Magnification calculation help

[anandonaqui]

I was messing around yesterday with my lenses and got the following result:

That's part of the E in CENT on the back of a penny

I used my 70-300mm sigma, which is a "macro" lens (not really, it goes to 1:2) at 300mm on a 66mm extension. I know I could calculate the magnification myself with that info, but I also had a 50mm reversed in front of the 70-300.

For the record, that setup is a huge pain to shoot with. Thanks for you help!

 

[iamsneaky13]

300mm/50mm is 6:1, regardless of the focussing distance( mag). i do not know how much the extension tube adds, but it could be very little.
I have not tested this setup with extension tubes, but putting them in between the 50 and the 300 should increase it more than between the 300 and the camera.