It's arguably the biggest problem in macro photography: you get close to your subject and typically select a wide aperture to capture as much light as possible, but as a result the depth of field becomes very narrow, leaving much of your image out of focus. Whether you're shooting macro images of tiny insects or a wide expanse of landscape, sometimes you crave a greater depth of field than one shot with one lens can provide. Simply closing down to a small aperture may not give enough sharpness throughout the frame, particularly when shooting macro. That's where focus stacking can help.
To create focus-stacked images, you start by bracketing a number of images of the same subject with slightly different parts of that subject in focus. Those images are then blended together, or 'stacked', in post-production to produce a single image that has greater depth of field, with the subject in focus throughout the frame. It's a great way to transcend a lens's natural limits and create images that are extraordinarily sharp and detailed throughout.
But how exactly do you take and blend focus-stacked images successfully? How does the technique differ when shooting landscapes rather than macro, what is the best kit to use, and how do you turn a succession of shots into one detailed image? Here, Canon Ambassador and nature photojournalist Christian Ziegler, macro specialist Matt Doogue and landscape and travel photographer David Clapp share how they use focus stacking to create detail-rich shots.
Matt Doogue began photographing insects and arachnids seven years ago. He has refined his focus stacking technique to overcome extremely narrow depth of field while shooting small subjects at high magnification. He typically uses a Canon EOS 6D (now succeeded by the Canon EOS 6D Mark II) paired with a Canon MP-E 65mm f/2.8 1-5x Macro or Canon EF 100mm f/2.8L Macro IS USM lens, for their wide apertures and magnification factor.
"Most people think that by using very small apertures you'll get more of the subject in focus," he says. "That's correct, but that's also going to cause diffraction, where light disperses and image sharpness is reduced, and your exposures are much longer.
"Shooting at wide apertures such as f/2.8 avoids diffraction and allows me to let more light in, so I can use shorter exposures. However, if I'm shooting a spider at 5x magnification on my 65mm macro lens, I will get only the two front eyes in focus and the rest is completely blurred. Focus stacking allows me to bring that whole face in focus to get an amazing portrait."
Because he is photographing living, moving subjects, Matt often has to work quickly to take more than one image of a subject at slightly different focus points. To do this, for almost all his work Matt shoots with the camera handheld, which allows him more freedom of movement. Rather than moving the focusing ring on the lens, which would also change the magnification on a macro lens, he moves the camera back and forward while shooting.
How many shots Matt takes of a subject partly depends on the level of magnification at which he's working. For example, if he's shooting at 1x magnification he will need three or four images to stack to get the whole subject sharp, but at 2x magnification he needs eight shots, and so on.
The number of shots partly depends on how many he can shoot before the subject moves. "Jumping spiders, for example, move frequently, so I'll be happy to get two or three shots," he explains. "With subjects such as beetles or spiders on the web, I'll always try to get a minimum of eight shots. But the more you can get with different focus points, the better, because the more shots you have, the greater the depth of field in the final image."
Christian Ziegler recently used the focus stacking technique for a series of images of flowers and plants, taken in Scotland on his Canon EOS-1D X Mark III with a Canon EF 100mm f/2.8L Macro IS USM lens.
"I rediscovered focus stacking during the Covid-19 lockdown, while we have all been stuck at home," he says. "I used this technique maybe 15 years ago in Panama for flowers, but it was much more complicated back then. Now, post-processing is so simple that it's easy to take some images, play around and see if it works.
"I spent a lot of time documenting the onset of spring. I especially love spring flowers and young leaves. I collected many species and brought them back to my studio to play around with them – taking multiple images and then stacking them to create a perfectly sharp image. I think this technique works really well for natural details such as flowers, seed heads and insects. I wanted to show the beauty and delicate nature of these subjects."
While Matt has developed his technique to capture enough detail of his moving subjects before they change position, Christian is able to take time with his still subjects to capture every nanometre of detail. He brings flowers such as poppies and bluebells, as well as plants such as ferns and nettles, into his studio. This allows him to control the light exactly, and to avoid the problem of wind moving his subjects during and between exposures. He typically shoots between four and 17 exposures to capture subjects in focus from the nearest to the furthest point, ensuring every trichome (plant hair) and marking is in sharp focus.
Christian tripod-mounts his camera for perfect stability, then shoots the flowers against a black background to draw attention to their shape, textures and colours. The Canon EF 100mm f/2.8L Macro IS USM is the ideal choice for focus stacked plant images because "it's really sharp," he says.
When shooting static subjects in an indoor environment, Christian says if you are methodical in your approach, good results will follow. "I don't think you can really go wrong with this technique," he continues. "I encourage people to try out multiple different subjects – close-ups of plants, fungi or insects work really well. I would say the only mistakes I have made are trying to take images outside on a stormy day – this didn't work! You really need the subject to be still."
Focus stacking is also a useful technique in landscape photography. Landscape and travel specialist David Clapp has been using it for over 10 years to create images with sharp focus from foreground to background.
He uses it mainly when extending depth of field beyond the capability of the lens he's using, particularly telephoto lenses. He also uses it when he's photographing in low light and finds it's not possible to shoot with a fast enough shutter speed to avoid subject movement while keeping all the required elements in focus.
David shoots with the Canon EOS 5D Mark IV and lenses including the Canon EF 24-70mm f/4L IS USM and the Canon EF 100-400mm f/4.5-5.6L IS USM (now succeeded by the Canon EF 100-400mm f/4.5-5.6L IS II USM). Using manual focus, he starts with the lens focused at infinity and gradually changes his focus point until it reaches the nearest part of the foreground. His camera is always tripod-mounted.
"If you're shooting with wide-angle lenses and small apertures, you'll have a lot of native depth of field, so you won't need to take so many pictures to get a sharp image throughout," he explains. "However, the longer the focal length, the more you have to be careful about how you stack an image together. If you're working in low light, the adjustments in focus between each frame will be very small, because the aperture will be bigger and therefore the depth of field on each frame smaller. The focus stacker's worst nightmare is having a sliver of the scene out of focus between two images."
When capturing focus stacking landscape shots, he says, there are several things to bear in mind. "If you're working on softer surfaces such as sand, every time you handle the camera you'll move the position of the tripod very slightly. You have to make sure it's firmly embedded into the ground and doesn't move. Also, you have to shoot using manual exposure as using an automatic mode can result in the camera altering the exposure or white balance between frames, which creates complications at the post-processing stage."
Some Canon cameras such as the Canon EOS R5, Canon EOS R6, Canon EOS RP and Canon EOS 90D feature built-in automatic focus bracketing, to make capturing your focus stacking images even easier. This enables you to set the camera to shoot the desired number of images at selected focusing increments. The camera starts focus bracketing from the nearest point and works towards infinity. The wider the aperture, the more gradual the focus increments and the greater the number of shots.
Once they've captured their component images, the three photographers have different ways of creating their final stacked images, using either general image editing software or dedicated focus stacking programs. However, their post-capture process is broadly similar: the shots that give the widest range of focal points are selected and edited; then, they are aligned and blended into one composite image, with any anomalies removed (such as an insect's leg that has moved between exposures in Matt's work).
Canon's Digital Photo Professional (DPP) software, a free download for owners of Canon EOS cameras, is the perfect tool. Version 4.10 and newer include a Depth Compositing function, which is compatible with images taken with cameras that feature focus bracketing along with the Canon EOS R, Canon EOS RP and Canon EOS 5D Mark IV. This function enables images to be automatically adjusted in certain ways, for example smoothing the compositing boundary. The output image can be adjusted using the Depth Compositing Editing tool to ultimately produce a single perfectly focused image.