Back Theoretical Kenko Macro Extension Tube Performance
50mm f/1.4 Lens on Canon 40D, A3 print
Extension Tube Length
(stacked combinations in brackets)
12mm20mm32mm
(20+12)
36mm48mm
(36+12)
56mm
(36+20)
68mm
(36+20+12)
Magnification
(size on sensor)
at ∞0.240.400.640.720.961.121.36
at 45cm0.370.530.770.851.091.251.49
Field Coverage
(width × height, in mm)
at ∞93×6256×3735×2331×2123×1520×1316×11
at 45cm61×4142×2829×1926×1820×1418×1215×10
D.o.F. @ f/1.4
(maximum aperture)
at ∞695μm283μm129μm107μm69μm55μm41μm
at 45cm331μm179μm97μm83μm57μm47μm36μm
D.o.F. @ f/11
(diffraction aperture)
at ∞5.6mm2.3mm1.0mm857μm550μm437μm330μm
at 45cm2.6mm1.4mm779μm668μm458μm374μm291μm
D.o.F. @ f/22
(minimum aperture)
at ∞1.1cm4.5mm2.1mm1.7mm1.1mm873μm659μm
at 45cm5.3mm2.9mm1.6mm1.3mm915μm749μm582μm
Brightness Loss
(in stops)
at ∞0.61.01.41.61.92.22.5
at 45cm0.91.21.61.82.12.32.6