Daily Life

Still at Herman’s!

This was taken with a 40 year old Olympus Zuiko 50mm Macro lens from days long gone by.  It is completely manual on my Canon, and I did not record the f-stop.  It was mostly wide open, so it was probably about f3.5.

(0.7s f/0.0 ISO100 50mm Canon 7D)

The same flower with 50mm of extension tube between the lens and the camera body.  The lens by itself on the Olympus OM 35mm film bodies was capable of 1:1 magnification; that is, whatever you took a closeup photo of, the image on the film was exactly the same size as that object.  With extension tubes of the same length as your lens’ focal length, you could do this with any lens; i.e.: a 75mm lens with 75mm of extension tube gives a 1:1 image.  So 50mm on a 1:1 macro should yield a 2:1, or twice life-size image!

(I needed to be just a little nearer the flower for the 1:1 effect without the extension tubes, but it is close!)

(1.5s f/0.0 ISO100 50mm -1/2 stop 7D)

Pretty neat.  But Wait!  I have lots of old Olympus stuff; lets see what 100mm of extension tubes will do!

(0.3s f/0.0 ISO160 50mm -1/2 stop 7D)

3:1!

Well…nothing works out that easy, unfortunately.  The Canon 7D body I use is a “crop sensor” which means the digital sensor is actually smaller than a 35mm film frame, which is the standard everything is judged on.  It has a 1.6 crop factor.  This means if you use a 50mm lens you need to multiply the 50mm by 1.6 to see what your effective focal length is.  50mm = 80mm.  So you need 80mm of extension tube to create a 1:1 image on a standard lens.  Because this is a 1:1 macro lens already, my slightly over 100mm of extension tubes makes this between 2:1 and 3:1, and I am not going to worry about just what it actually works out to; this is a photo of a really small part of a small flower!

~Curtis in /\/\onTana! {!-{>