Some macro lenses seem to offer various levels of zoom - should I be looking at a prize macro, or is a zoom macro acceptable? (is my terminology correct?)
Can a macro lens be used as a portrait lens? I'm not sure if that's the correct question to ask... I suppose I'm trying to ask what it is that makes a macro lens a macro lens - is it purely the closest distance at which the lens can focus? So many numbers and letters to understand!
Think of macro as a lens ability to reproduce a subject life-size on the image sensor--that is, the size of an object is exactly how much space it will take up on the physical area of the sensor surface. Life-size would be 1:1, half life-size would be 1:2, quarter life-size would be 1:4, etc... and remember that these measures are in area, not linear distance.
True 1:1 macro lenses are usually prime lenses with a single focal length, though many of them appear to "zoom" in actual use, while they are merely focusing. If you had two identical cameras and a 1:1 macro lens, you could take a picture of the image sensor of the other camera and focus so closely that the other sensor would fill up the image frame. Some prime macro lenses will have less magnification, as little as 1:2, and some will have more, up to 5:1 (5x) or more.
When a zoom lens offers "macro" ability, what the manufacturer means is that they have designed the lens to be able to focus on objects fairly
closely, closely enough to be competitive against competitors zooms, but they might only offer a magnification ratio of around 1:4. This maximum magnification ratio might only be available at one focal length in the zoom range. Starting out, this might be all you need, but don't expect to fill the frame with a lady bug using a zoom lens.