But it might be considered a good way to approach a butterfly on a flower...

Mike.

Canon's 70-200mm F/2.8 IS USM L can focus down to 1.3 meters
(~ 4.3 feet) giving approximately a 1:5 magnifictaion.
(http://www.photozone.de/8Reviews/lenses/canon_70200_28is/index.htm).  

Generally speaking, there are 4 ways to get macroshots (up
to 1:1)

a) a lens with a short minimum focus for it's length usually
  gives you something up to 1:5 or 1:3 (often with dedicated
  "macro" setting).  That practically always means a tele lens
  --- with a wide angle you'd need to be so close at the object
  that you induce serious proportion shifts (WA-portraits give
  wierd noses and ears, this is worse).
  Be aware that zooms and macro-settings on zooms are always
  compromises[0] and that non-macro lenses usually don't have a
  flat field[1], and so on.

b) a lens, probably as in a), and a diopter lens in front.  
  You basically make the lens myoptic, focussing 'infinity'
  at e.g. half or a quarter meter away.
  Pro: Comparatively cheap, small, carryable
  Con: you want an acromatic diopter for better quality, and
       you'll still have to stop down and sometimes fight CAs
       nonetheless.

c) Bellows or fixed-length bellows (aka extension rings) and a
  high quality lens.
  Bellows move the lens exit pupil forwards, so that the
  lens at 'infinity' will focus more closely; the further
  the lens is moved forward, the closer the object has to
  be.
  Pro: Can reuse lenses, comparatively cheap, no extra glass
       involved
  Con: The image is magnified a lot, small lens errors show
       up HUGE, you loose a lot of light (it hits way
       outside the sensor area, after all, you are
       magnifying things here).  Bellows need space and most
       don't transmit any data => stopped down metering,
       stopped down focussing (by moving camera&lens
       forwards/backwards --- this is true for all
       macrophotography).  No focussing to infinity, you
       have to detach the bellows/rings first.  With rings,
       you need to change them according to lens and
       magnification.

d) a true macro lens.
  Pro: High quality lens, optimized for short focus distances,
       flat field, many of them also work for infinity w/o
       changing a thing.  Easy to use: set the magnification and
       reach focus; no need for fumbling with tubes, bellows or
       front-lens converters.
  Con: AF focussing in macro usually isn't --- focus by changing
       the distance.  You get less light in macro settings (the
       nominal, 'printed' aperture is corrected downwards due
       to the short distance.

  Be aware that the working distance (front of lens to object)
  is much more important than the closest focussing distance
  (which is from the film/sensor plane) since the length of
  the lens is _very_ important.  Also check if the lens extends
  during focussing.

Be aware that you'll either want flash or a stable and flexible
tripod: you need tiny apertures to get a millimeter or so of
field of depth at 1:1, and thus need long exposure times w/o flash.

You can supplement most of these methods by adding an
extender/converter, but be aware that the image quality will
degrade (degrade further, actually, in all cases but the true
macro lens).

-Wolfgang

 
[0] Canon's 70-200mm Ls are excellent lenses and can rival quite
   a few fixed focal length ('prime') lenses in image quality,
   especially at the long end (but not weight and price, and not
   necessarily in open apperture, either --- think 85mm f/1.8
   and f/1.2).  Other zooms are more compromises.  
   You get what you pay for, or less, never more.
 
[1] the area of sharpness for a normal lens is a sphere, which does
  not matter at infinity, since then the part of the then
  infinitely large sphere is flat for all purposes.
  However, at close distances the sphere is small against
  the area that is beimg used ...

Sorry mistyped, it is the Sigma 70-300 f/4-f.5.6
in fact it is this one right here
<http://www.bhphotovideo.com/bnh/controller/home?
O=8429&A=details&Q=&sku=391074&is=REG&addedTroughType=categoryNavigation>

Scott

You must have the old version. Most of them have a defect causing
unsharpness when used vertically. Canon fixed mine, and that also
eliminated zoom creep.

KS