At 03:08 6/9/99 , Warren wrote:
>The 7, 14, and 25 extension tubles will provide continuous focus using all
>combinations from 0.1X to 1.0X with Zuiko 50/1.8, 1.4 and 1.2 lens.. The
>Vivitar tubes will cause some gaps in the magnification range (I think). With
>the 25mm extenstion tube the 50/3.5 will go to 1:1 even though the 80/4 is
>recommended at this magnification.
>
>I don't think you'll miss the gaps between the various extension tubes at all
>as the gaps should be quite small.
>
>Warren
Thanks for the response on this. Between your reply and a search of the
archives (which maybe I should have done first) I think I sorted it all
out. :-)
The explanation I found there stated the Zuiko 50mm standard lenses rack
their focus 7mm throughout the entire focus range which is why there are no
gaps with the Oly tubes if you add its 0-7mm focusing rack.
Did some math based on the chart for the Oly tubes with the Zuiko 50mm
lenses as an example. If some other focal length lens (Zuiko or 3rd Party)
racks out 12mm or more in its focus the gaps using the Vivitar tubes
disappear also. If that lens would happen to be an 80mm and racked 12mm or
more on its focus, it would behave with the Vivitar tubes (no gaps and
achieve 1:1) just as the Zuiko 50mm lenses do with the Oly tubes.
For my purposes . . . which do not include metrics (photos with precisely
magnified images) . . . you are right in that the gaps are not significant.
Then again, simply adding an Oly 7mm auto tube to the stack would
completely fill in the gaps for a lens that racks its focus less than 12mm.
Thanks,
-- John
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