On Mon, May 07, 2001 at 07:54:03PM +0000, John A. Lind wrote:
> At 00:02 5/8/01, Joel Wilcox wrote:
>
> >Wow. Thanks.
>
> You're welcome. Researched some of this stuff for a tutorial on my web
> site about lenses. Not yet complete, but getting there.
>
> >I've got the Viv tubes. I'm not thinking about using the 135/2.8 on the
> >notion that it would be faster but because the lens seems to me to be very
> >good. Also, all being otherwise equal between the two, if the 135/4.5
> >allowed me to stay further away from the subject, I would find this to be
> >a selling point. I don't do well stalking butterflies even with the 90/2.
>
> Jumping to the 135/2.8 with extensions will require a steadier hold
> compared to the 90/2 if you're doing this hand held. Should be lighter
> than using the 90/2, although heavier than an 85/2 with tubes.
>
> >I've had some good experience using the 300/4.5 with a little extension
> >for close focus at a good working distance, but not handheld.
>
> I've used the 200/4 Zuiko with extensions also, although not as often as
> the 85/2 and 135/2.8 lenses. As focal length is increased to gain distance
> from subject, the length of extension tube required for the same
> magnification is likewise increased.
>
> Thinking out loud:
> I ought to put together a table showing what the various combinations tube
> lengths do with various Zuiko prime lenses; both with Oly tubes and the
> Vivitar. Found the longest tube out of the Vivitar set, the 36mm, quite
> handy with the longer lenses. Wouldn't be hard to do in a
> spreadsheet. Results would be approximate measuring from lens exterior as
> the theoretical formulae are based on distances from lens principal points
> (nodes) and film plane. Might be useful for some as the TOPE 6 window is
> still open (have you done yours yet?).
While working with my spreadsheed, it occours more questions than answers.
The real focus lenght might differ about +/- 5%.
And a lens isn`t a ideal thin lens. When you calculate macro-distances this
diffrences values matters.
As theoretical ideal 135mm my spreadsheed gives the following values :
Auto-Macro-Tubus max. extension (58mm):
Distance to film: 64.2 cm
working distance: 42.4 cm
lenght of equipment 22.0 cm
Now I´ve made some measurements:
For the 135mm /F 4.5 Macro I've meassued the following:
Auto-Macro-Tubus max. extension (58mm):
Distance to film: 61.0 cm
working distance: 39.2cm
lenght of equipment 22.0 cm
with additional extension tubes 7,14,and 25 (105mm):
Distance to film: 53.6 cm
working distance: 27.0cm
lenght of equipment 26.7 cm
Though the 135mm isn`t a thin lens, this values are hard to guess.
The best guess is 126mm real focal lenght and 26mm distance between priciple
planes
(dt. Hauptebenenabstand?).
Does somebody know the real values?
Frieder Faig
>
> -- John
>
>
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