Originally posted by cali92rs Macro Extension Tubes & Close-up Lenses This site has a handy dandy calculator that will give different magnifications using extension tubes and also close up lenses.
something is not right about this calculator.
Using their base numbers
Native Magnification 0.15 X
Lens Focal Length mm 50 mm
Total Extension Tube Amount 25 mm
New Magnification = 0.65X
New Closest Focusing Distance* = 209.4 mm.
If you enter a new extension tube number of 50mm you get,
New Magnification = 1.15X
New Closest Focusing Distance* = 201 mm.
If you enter a new extension tube number of 100mm you get,
New Magnification = 2.15X
New Closest Focusing Distance* = 230.8 mm.
The new close focus distance is getting larger not smaller. Which is backwards.
So I cannot trust this calculator.