Focusing for Up-Close Work
When working up close, autofocus can cause some problems. The range of focus that gives sharpness is very narrow up close, so you have to be sure where your camera is focusing. There are so many things close together when shooting close-ups that the camera may have trouble deciding where to focus, and often it will focus on the wrong thing.
Your focus point is really critical up close, as seen in Figures 9 and 10. Missing it can make the difference between what a viewer thinks is a sharp picture, and a photo that is not sharp (even though something else in the photo might be sharp). For example, if you photograph a grasshopper, that grasshopper's eyes need to be in focus, or the viewer will think the image is out of focus.
Figure 9 Honey bee, zoom and achromatic close-up lens.
Figure 10 Flower fly, zoom and achromatic close-up lens.
Manual focus is sometimes easier to use up close than autofocus, because the manual focus doesn't change except when you want it to change. You can lock it in on exactly what you want to be in focus. But that doesn't mean you can't use autofocus for this purpose. You just have to be aware of what your autofocus is doing. It often helps to limit the focus with a focus lock button (some cameras have these on the back of the camera) or by pressing the shutter halfway. You can move the camera around to force it to focus where you want, lock the focus, then reframe for your shot's composition.
A trick that can help with sharper focus is to do your rough focus manually or by locking focus, and then move your camera and lens gently toward and away from your subject until the important part of it is sharp.