There are times where no matter the camera settings and combination of lenses used, some area of an image may not be captured to sharp precision due to a shallow depth of field.
Typically, using a smaller aperture may increase depth of field. However, the further one moves the aperture from the lens’ sweet spot (the aperture at which the lens produces its sharpest image – usually found about two to three stops from wide open), lens diffraction may occur and result in some fuzziness1.
This is where focus stacking proves to be extremely useful.
By combining several images shot at different focus distances so that the entire image or subject is in focus – this technique is especially suitable for macro and landscape shots because it is able to capture greater depth of field than could be captured in a single image.
But when and how should one use it to take their photos to the next level?
Additionally, how can the new Nikon D850’s focus shift function help with focus stacking?
By combining images where the focus point is gradually changed, a photographer can end up with a final composite that has a majority of the required areas in focus – through the blending of the separate exposures later using a third-party software.
This technique is commonly used in:
• Landscape photography when foreground objects are too close to the lens to get both the object and background in focus without using a very small aperture and causing softening due to diffraction.
• Macro photography (jewellery, specimen, food) because the closer one gets to a subject, the shallower the depth of field gets.
While focus stacking is not a new concept in photography, often, photographers must manually adjust the focus and take a series of pictures at different focal distances, such that the entire depth of the subject or scene is covered in the series.
For example, if one was shooting a close-up photo of an insect, there should be one photo taken with the fly’s head in focus, another with its body in focus and finally, one with its wings in focus – before blending these images together.
Nikon D850, AF-S Micro Nikkor 60mm f/2.8G ED - ISO100, f/5.6, 1/100 | © Andrew JK Tan
Nikon D850, AF-S NIKKOR 80-400mm f/4.5-5.6G ED VR - 53 images stacked, step width 5, f/5.6 | © Andrew JK Tan
However, there could be several challenges the photographer faces in this manual process, especially if the subject is not stationary, and if nature is involved.
Ideally, to get all the images in a stacking series should be captured at the exact same conditions and parameters: aperture, ISO, shutter speed and white balance. These can change very quickly in-between the time needed for the photographer to manually adjust the focus, resulting in an unsuccessful shot.
While a third-party software is still required to combine the shots, the D850’s focus shift function feature will automatically take shots at a user-specified interval while shifting the focus distance spontaneously to accurately and sharply capture photos with a range of depth of field that covers the entire image area.
As such, users will not need to worry about manually shifting the focus as the D850 automatically adjusts focus distance at precisely calculated points to cover the entire focus range for each scene.
1. A photographer can pick the number of shots and a step number for how much to move the focus between each shot (with the D850, the focus step width can be selected from 10 levels).
2. Pick the starting focus point (by setting focus as one would normally do) and when focus shift begins, the D850 will automatically start taking shots while moving the focus distance between each shot.
3. This will go on until it goes through all the shots (there is a maximum of 300 shots that can be taken at one go) or until the lens reaches infinity – whichever comes first.
Additionally, interval time between each shot taken can be set from 0 to 30 seconds.
Exposure smoothing and silent photography can also be enabled – with silent photography being perfect for landscape and specimen photography.
It is important to note that not every lens is compatible for use with the focus shift function, a lens with high resolving power be it a zoom lens and/or a macro lens would be most suitable. For example, NIKKOR lenses such as the AF-S NIKKOR 28mm f/1.4E ED, AF-S NIKKOR 105mm f/1.4E ED, AF-S NIKKOR 24-70mm f/2.8E ED VR, and special purpose lens such as the AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED, will work perfectly with focus stacking. Additionally, it is crucial that a steady tripod is used to ensure stability when multiple shots are taken consecutively.
Ultimately, the benefits of focus stacking will show in your photos, especially when it comes to macro and landscape photography. However, achieving good results will take some patience and lots of experimenting since so many variables – subject size, distance from subject, lens choice, aperture setting, and focus step width – are at play.
1 Note: Although this is mentioned, it does not mean that shooting with small aperture is not possible; such aperture settings can still be used when required and if preferred.