Depth of Field in Macro Photography: Aperture Choice and Focus Stacking

The biggest challenge in macro photography isn’t choosing the aperture — it’s accepting how truly thin the depth of field really is at 1:1 magnification. In this article we cover both the aperture range that gives the best result in a single frame and focus stacking, the only real way to render the whole frame sharp.

Aperture: the f/8–f/11 sweet spot

At 1:1 magnification, the same aperture produces a far thinner depth of field than in a normal shot. If you stop down to f/11 and shoot a subject 20 cm away, the sharp area may be only 2–3 millimetres. Stopping down hard (f/16–f/22) increases depth of field, but image sharpness drops because of diffraction — often the overall sharpness at f/22 comes out worse than at f/11. So for single-frame shots, the f/8–f/11 range strikes the best balance between lens performance and usable depth of field.

Shutter and ISO: reserve the light for aperture

Because you keep the aperture narrow, less light enters; to compensate, rather than lowering the shutter (camera-shake risk) prefer first raising ISO, and if needed adding an external flash or ring light. If you use a tripod, 1/60–1/125s is enough; handheld, for moving subjects like a flower swaying in the wind, 1/250s and up is safe.

What is focus stacking, and when is it needed?

Focus stacking is a technique for achieving a depth of field wider than a single frame can give, by combining multiple frames shot at different focus points into a single image. When you want to render a static subject (a dried insect, jewellery, a product shot) sharp from front to back, you shoot 5 to 50+ frames, each focused a little farther, then blend them in software.

Shooting technique

• Fix the camera to a sturdy tripod or a focusing rail.
• Set exposure, white balance and focus to manual — no setting should change automatically between frames.
• Advance the focusing rail in fixed increments. The focus planes of consecutive frames should overlap by about 1/3 of the depth of field at that magnification. At a 2mm depth of field, steps of 0.5–0.7mm are appropriate.

Blending software

Helicon Focus and Zerene Stacker are the industry-standard programs for macro focus stacking. For simpler stacks, Adobe Photoshop’s Auto-Align/Auto-Blend feature (Edit > Auto-Blend Layers > Stack Images) does the job.

Be realistic about moving subjects

A flower swaying in the wind or an insect that might flee is not suitable for focus stacking — if the subject moves between frames, the blend fails. In that case, settling for a single frame and focusing on the most important part of the subject (the insect’s eye, the flower’s center) at f/8–f/11 gives the most reliable result.

Common mistakes

• Stopping down to f/22: because of diffraction the image comes out less sharp than expected; try f/8–f/11.
• Trying focus stacking handheld: even the slightest camera shake ruins the alignment between frames; a tripod is essential.
• Focusing on the center of the subject rather than its eye/heart: the viewer’s gaze goes first to the sharpest point, and choosing it correctly is half the composition.