ApertureAperture is how much you open the hole in your lens, it shows as f/"value" in your camera. The wider it open the smaller the value, and vice versa. Aperture is used to control the amount of light that will enter to the camera. But beside that, aperture can also control the DOF area. The wider aperture (smaller f/value), more shallow DOF you will get. And the smaller aperture (bigger f/value), the deeper DOF area you will get.
|F/16, shallow DOF|
|F/22, deeper DOF|
Magnification in Macro Photography is a must. A macro picture should have at least 1:1 magnification ratio. It means, the length of the object taken on sensor has the same length with the real object. For example, if you take a coin with 10mm in diameter, then the coin's picture on sensor also has 10mm in diameter. That's what you call 1:1 magnification ratio.
Magnification depends on the distance between object and sensor. When you get closer to the object, then more magnified the sensor will take the object. Magnification and DOF has negative relationship. When you get the high magnification, then the result is you get shallow DOF, and vice versa. When you get less magnification, you will get deeper DOF.
|Distance between object and lens is about 15cm. Picture was taken using macro lens Nikkor 85mm Micro|
|Distance between object and lens is about 5cm. Picture was taken using macro lens added by close up filter +10|
How to Control DOFAfter you know what are the factors that influence DOF, then you can control how deep DOF you want to get. In Macro photography, detail, focus and sharp picture is essential. Then, controlling DOF is an important thing you should do while taking Macro picture.
Since magnification is essential in Macro Photography, then the one you can control is Aperture. I usually use F/8 or smaller (bigger F/value), depends on the angle of the object. When you take the angle from the side of the object, then F/8 until F/10 is enough. But when you take the angle from the front or from the face of the object, F/13 or smaller is used.
What if the picture I get become under exposure? You can use built-in flash or external flash. By using flash, you can control DOF easily by changing the value of aperture, and you still can use fast speed on your shutter.
One more thing while using flash, don't forget to use flash diffuser to prevent harsh lighting over your object. Harsh lighting will reduce detail and sharpness of the object