Focus stacking how to achieve pin sharp macro shots

Geraint is an Olympus ambassador with a love for macro photography. He hopes that his images may inspire others to care for insects.

Macro photography lets us explore the magical world of mini beasts, flora and fauna. I love to photograph live wild insects, yet discourage the use of any practices that could these tiny important beings. When working close to our subjects, the depth of field reduces considerably. The smaller apertures needed to achieve extra depth of field can impact picture quality through diffraction and reduce the faster shutter speeds we need to maintain image sharpness.

What is focus stacking?

Focus stacking is a great solution to this dilemma. Using this technique, we can shoot a sequence of images at different focusing distances and use software to the sharp areas together into a single file with greater depth of field and better image quality.

By focus stacking, we can use wider apertures with lower numbers to maintain a decent shutter speed. Sounds perfect, but there are a few caveats. For a successful stack, exposure must be consistent and neither we nor the subject can move. Photographing living beings means we won’t have the opportunity to shoot hundreds of frames. The keep rate can be low, but thankfully there are some things we can do that will increase our odds of success.

Dawn and dusk are ideal shooting times as the cooler temperatures make creatures easier to approach and they’re less likely to move. Stability is key to successful stacking. My camera has seven stops of in-camera stability, enabling me to shoot handheld. A ground-level tripod may be useful, while a centre column that tilts horizontally will stop the tripod legs from getting in your way. Diffused flash will give us complete control of our lighting and help reduce camera shake, especially when shooting handheld. My flash and 30cm diffuser is mounted directly above my lens pointing downwards to achieve soft lighting and nice shadows. This also avoids the light shining directly into the eyes of my subjects.

Geraint’s focus stacking kit list

Macro lens

Macro lenses are my favourite invention! Being designed especially for close-up work, they will achieve 1:1 magnification. The longer the focal length, the further from our subject we can be and still achieve maximum magnification. I would recommend at least 90mm for insect photography.

Extension tubes

These work by increasing the distance between the lens and the camera sensor, so we can focus much closer. The downside is that working distance is reduced, and this in turn reduces the depth of field. Ambient light is also lessened, so a combination of artificial light and focus stacking will give great results.

Flash and diffuser

A great flashgun with a speedy recycling time will be your best friend when shooting macro images handheld. Good diffusion will help with controlling the highlights created by the shiny exoskeletons of our buddies.

The depth of field is very shallow and we need more to show this beautiful creature in all its glory. With two sets of extension tubes attached to my 60mm (120mm full-frame equivalent) macro lens, an aperture of f/5.6 is the limit before diffraction sets in. Focusing is achieved manually by composing the shot and then moving the camera towards the subject. Make small adjustments to ensure each image overlaps properly. Using the rule of thirds grid in our view finder helps visual alignment. Use them as crosshairs to make sure the focal point remains the same in each picture.

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