Focus Stacking How To:

The Overview. There are several different ways to create a stack of photos. You can move the camera, the subject, or change the distance between the lens and the camera. Typically the camera's position is adjusted in relation to the subject of interest by using a macro-rail. It allows finely controlled movement of the camera to change the distance between the camera and the subject. This movement slides the in-focus part of the image through the subject. There are more educational links about focus stacking at the bottom of the page. If you've done this before you know it can be a slow and tedious task. Take picture, move rail slightly, take picture (ugh! Did I just bump the camera?), move the rail a little more, and then as if fate knew you hauled out ten pounds of camera gear, the insect you were photographing flies away. So what does Cognisys have to offer the world of focus stacking? StackShot. StackShot automates the movement of the rail and the triggering of the camera's shutter. This precision controlled rail will take as many pictures you want at whatever step size you'd like (down to 0.01mm). So how does it work? Let's first start off with the connections involved.

The Equipment. There are plenty of options in the photographic world for taking macro photographs, macro lenses, microscope objectives, bellows, inverted lenses, extension tubes, etc. Use whatever lens and camera setup you are comfortable with. The first thing that would be useful is determining the depth-of-field (DOF) of your lens and aperture setting. Consult your lens manual and see if they specify the DOF for a given aperture. In this example with the Canon MP-E 65mm, at 5x magnification and f/8, the DOF is 0.249mm. If your lens does not have a chart or graph indicating the DOF at a given aperture , an excellent resource for determining it is here .

The Process. The first step in the stacking process is to adjust you camera and flash settings to get proper exposure. The one difference for focus stacking is that you will want to use full manual mode for both the flash, shutter and aperture. The auto exposure modes tend to meter the scene a bit inconsistently causing a significant variation in brightness of the photographs over the range of images in the stack.

In this example we're going to use the "Auto-Distance" mode in StackShot. Since the DOF is 0.249mm, the "Distance per Step" variable in the controller is adjusted to 0.150 mm. It is desirable to have some overlap of in focus depth between photographs. Using the FWD and BACK buttons the position of the camera is adjusted to the initial starting point for the first picture in the stack. StackShot will travel in both directions so it can stack from the foreground to the background or visa versa. Pressing the Up/Down button sets the starting point for the stack. Then the position of the camera is adjusted to the final position of the stack. One more button press initiates the capturing process and the camera is moved by the distance entered (0.150 mm) with a picture taken at each step. After the rail takes a step there may be some unintended motion in the camera due to the setup. A configurable "settle" time may be adjusted to meet the specific needs of the shooting environment. What about exposure bracketing? StackShot can be configured to generate multiple shutter pulses (exposures) per step. This feature may also be useful for cameras that require a preliminary shutter press to activate mirror lock-up. A configurable delay between pulses allows additional fine-tuning. At the end of the process StackShot defaults to returning to the starting position. This lets you experiment with different camera and/or flash settings for subsequent runs. You might want to shoot a place holder shot of your hand between runs to act as a book-mark.

The stack of images is collected. Now what?

Software. Now it is time to use the software of your choice to combine the images. There are several possibilities including Helicon Focus, Zerene Stacker, PhotoShop, or Combine ZM. Both Helicon Soft and Zerene Stacker offer 30-day evaluation versions, they can be downloaded here:

Other Resources.Here are a few web sites that go into more detail about the Focus Stacking process:
Focus Stacking Articles - Laurie Knight does an excellent job explaining the in's and out's of focus stacking including tips and tricks as well as common problems.
Photomacrography Forum - Great forum for anything related to macro photography
Focus Stacking Video - You-tube video by ePhotoZine.tv

The Results.

This is a picture of a Maple Stamen. The picture was taken with StackShot and a 4X microscope objective. It contains 26 frames separated by 50um. Click on the image to see a movie made up of the individual frames. The movie shows the very shallow depth of field in the individual frames. Thanks again to Linden for the use of his pictures.

 

This picture of the Cithaerias Aurorina butterfly wing was taken with a 10X microscope objective. The image is the compilation of 39 individual pictures collected with the help of StackShot and then merged together. Each image was taken at a step size of 0.01mm.

 

The moth above was taken using a 100mm f/2.8 Canon Macro Lens and StackShot. This moth was hanging on our glass sliding door. The smaller pictures below are the first and last images from the stack. This gives you an idea of the depth of field you would be restricted to without focus stacking.