magnification conversion: tubes etc

[Jonathan]

Ok I am pretty sure that for magnification you take the length of the extension tube over the length of the lens. This however is for full frame. Anyone know how to add in the crop factor of say 1.3? This is all to calculate say 1:1 or 2:1 or 3:1 magnification tables if I am unclear(i ramble)/. Would say 0.7 be 1:1 on a 1.3 crop

[sikoragirl]

hmmm...I am curious how crop factor affects magnification...I've seen this to use- it does it all for you:
http://www.eosdoc.com/manuals?q=jlcalc
There are assumptions involved in any of these calculations, so if you want really accurate answers you gotta make measurements with your own equipment like for macro work. I don't think that crop factor affects magnification, but it does affect the field of view...like the size of the subject at the focus plane?..not sure though =-)

[Rudi]

Sounds almost right to me, Jonathan, but then I'm too lazy to think about it! :D You always get "closer" with a crop sensor, and they label crop sensors according to their "magnification" compared to full frame (1.3x, 1.6x, etc.), so it sounds almost right to me... 0.7x magnification on full frame would be around 0.91x on a 1.3x crop sensor (0.7*1.3=0.91). :) And sikoragirl is right, it's not real magnification, just a crop - just as it's not real reach with telephoto lenses on a crop sensor body, it's a crop. For your purposes, though (macro shooting), the result is the same (slightly more DOF, but you want that for macro shooting anyway...).

[Jonathan]

Sounds almost right to me, Jonathan, but then I'm too lazy to think about it! :D You always get "closer" with a crop sensor, and they label crop sensors according to their "magnification" compared to full frame (1.3x, 1.6x, etc.), so it sounds almost right to me... 0.7x magnification on full frame would be around 0.91x on a 1.3x crop sensor (0.7*1.3=0.91). :) And sikoragirl is right, it's not real magnification, just a crop - just as it's not real reach with telephoto lenses on a crop sensor body, it's a crop. For your purposes, though (macro shooting), the result is the same (slightly more DOF, but you want that for macro shooting anyway...).

makes sense to me.
Even with a bellows system giving at maximum length 130mm it wont bring a 1:2 to 2:1 magnification
now 63mm in extension tubes would give me 1:1 but why not start with a macro lens yielding 1:1....sigh