G'day
Spied a largish bearded dragon (spiky lizard about 55cm long) in the back
yard this morning. Came in to get a camera, musing over which lens to use.
Thought about a 180 with 25mm ext tube to give good working distance, -
these fellas can be timid and are prone to scramble off up the nearest gum
tree 1 second before the shutter is pressed. Finally decided on the 135
macro + telescopic tube, good compromise between reasonable working
distance & ability to get really close for a head & shoulders portrait if
he stayed still long enough. Turned out to be the right choice.
The episode started me thinking about macros & working distance & 200mm
macros made by certain competitors. I then remembered that John Shaw in
one of his books stated that a with macro lens, using a TC between the
extension tubes & the camera multiplies the magnification ratio, whereas
used normally between the lens & the camera, a TC multiplies the focal
length. Because the 135 macro behaves much like a normal lens when mounted
on the telescopic tube, (in that it focuses to infinity as well as to 1/2
life size), I figured that maybe adding a 1.4x TC between the telescopic
tube & the camera ought to multiply both the focal length & the
magnification ratio. ie provide a 200mm lens that focuses from infinity to
less than 1/2 life size, with heaps of working distance close up.
I tried it and compared it to a 200/5. Focused at infinity, it certainly
seems to be around 200mm. At full extension, it will focus to a minimum
field size of 58mm x 38mm (approx). Without the 1.4x TC, minimum field
size is approx 80mm x 53mm (not quite 1/2 life size), with a working
distance of 405mm from the lens front. At the same magnification (field
size 80mm x 53mm) , the working distance with the 1.4x TC combo is 532mm.
The gain in working distance is 127mm, which could be useful in some
situations. I'll give it a try to see how the image quality holds up. In
theory it should be OK as both the 135 macro & 1.4x TC are good performers.
Has anyone else tried this combo? If so, any opinion regarding image
quality?
Cheers
Ross Waite.
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|