Tuesday, January 8, 2013

Focus Stacking in Macro Photography

This technique is primarily used in macro photography. Depth of Field (DOF) is limited by default in macro photography because you have to get very close to the subject. Typically you will want to use a small aperture (F11 to F/16 is recommended) with either a slow shutter speed (around 1/250), bright lighting, and/or a high ISO.

The slower the shutter speed the more likely you will capture motion which will reduce sharpness. A high ISO will introduce noise into the picture as well. Whether you are using an actual macro lens, a telephoto lens with macro capabilities, or a close-up filter and the minimum focus range available on it will also make a difference on your DOF. In other words, all kinds of things can reduce the DOF and/or sharpness in macro photography.

To get a completely sharp close-up picture of a small object you can use the technique called Focus Stacking. In focus stacking you need to obtain multiple images of the same subject at different focus points of the subject. The subject needs to be still while you are taking the pictures or the images will not align properly in post processing. Therefore, you will want to control wind around the subject. It also means, unfortunately, dead insects. I have heard that if you catch a live bug and put it in the freezer for a little while they will stay still long enough to take some photos without killing them. I personally, do not want to test this.

The first part of this process is to get the necessary images.
  • Set your camera to full manual mode (flash, shutter and aperture) to manual.
  • If your camera has live preview enable this feature and zoom in on the display so you can see clearly where the focus point is for each particular shot.
  • Use a steady tripod.
  • Use a cable release or remote control to minimize camera shake when you press the shutter button.
  • If you camera has the ability to lock the camera mirror, use this feature as well, if possible (i.e. you have the patience to set it up). This article has a very good explanation and examples of how camera shake can be introduced when the mirror flips up while the image is captured. http://www.cameratechnica.com/2011/04/26/dslr-mirror-lock-up-worth-the-effort-or-not/
  • Set your lens to manual focusing so you can slowly move the image’s point of focus for each capture.
  • For this technique try to create soft, even lighting around your subject. See this article on how to create a cheap macro photo studio: http://strobist.blogspot.com/2006/07/how-to-diy-10-macro-photo-studio.html.
  • Take as many photos as you can, 30+ is not unheard of, starting at one end and ending at the other end. The number of pictures you need to take will depend on the DOF you have available with your particular settings and the size of the object. Obviously, an image of a bee at very close range will require more photos than a flower at a longer distance. The closer you get to the subject the shorter the DOF will be.
  • Try to leave sufficient room all around the image for cropping later on in the editing process.
In addition to these manual techniques there is software available that allows you to remote control your camera from a computer using a USB cable. Typically, these kinds of software will allow you to display live images on the PC screen, auto focus and manually control focus from the PC, see large high quality previews of shots immediately after shooting it.

 There are many more out there. I just found these on a quick Google search. I have not used any of them so I cannot comment on how good or bad they might be. Always check out reviews of any software you plan to install on your computer and use with your camera.

To actually stack the images you took you can use focus stacking specialized software. Some of them are listed below. You can do this manually in any image editing program that supports layers and masks. As you can image the manual method is more labor intensive and time consuming.

These are some examples of stacking software that does this automatically:
You can see some examples of focus stacked photos on these sites:

 Flickr Slideshow of user submitted examples:

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