Macro help

Let me again expose my ignorance to this welcoming forum. I've just bought cheaply a Miranda 75-300mm macro zoom. I expected it to allow me to zoom in at a greater magnification on distant objects (birds to be precise) than I can with the kit 50-200 DA zoom. The Miranda doesn't do that - it seems to allow me to take (very good) shots at an almost fixed magnification, around what I would get with the kit zoom at 75, with the ability to focus manually from 4.5 feet to infinity. I'm sure there are good explanations of what I need somewhere out there, and I would be very grateful to be pointed in the right direction.

I think first, you need to understand what is meant by macro photography.

Macro photography requires a lens, or a combination of lens and extension tubes, that is capable of producing images at 1:1 magnification, or greater. That is, if a subject measures 1 centimetre in real life, it's image measures 1 centimetre on the recorded image (sensor or film).

This technique requires a lens capable of focussing from very close distances to infinity and the normal macro subject will be very close, like flowers or small bugs.

Your Miranda lens will make a distant subject, like a bird, appear larger when taken at 300mm than it would when using your kit lens at 200mm. Both will render the subject the same size when using the same focal length on each lens.

Zoom lenses claiming to have a macro capability or not true macro lenses, they just facilitate focussing a little closer than you would normally be able to and rarely give a magnification of better than 1:2, or half life sized.

Just to add to Mannesty's comment, a properly designed macro lens will have a flatter field than your zoom making it suitable for copying purposes, too.

This won't matter so much on everyday subjects. But lenses like your Miranda would be more accurately described as 'close focussing'.

Also, since, on macro subjects, you would normally want to focus manually, an f2.8 or better aperture is very useful. Though you wouldn't generally take your picture at such a wide aperture due to the very small depth of field.

Macro has become a much misused term.

Never hesitate to point out the obvious. I had no idea about the push-pull bit. Many thanks to Karma Mechanic - or as we say in Manx, gura mie mooar ayd!

Some lenses operate completely differently in macro mode. The old Pentax-M 40-80mm for example gains push-pull focusing when you click the zoom ring around to macro, and won't click back to being a conventional zoom unless you pull the focus ring all the way back toward the camera and then turn the zoom ring. I'm not sure if there are any others quite like this!