An Introduction to Focus Stacking
Macro photography is a great field to have fun and experiment with. It allows you to slow down the capture process and fine tune your settings to realise your creative vision. One aspect of macro photography you may wish you had more control over is depth of field. When we think of depth of field it's usually associated with a portrait where we might want a very narrow focus to separate our subject, or in the case of a landscape it could be everything in focus. Despite the tiny size of the subject, macro photography can often result in extremely shallow depth of field which may look creative but doesn't reveal all the intricate details throughout the image as below.
Stopping the aperture way down on a macro lens isn't always a solution to this problem. Most lenses will show their peak sharpness at around f/8, using a smaller aperture will increase your depth of field but may also begin to soften your image due to an effect called diffraction. In a basic sense, diffraction is the scattering of light as it is forced to pass through a small opening. This light now reaches your camera sensor in not quite the right spot and as a result the image looks slightly out of focus. Selecting an aperture of f/32 for example may get your entire macro subject "in focus" but will almost certainly lack the biting sharpness desired.
So what if there was a way to combine the sharpest aperture of our macro lens and achieve a depth of focus throughout the image? Thankfully there is, it's called Focus Stacking and it's easier than you might think. To get started with focus stacking you'll need a couple of things:
- Your camera, macro lens, a suitably small and stationary subject
- A sturdy tripod and cable release trigger is very helpful
- Fixed position lighting: can be either natural or artificial
- Manual focus and manual exposure settings (or your images won't match!)
- Software for stacking such as Photoshop/Photoshop Elements or Helicon Focus
The setup is just like any other macro photo but instead of taking just one image we'll be taking several and shifting our focus point between each image. How many photos you require to complete the stack will depend on the size of the subject and a bit of trial and error. Aim for around 8-12 images to begin with. If your camera has a "Live View" function and/or Depth of Field preview this will greatly help you visualise how the plane of focus moves through your image. Below is a series of images I took at f/8 in preparation for stacking.
Open your stack in Photoshop making each image its own layer. If you imported your images into Lightroom first you can select the set there, right click and choose "Edit In -> Open as layers in Photoshop". With your images neatly arranged as layers, select all the layers and choose "Edit -> Auto-Align Layers". We're aligning the layers because most lenses actually change their view slightly when shifting focus, this is called Focus Breathing. In regular photography it's barely noticeable and has no impact on a single image, however a macro stack with multiple images of varying focus can show a lot of breathing. After the alignment is completed you can crop away the outer edges.
We're almost done! Select "Edit -> Auto-Blend Layers" and check the seamless blend box. It may take up to a few minutes for Photoshop to process the stack but when it's done you should have an image with focus throughout. Merge the layers together to preserve the blend and finally save your file.
Final image of the fork using the focus stacking technique
Final image of the flower using the focus stacking technique
Picture of a leaf using the focus stacking technique
This blog has been prepared by Ryan from our Brisbane store. Ryan is a wealth of technical and practical photographic knowledge. He is always willing to share his know how at a level everyone will understand. The next time you are in our Brisbane store say hi.
February is Macro Month at Digital Camera Warehouse. If you want more information regarding macro photography techniques and you live near one of our stores, we are running a number of macro photography photo walks at some locations. We will also have a macro photography setup in each store so that you can get hands on and learn more about the gear you might require. Finally make sure to check out some of the macro shots taken by some of our staff on Instagram during the month of February.