Originally posted by Stiv
The lens I have is already 1x magnification:
Sigma-MACRO-70mm-F2.8-EX-DG-AF
So does that mean with the Raynox I could achieve 2x mag? And would it also mean I could get 1x mag from further away? With the 70mm my working distance is pretty short.
I was shooting a jumping spider the other day and whenever I got in real close he wanted to jump on the lens!
When you add a closeup lens of focal length f' to a lens of focal length f, the combination has a magnification of m'=f/f'
If the original lens is extended to a magnification of m" before the closeup lens is added, the total magnification m is:
m=(1+m')(1+m")-1
Your 70mm lens plus the Raynox 150 has a magnification of 70/208=.336, and with the Raynox 250, a magnification of .56. When combined with the initial 1X magnification of your macro lens this yields a total maximum magnification of:
Raynox 150, m= 1.67X working distance 208mm
EDIT the working distance is wrong; see my later post
Raynox 250, m= 2.12X working distance 125mm
EDIT the working distance is wrong; see my later post
Dave
PS "And would it also mean I could get 1x mag from further away?" - yes. With the bare 70mm lens the working distance at 1:1 is about 140mm; with the Raynox 150, at 1:1 the working distance would be 208mm - 50% greater.
EDIT the working distance is wrong; it is actually around 104mm - see my later post