What is Macro Photography?
First, an explanatory note for all those with a modicum of photo history and tech basics: the term macro used to refer to the capture of an insect or whatever, that resulted in an image on the 35mm film frame (24x36mm) that ranged from 1:10 to 1:1 the size of the original subject. For its part, the term micro referred to a film image that was larger than 1:1 life size; micro photography could easily give you a 35mm film image of an ant that was itself larger than the original ant.
A CCD or CMOS sensor can be as tiny as 3x4mm, so any definition term that applied in the film days is now obsolete. But the rules that apply in accomplishing successful and satisfying macro photography still stand.
Normal photography works in using a camera to record a sharp image by adjusting the lens-to-sensor distance to attain precise focus: for distant subjects at infinity, like landscapes, the lens is positioned at a minimum lens-to-sensor distance; to capture sharp images of closer subjects, like people, the lens-to-sensor is increased.
In macro photography, a sharp image of a tiny object requires the lens to be positioned much closer still, with the lens moved even further out than for normal photography.
As far as my investigations go, just about all compact digicams and most dSLRs have a selectable macro mode. In some cameras you can select macro mode via an external control, while in others you must access the viewfinder menu.
Think about it: no extra lenses, no macro tubes or bellows, no special lenses. What a wonderful world in which to shoot macro!
Tips for Macro Photography Beginners
Being curious about how digital cameras can capture macro so easily I investigated the subject. Here are my findings, gained by chatting to the tech expert at a major camera company.
Engage macro mode on a digicam and the system adjusts the lens elements to re-arrange them into an array that best suits close focusing. Quite a feat, as even simple camera lenses have a surprising number of lens elements to juggle.
Unfortunately, by engaging macro mode with the vast majority of cameras you lose control of both the lens aperture (f-stop) and shutter speed.
Why is this so important?
The best macro photography — regardless of camera — requires that you use the smallest lens aperture to gain optimum image sharpness and depth of field. Using a small lens aperture means you need more light, so you need to extend the exposure time to make a correctly exposed photograph.
So you can’t reduce the lens aperture to a smaller, more favourable setting; nor can you slow the shutter speed to permit the use of a smaller lens aperture.
For the keen macro makers I’ve discovered a few digicams that do allow the use of macro mode and lens and shutter speed adjustment (see Chosen Few).
With DSLR cameras the macro operation is somewhat different. Select macro and you activate a different chain of events: with any lens fixed to the camera, engaging macro mode on the camera commands the lens aperture to close to its minimum, so extending the depth of field and allowing you to move closer to the subject.
Shooting macro with a compact digicam is easy but you have to forgo a fair bit of control and you need to understand that the demands of an amateur as far as resolution and colour quality are less stringent than the pros.
The pro approach would be to use a purpose-built macro lens on a DSLR. Dedicated macro lenses are not cheap but they are optimised to operate at closer than normal distances. With macro lenses you are unlikely to experience problems such as colour fringing and optical distortion; many macro lenses also compensate for the additional exposure necessary when racking out the lens to distances very different to those used in normal photography.