Focus by eye
At high magnifications there is no margin for mis-focusing, so pinpoint accuracy is required for bitingly sharp macro shots
The effects of focusing, or more importantly, mis-focusing, are far more pronounced when you are shooting subjects in extreme close-up, because depth of field is limited to just a few millimetres. It’s possible to increase the depth of field by shooting at a very small aperture, for example f/16 or f/22, but even then the amount of your subject that will be recorded in sharp focus will be limited to a very narrow band indeed.
Also, using such a small aperture may not always be desirable in macro photography, as this can bring the surroundings more into focus, which may draw viewers’ attention away from the subject. In fact, many of the most successful macro shots are taken at quite a wide aperture, to deliberately restrict the point of focus to a very specific part of the subject in order to give it greater impact.
Irrespective of the aperture you decide is appropriate for your subject, precise focusing is vital. This requires a methodical, disciplined approach with a high level of accuracy in both focusing and camera positioning. To achieve the best results you’ll need to take your time, and to make very fine adjustments, as well as make constant checks to ensure you have got the best possible focus.