Focus Stacking Shot Count Calculator

Focus stacking is a technique where you take multiple photos at different focus distances and merge them in software to achieve sharpness across a depth that exceeds what any single lens aperture can deliver.

It is essential for macro photography (extreme close-ups of insects, flowers, coins, food) where depth of field can be less than 1 mm at high magnification.

Depth of field (DoF) per frame

The shortcut you see everywhere is DoF ≈ 2 × N × c × u² / f², and it is fine for a portrait at ten feet. It is not fine here. At 1:1 magnification it reports twice the depth of field you actually have, which means twice the step size and half the frames, and a stack with focus gaps in it.

This page uses the exact form instead, the same one the depth-of-field calculator uses:

H = f² / (N × c) + f
near = (H × u) / (H + u − f)
far  = (H × u) / (H − u + f)
DoF  = far − near

Where:

• N = aperture f-number
• c = circle of confusion (sensor-dependent)
• u = focus distance from the lens
• f = focal length
• H = hyperfocal distance

At macro distances the equivalent shorthand is DoF = 2 × N × c × (1 + m) / m², where m is magnification, m = f / (u − f). Both give the same answer. A 100 mm lens at f/8 focused 200 mm away is at 1:1, and the honest figure there is 0.96 mm, not the 1.92 mm the popular approximation returns.

Circle of confusion by sensor size:

• Full frame (35mm): 0.030 mm
• APS-C (Canon): 0.019 mm
• APS-C (Nikon/Sony): 0.020 mm
• Micro Four Thirds: 0.015 mm

Number of shots needed: Shots = Subject Depth / (DoF per shot × overlap factor)

Using 20–30% overlap between frames ensures no focus gap in the final merge.

Practical steps:

1. Set your camera to aperture priority or manual
2. Use f/5.6–f/11 for macro (avoid diffraction at f/16+)
3. Use a focusing rail for precise incremental focus shifts
4. Shoot in RAW for best merge quality
5. Use Helicon Focus, Zerene Stacker, or Photoshop’s Auto-Blend Layers

Recommended apertures for stacking:

• Macro (1:1): f/5.6–f/8 for sharpest optical quality
• Close-up (1:3–1:5): f/8–f/11
• Product photography: f/8–f/16
• Avoid f/22 and smaller, where diffraction softens images significantly

Software options:

• Helicon Focus (paid, excellent for macro)
• Zerene Stacker (paid, great for insects)
• Adobe Photoshop (Edit → Auto-Blend Layers → Stack Images)
• Affinity Photo, which handles moderate stacks well and costs a fraction of the dedicated tools