Min: 65/65 => 1:1
> Max: 116/65 => 1.78:1
>
> Jason "new to the list" Miller
>
> >Has anyone had any experience using either a 65-200mm or 200mm lens
> >and either the fixed extension tubes or the 65-116 variable extension
> >tube for close-ups. Can someone tell me what the magnification range
> >would be with these various options?
>
> < This message was delivered via the Olympus Mailing List >
> < For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
> < Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|