Updated · 3 min read
Macro is where focus stacking earns its keep. At life size, a single frame holds well under a millimetre of sharpness at wide apertures. Stack the right series, though, and an entire insect can be sharp from antennae to wingtips.
How thin the sharp zone really is
| Magnification | f/4 | f/8 | f/11 |
|---|---|---|---|
| 0.5× (half life size) | 1.4 mm | 2.9 mm | 4.0 mm |
| 1× (life size) | 0.48 mm | 0.96 mm | 1.3 mm |
| 2× | 0.18 mm | 0.36 mm | 0.50 mm |
| 5× | 0.06 mm | 0.12 mm | 0.16 mm |
A 10 mm deep beetle at 1:1 and f/8 needs roughly 15 frames. At 2× it needs around 40, and at 5× well over a hundred. That’s why the stacking method matters more in macro than anywhere else.
Gear
- Macro lens. A true 1:1 macro lens is the simplest start. Extension tubes, close-up lenses and microscope objectives go further.
- Tripod or copy stand. Rigid, with a head that doesn’t creep. Vibration matters at high magnification.
- Focusing rail. Moves the whole camera in fine steps instead of turning the focus ring. Motorised rails (StackShot, WeMacro and similar) automate long series.
- Light. One or two flashes with a large diffuser, or LED panels for still subjects.
- Remote release. Or the camera’s self-timer, to avoid touching the camera.
Focus ring or rail?
Turning the focus (by hand or with the camera’s focus bracketing) is quick and works with autofocus lenses. The image size changes as focus moves, and good software corrects that, but the edges of the frame get cropped. A rail keeps magnification constant and gives much finer steps, which is why it’s standard beyond 1:1.
Shooting technique
Set the magnification first
Frame the subject, then leave the lens alone if you’re stacking with a rail.
Pick the aperture
f/5.6–f/8 on full frame is a good balance. Beyond 2×, open up further: diffraction softens the image more than the extra depth helps.
Find the near and far points
Note where the nearest and furthest parts of the subject come into focus. Start a frame or two before the nearest, end a frame or two after the furthest.
Choose the step
About two-thirds of the depth of field per frame, so neighbouring frames overlap. See step size and aperture.
Keep the light steady
Same flash power for every frame, or constant light. Varying light causes stripes in the stack.
Live insects
Live subjects allow only a few seconds. Shoot short bursts of 5–20 frames, handheld with flash, rocking gently forward or using the camera’s fastest bracketing. Early morning, when insects are cool and still, is the best time. Never chill or harm an animal to make it hold still. Some movement is unavoidable: legs and antennae shift between frames. Software that points out where something moved, and lets you paint that spot in from one frame, saves a lot of these shots. See focus stacking artifacts.
Questions
- What aperture is best for macro focus stacking?
- Around f/5.6 to f/8 on full frame at 1:1. At higher magnification, open up: the effective aperture is smaller than the number on the lens, and diffraction blur grows.
- How many photos do I need for a macro stack?
- Divide the subject’s depth by about two-thirds of the depth of field per frame. A 10 mm subject at 1:1 and f/8 needs about 15 frames; at 2× about 40.
- Do I need a focusing rail?
- Not up to about life size; focus bracketing in the camera works well. Above 1:1, a rail gives finer, more even steps and keeps the magnification constant.