Image stacking - for increased depth of field

A microscope is not only useful when investigating microscopic specimens. To see the fine details of insects and other larger specimens, a microscope is also extremely handy. However, the depth of field (DOF) is very shallow and only a small portion of the specimen can be in focus at each time. This is not due to bad objectives or microscope, but due to the high magnification. But this problem can easily be overcome by the use of an image processing method called focus stacking.

Illustration of the shallow depth of field.
The focus plane is at the top of the right eye and mouth

Focus stacking is a technique that uses software like ‘Helicon focus’ and ‘Photoshop’ to blend different images of the same object together to get the entire specimen in focus in a single image. This is done by taking an image of each focus plane as you change the focus all the way from the top of the specimen to the bottom. These images are then loaded into the software, which then masks out all the blurry parts and combines all the shap parts, leaving a single sharp image.

The stacking of this hoverfly lets us see all the individual hexagonal ommatidium of the eyes in focus at once. These structures make up the insect's compound eyes and contain the photoreceptors cells enabling the fly to see. All the ripples of the labellum (mouth part) are also clearly visible. These ripple aid in the transportation of fluids into the mouth which functions as a straw. All the individual fine hairs and sensory antennae are also all sharp at once. Without focus stacking, most of these would just be one big blur.