From: fiddler@concertina.Eng.Sun.COM (steve hix)
Newsgroups: rec.photo
Subject: Re: Getting close without a macro lens (ext. tubes, closeup diopters, etc)
Date: 15 Sep 1992 23:42:40 GMT
Organization: Sun Microsystems, Mt. View, Ca.
NNTP-Posting-Host: concertina

In article <195ak6INNr1l@almaak.usc.edu> ajayshah@almaak.usc.edu (Ajay Shah) writes:
>I was fishing for ways to get get better wild-flower pictures without
>buying a Macro lens.

Careful...sometimes you get what you pay for, other times you get less than what
you pay for.

>Have you used extension tubes?  How well do they work?  I believe they
>are highly recommended for good optics (because they really do
>nothing to the light).

With the right lens, extension tubes can be quite nifty...with the wrong
lens, they're not so.  One thing you *will* notice is that adding extension
makes the image darker (your lenses aperture stays the same, the focal
length in use increases: your effective f-stop goes down quickly).  In
these days of TTL metering, it's not so much of a problem, but it forces
you to slower and slower shutter speeds...which means image/camera movement
is more of a problem.  Most macro lenses (other than those that offer
internal focusing) do exactly the same thing, but they're more convenient
to use, and you won't lose metering or AF, assuming the lens offers it.

Oh yeah, at any given aperture, depth of field decreases as you focus
closer.  At 1:1, it's *really* shallow.

But the lens you use them with does something with the light.  And that
may leave you in trouble.

Most macro lenses focus closer by (just like the extension tubes) moving
the lens away from the film plane.  The problem is, the lens you have
now is probably optimized for something between 1:10 and infinity focus.

You might well be able to focus down to 1:2 or 1:1 with the extension
rings, but the image might well be so badly degraded by that point that
it's not worth doing.

Macro lenses are designed to still produce sharp images down into the
macro range.  Most of them are also good normal lenses, just a bit slow.

>The Nikon salesperson recommended "closeup diopters" using which I
>could go closer, and retain AF and auto exposure modes.  He said there
>are three options: 0 (#2732), 1 (#2733) and 2 (#2734) diopters.

Nikon also makes a series of two-element diopter lenses, which work
pretty well.  Probably better than the single-element diopter lenses
that these appear to be.  (You can stack diopter lenses to get even
closer, but image quality degrades further.)

If you're not going to be getting *real* close, they might work
pretty well.  A "real" macro lens will probably give you better results,
but the diopters or extension tubes might give you "good enough"
results.

>What are these gizmos?  How do they work, and how well?  How much do they
>cost?  I didn't see them listed in the back pages of popular photography.
>
>Adorama also lists a lot of other toys under "close up accessories"
>with numbers like PB-6, BR-4, PN-11, PC-3, etc.  What are these?

Go talk to your Nikon dealer... (they're a bunch of different things,
extension tubes, bellows, etc.)

A good introduction to macro lenses, extension tubes, diopter lenses,
and so on is found in John Shaw's book on closeup photography in nature.
Most good-sized camera stores with a good book section should have it.

I think reading that would answer your questions, and you'd know which
tool was appropriate for what circumstances, and even better, you'd
know what quality of results you could expect.

--
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Of making many books there is no end...  |  What's wrong with chasing 
                       -- Eccl. 12:12    |  nebulae till 3 am?  |-(
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