I don't know. You get some really weird things at the macro level.
The simple thing to do is to buy an FA style macro lense. Most of those
have built in helicoids to 1:1 (exception is the FA 100mm f3.5).
With these you only need focus and shoot---although I wind up turning the
auto focus off and focusing by moving my head (and camera) back and forth.
If you are using the older 1:2 macro lenses then you will need a set of tubes
to get to 1:1 (all three tubes) around 60mm of additional extension will get
a 100 mm macro lense to 1:1. I am not sure whether you must add the helicoid
extension additionally.
the 50 mm lense needs much less extension to get to 1:1 but it is pretty clear
that these functions are not linear.
There are lots of things to photograph without pushing the 1:1 envelope
much andI am trying to master that before considering jumping much beyond where
you really begin to hit the wall of exposure problems.
"Peifer, William [OCDUS]" wrote:
> Hi all,
>
> This has been an interesting thread regarding extension tubes, etc. My
> question is this: Can you get good estimates for expected magnification,
> extension tube length, and so forth from simple optics calculations? By
> simple, I mean REALLY simple:
> 1/d(o) + 1/d(i) = 1/f ; and
> "Do or die equals suicide" [ A little bizzare, but an old mnemonic for
> remembering d(o)/d(i) = s(o)/s(i). ]
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