How to calculate macro magnification? Some photographers add on close-up filters , extension tube or teleconverter to maximize the macro magnification and wonder what magnification ratio they are shooting at. It is very simple, you only need a ruler.
Magnification = sensor width / # of mm captured
= 22.2/22
= 1X (approx)
Magnification = sensor width / # of mm captured
= 22.2/11
= 2X (approx)
Magnification = sensor width / # of mm captured
= 22.2/7
= 3X (approx)
Add the native 1X from the macro lens and you get 1.68X. However, the actual measurement tells us you can get up to 2:1 magnification. It is even more surprising to hear that you can get up to 2:1 too on the 150mm.
Life Size (1:1)
It's all depend on your camera's sensor size, please refer to your camera specification to check the sensor size, or you can check your specification on www.dpreview.com .
For example, an APS-C DSLR, Canon EOS 60D's sensor size is 22.3mm x 14.9mm (from dpreview). A 22.3mm long subject fully fills up the width of the 22.3mm sensor, then it's life size magnification (1:1).
By looking at the ruler above, you see approximately 22mm there, therefore it's 1:1 (life size).
Magnification = sensor width / # of mm captured
= 22.2/22
= 1X (approx)
Magnification = sensor width / # of mm captured
= 22.2/11
= 2X (approx)
Magnification = sensor width / # of mm captured
= 22.2/7
= 3X (approx)
(Taken from http://orionmystery.blospot.com)
Illustration above shows you the different magnifications when you shoot a real life subject at different magnification and also with a FF (Full Frame) camera. Let us assume the soldier fly image was shot with a 60D (crop sensor) at 1:1. The yellow, red and blue frames are what they would look at at 2X, 3X (crop sensor) and 1X (FF) respectively.
Based on the input from a few forum members, you can get up to 2:1 by adding a full set of 68mm of Kenko Extension Tubes to a 90mm, 100mm, and 150mm macro lens.
Theoretically, the calculation goes like this:
Magnification gained = # of mm of tubes used / focal length
so if you used all 68mm of tubes on say a 100mm, you should gain an additional 68/100 = 0.68X
Okay, I know you magnification junkies out there won't be happy with 2:1, you want more. You can still add a 1.4X Teleconverter to your setup and get up to about 2.5X. Actual macro magnification may vary so again, go shoot a ruler. So the best way to calculate/measure macro magnification is to shoot a ruler.
