Focus stacking is a digital image processing technique which combines multiple images taken at different focus distances to give a resulting image with a greater depth of field than any of the individual images. Focus stacking can be used where individual images have a very shallow depth of field such as close-up and macro photography. Focus stacking can also be useful in landscape photography where the focus ranges from near to far is too great for a single image. Shooting a series of images with varying focusing distances can be a solution. This image sequence can be combined in post processing software to create an infinite depth of field.
Each image has its own tiny depth of field, but not enough to cover the entire object. These individual slices of sharpness are of course influenced by the aperture. Stopping down more or less will give a greater or lesser depth of field in those slices.
This will determine how many stack shots you would need. If you stop down to f22 or less, you would need fewer stack shots to cover the range. Once you get down to Micro photography using microscope lenses to photograph the eyes of the bee, it is possible that you would need 100 stack shots or more to cover the depth of field required.
When is this technique useful? Basically, anytime when there is a situation where the desired depth of field cannot be achieved with one image, not even stopped down to the smallest aperture. The common cases where you could use this is close-up, macro and microscopic photography.
I use it often doing product shoots such as jewelry and other small items. At first it seems a little bit involved and time consuming and maybe it is. But in many cases, there is simply no other way to cover the desired focus depth.
Setting up for a focus stack shoot
Using a tripod or other firm mounting of the camera is almost a must. You can shoot simple focus stacks of 5 shots or less handheld, but for more intricate and accurate work, a sturdy set-up is the key to success.
After picking lens, background, lighting and composition, set the exposure mode to Aperture Priority or Manual so that aperture remains constant ( this is a must ). If the camera is on tripod, disable lens vibration reduction (VR). Another point to consider during setup is the lighting. I won’t go into specific lighting techniques here, but it is important that the lighting is consistent between stack shots.
Shooting a very simple focus stack
This is the simplest way to create a focus stack. No additional equipment or software is required to create a stack using this method. Set-up your object. In this case, I mounted the Cicada skin on an acupuncture needle which in turn was fixed in a vertical position using Seismic Wax or Blue-tack. Add lighting, background, etc. With the camera on the tripod, take some test shots to determine lighting, exposure and composition.
Then, to create a stack, focus on the Cicada part closest to the camera and take the shot. Focus slightly back from that point and take another shot. Continue doing this until the furthest focus point has been reached. I like using this very easy way because it leaves room for creativity. You can create stacks of parts you want to appear sharp but still have some “softer” areas to create sense of depth etc.
Focus Stacking with the Nikon D850, Nikon Z6 and Nikon Z7
The Nikon D850 was the first camera with built-in ‘Focus Shift’ capability. The Nikon Z6 and Z7 take that feature a bit further, thanks to the new “peaking stack image” function. With this new feature, you will be able to see a monochrome preview of the focus stack you are able to capture, which is really cool, as it removes any guesswork while making stacked images out in the field. Apart from that, all three models have this awesome functionality. Before this, shooting a focus stack would always involve controlling the camera via a laptop and control software.
You will obviously need to use third party software to stack images together, but the automation part within the camera is a pretty big deal for product, macro and landscape photographers.
The entire process is controlled by the camera and getting the camera into stack focus mode is pretty straightforward:
From the Photo Shooting Menu, select Focus Shift Shooting.
Start: Start shooting.
No. of shots: Choose the number of shots (up to 300).
Focus step width: Choose the amount the focus distance changes with each shot.
Interval until next shot: The time between shots, in seconds.
Exposure smoothing: If On is selected, the camera will adjust the exposure for each new shot to match the immediately preceding shot.
Silent photography: Select On to silence the shutter during shooting. It also limits camera shake and reduces power consumption and wear on the shutter.
Starting storage folder: Choose New folder to create a new folder for each new focus shift sequence.
· Work with a full camera battery; capturing 120 or more shots will take a while.
· Turn VR off when the camera is mounted on a tripod.
· Take test shots to check exposure and composition before shooting the entire stack.
· Make sure that there is no movement in either the camera set-up or the subject.
· Delicate flowers and plants can move. It can take 15 minutes to shoot one stack.
· Try focus stacking on insects, butterflies, coins, stones, tree bark, jewellery, seashells, electronics, mechanical things and so on.
· Work clean, dust and fingerprints are problematic when shooting macro or micro.
Harry Janssen is an award-winning photographer in the Auckland region and he is an Adobe Certified Expert in Lightroom and Photoshop. Harry Janssen is a member of the New Zealand Institute of Professional Photography and has won numerous awards for his work, including the distinction Grand Master of Photography at the NZIPP Iris Awards.
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