My take on focus stacking
One of the reasons that I like macro photography is its ability to reveal detail that is not normally seen with the naked eye. Generally speaking, the more depth of field, the more subject detail will be revealed. Although differential focus can be used to accentuate features such as the eyes of insects, I usually like to have as much as possible of the insect sharp. To this end, I often attempt to get the body of an insect parallel to the camera sensor. Until image stacking was available, I had to balance the extra depth of field of a small aperture with the loss of detail due to diffraction. As I moved beyond 1:1 magnification into extreme macro, the need for increased depth of field became even greater.
To get greater magnification than is given by a standard macro lens, I attached a reversed Nikon enlarging lens to extension bellows. For even more magnification, I used 4x and 10x microscope lenses on the bellows. When taking a set of images for stacking, either the lens can be focused at increasing distances or the camera and lens can be moved forward toward the subject. My first shots used the cross slide of a small lathe to change the camera and lens to subject distance. I started with the camera focused on the nearest point of the subject, took a shot, moved the cross slide forward with the micrometer handle and took another shot. I repeated this process until I reached the far point of the subject.
As I found taking a couple of hundred shots by the above manual method rather tedious, I bought a Stackshot Rail Package to automate the process. With this equipment, I only have to set the step size and near and far focus points before the Stackshot takes the set of images for me. Initially, I used my extreme macro set up in the horizontal position but then built a vertical stand to enable specimens on microscope slides to be photographed.
My next equipment purchase was a microscope to which I added a stepper motor to drive the fine focusing control. The microscope gives more lighting control, easier filtration and more control of subject position than my extreme macro set up. I drive the stepper with the Stackshot control unit. As the length of the tube which connects the camera to the lens is fixed, so is the magnification of each microscope lens. To effectively increase the field of view when a subject is too large for a particular lens, I take side-by-side stacks of shots in panoramic fashion. The resulting stacked images are stitched together using Photoshop. As may be imagined, this process takes a while but results in very large, detailed images.
Stepper motor fitted to microscope
Multiple stacked images to enlarge field of view
When focus stacking with a normal macro lens ‘in the field’, I have used a Helicon FB tube to automatically advance the focusing. Now that I have a Canon EOS R5, I use the built-in feature to take stacks of images. I have occasionally taken focus stacks of flowers with just a macro lens by simply moving the focus forward manually.
When processing stacks, I use Capture One to edit and export the RAW images as 16 bit TIFFs. I then use Zerene Stacker to combine the images into one sharp-all-over image. Finally, I use Photoshop to do any editing such as combining panoramic images and cleaning up.
Whereas with single shot photography a sufficiently high shutter speed will prevent image degradation due to subject/camera movement, with stacked images there is the extra danger of movement from one image to another causing problems. Zerene Stacker may be able to cope with some movement of the whole subject between frames but individual leg or wing movement may not be easy to deal with when retouching the image in this program. I have found the movement between frames of overlapping dragonfly wings to be particularly troublesome. In my experience, windy days are best avoided when taking image stacks outdoors.
Although, because it is easier, I have written this post as if I have worked alone, my wife has done more extreme macro than I have and has been more successful with her microscope images. She is also better than I am at processing stacked images.
I have included a few stacked image examples below and more can be seen in my recent posts.
Nikon enlarging lens on bellows
Nikon enlarging lens on bellows
Nikon enlarging lens on bellows
4x microscope lens on bellows
4x microscope lens on bellows
4x microscope lens on bellows
10x microscope lens on bellows
Microscope polarizing filters Vitamin C
Microscope 4x lens polarizing and wave plate filters
Microscope 4x lens polarizing and wave plate filters
Microscope 4x lens polarizing and wave plate filters
Microscope 4x lens polarizing and wave plate filters
Stacking with Helicon FB Tube
Canon EOS R5 built-in stacking
