PCA Cala wrote:
> Hello Francis:
>
> << i was interested in getting the auto macro tube 65-116 but have been unsure
> as to which head lens to get. >>
>
> There are 4: the 20, 38, 80, and 135 mm. Which one depends on the
> magnification ratio you are intending to photograph at. You didn't state any.
>
> << i was wondering how the 50 3.5 or 2.0macro lenses work with this or even
> the 90 2.0. >>
>
> They aren't intended for it's use. It's too long at it's shortest reach. For
> example, a 25 mm extension tube takes the 50 mm from 1:2 to 1:1
>
> << what types of magnifications do i get and what is the resolution compared
> with the the more dedicated hear lenses. do you know a good source of
> information for this? >>
>
> The range of magnifications for the three lenses are as follows:
>
> 20 mm = 6.8:1 to 9.5:1
> 38 mm = 3.1:1 to 4.5:1
> 80 mm = 1:2 to 1.2:1 [to 2:1 with Close-Up Lens 80 mm]
> 135 mm = infinity to 1:2.3
>
> Obviously there are gaps here, which would be narrowed with the bellows rather
> than the Telescoping Extension Tube. (I seem to recall small gaps even with
> the bellows.) My info is from the out of print "The OM System Lens Handbook"
> although there are other sources.
>
> As far as lens tests, I don't ever recall any. But knowing the compromises
> needed in producing macro lenses - which most manufactures have ignored - it
> holds that these four lenses are optically more efficient than what might seem
> like more versatile designs from other manufacturers. In another words, I'm
> confident that they can't make them much better than these! (The 80 mm seems
> flawless to me. The 135 mm isn't acceptable to me at infinity, but it was
> designed for optimum performance at 1:5 and does great in macro.) Plus, one
> is hard pressed to find 35 mm optics that go greater in life size than 1:1
> The 38 and 20 mm *auto* lenses were Olympus exclusives.
>
> Gary Reese
> Las Vegas, NV
Gary,
I don't think I was ever able to thank you for this explanation. It has come in
handy. Still looking around for a macro lens. I was looking at the chart that
comes in the manual and it shows that the 90mm/2.0 and the 135mm/4.5
autoextension
tube 65-116 combination get the same magnification, actually the 90/2.0 has a
slight edge. Is it right for me to assume that the difference is the maximum
distance from which they can get this magnification? I plan to take macro shots
for medical purposes so distance is not an issue with me. I may at some time in
the future use it for nature shots. I may have some future use for 1:1
reproduction, and looking at the chart the so I guess the 80 mm macro is the
best
for this application unless i use the 90mm with a extension tube. Which do you
think is the better combination?
thanks again
>
>
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