View Full Version : Technical info required.

David Morison
16th April 2011, 07:21 PM
For an uninitiated person such as I, could somebody explain what makes a macro lens macro? I realise the configuration is designed to give minimum distortion at close focussing distances but is the magnification simply a factor of focal length and closest focussing distance and what is the formula for this?

I am asking this because there doesn't seem to be a direct correlation between magnification and the above two factors:

ED 35mm - cfd 14.5cm 1:1
ED 50mm - cfd 24.5cm 1:2
Sigma 150mm - cfd 38mm 1:1
Leica 14-150mm @150mm cfd 50cm 1:3.6

Please help me understand what's going on here.



16th April 2011, 07:33 PM
In the good ol days :rolleyes:

A Macro Lens was able to produce an image the same size as the subject on the film (1:1)

Over the years the term "macro" has become linked more to close focus, for the marketing of cheap lenses.

Not sure that there is a formula for all this but as long as you can get a 1cm long subject to cover 1cm of the sensor/film then thats "Proppa" Macro :cool: