What Makes a lens "Macro"

[jamesev]

Reading reviews on the Sigma 70-300 suggests it has a special fuinction as a Macro lens

However the Nikon 70-300 isn't classed as Macro

So what makes a lens a "Macro" photography lens?

[inkista]

In the case of the Sigma, ignoring what most people mean by "Macro."

The Sigma and Nikon 70-300s pretty much have the same macro capability. Neither one is particularly good at close focus. The Sigma only offers 1:3 magnification, while a "true" Macro lens generally offers 1:1 magnification (i.e., the image on the sensor is the same size as the object in real life).

A true macro lens will be a prime. It will typically have a very small minimum focus distance, floating element design, and offer 1:1 magnification or better.

Get the 70-300 because you want a telephoto zoom, not because you need it to be a closeup lens.

[jamesev]

Originally Posted by inkista

In the case of the Sigma, ignoring what most people mean by "Macro."

The Sigma and Nikon 70-300s pretty much have the same macro capability. Neither one is particularly good at close focus. The Sigma only offers 1:3 magnification, while a "true" Macro lens generally offers 1:1 magnification (i.e., the image on the sensor is the same size as the object in real life).

A true macro lens will be a prime. It will typically have a very small minimum focus distance, floating element design, and offer 1:1 magnification or better.

Get the 70-300 because you want a telephoto zoom, not because you need it to be a closeup lens.

So what are the benefits of each type of Macro lens
say 50mm vs 105mm

[RichardTaylor]

The longer macro lenses give you more working distance to the subject which can be a real help with "skittish/dangerous" subjects and a lot easier in lighting the subject.
Downsides are physically larger.
Another difference, not necessarily an advantage, is a perspective change.

[rzhong]

A macro lense generally allows you to focus closer to the subject your trying to shoot.

Example:
Canon 100mm f/2 non macro: closest focusing distance is .9m/3ft
Canon 100mm f/2.8 macro: closest focusing distance is .31m/1ft

Be sure to check the focusing distance when selecting a lense and if that works for what you plan on doing.

Also, if you get into portrait photography, the longer the focal length, the further back you can stand from your subject.