Re: macro questions @i3g2000cwc.googlegroups.com:
I'll agree with Jeremy's reply, up to a point ;-)
And that point is, right where he says, "forget about reversing
rings, extension tubes, using normal lenses attached to bellows or using
those close-up screw-on adapters".
All of them have their place, and many may be used in combination
with one another. It all depends on what you're photographing and how
close you want to get. Yesterday I was propped on a table on a dock,
shooting with a 105mm macro lens on both a 2X teleconverter and a 36mm
extension tube. Why? Because that's what it took to get my subject as big
as I wanted. (I was also switching back and forth between a flat-panel
slave strobe and a macro attachment for a standard flash unit...)
(True) macros are typically the sharpest lens in any manufacturer's
lineup, optimized for detail work, and usually pretty fast (wide maximum
aperture, often f2.8). This allows you to see and focus on subjects in
less-than-optimum lighting conditions. Other options often have their own
foibles - light falloff for extension tubes and bellows, edge distortion
from closeup diopters (screw-on magnifiers), and so on.
So, your specific questions:
Macro photography is usually defined as achieving a magnification
of at least 1:2, but more often 1:1. This is the comparison of your
subject size to the size it appears on the film plane - change the colon
to a slash to make a fraction and you're closer to the mark: 1/2 lifesize
to 1/1, or full lifesize. Which means a coin, laid alongside the slide or
negative image of itself, will be the same size at 1:1. And of course,
the slide/negative image will be half the size of the real coin at 1:2.
Lots of argument about "true macro" photography, but you can
generally stick with the idea of "really close up photos" and be fine.
As Jeremy indicates, a telephoto lens usually won't focus close
enough to mimic a macro lens - you're often talking a magnification of
1:4, 1:6, along those lines. Extension tubes, which allow lenses to focus
closer than their design, can change this, but there's often a tradeoff.
First, they lose some of the light that the lens transmits - it simply
falls outside the film area or bounces off the tube walls. Second, not
all lenses can measure up to the additional magnification, and you find
out that they get noticeably softer when used with tubes. And finally,
your magnification depends on the focal length of the lens and the amount
of extension - the longer the lens, the more extension you need to
increase the magnification, and thus less light comes through. Not to
mention starting to make a really awkward thing hanging off the front of
your camera ;-)
What kind of subjects? Aw, c'mon, whatever you want to shoot! Bugs
and flowers are typical, and also done to death (not that that stops me,
but...). I've also done macro aquatic subjects with a fishtank, and
fossils. Reptiles, feather details, frost, seed pods, and tiny
footprints. Go wild. The details typically missed by the naked eye are
what most people want to reveal. But maybe you're not most people... ;-)
Hope this helps. It's not a simple field, and there's tons of
approaches and techniques. Poke around, and good luck!
- Al.
--
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Online photo gallery at www.wading-in.net
Al Denelsbeck
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