Dome port planner

How it works

Choose a dome, a lens and the sensor format, then tick the extension rings. The planner draws the setup to scale and shows where the dome's centre of curvature sits relative to the lens entrance pupil, whether the dome rim or a port's inner tube cuts the FX (green) or DX (red) field, and how close the lens can focus through the dome. "Optimal extension" is the ring length that puts the centre exactly on the pupil. The table lists the three ring combinations with the smallest offset across the zoom range.

Limitations

The geometry is my own setup: a Nikon Z8 in an Aquatica AZ8 housing. Dome radii and positions come from side-view photos and measurements (about ±2–3 mm), entrance pupils from my own measurements or published data. The dome is treated as a thin spherical shell; glass thickness, lens field curvature, shades and the inner diameters of extension rings are not modelled, and fisheye coverage is approximate. Treat the results as a starting point and confirm every setup in the pool.

Dome

Lens

Sensor format

Focal length

Pupil at 17 mm (from Z mount, mm)

Pupil at 28 mm (from Z mount, mm)

Min. focus at 17 mm (from sensor, cm)

Min. focus at 28 mm (from sensor, cm)

Dome outer radius (mm)

Lens and dome data

Aquatica extension rings Sea&Sea adapter 20 mm always fitted

Port seat

Centre of curvature

Offset centre − pupil

Dome rim from pupil

Closest focus outside dome

FX field DX field Dashed: cut by the dome rim or inner tube Entrance pupil Dome centre of curvature Dome outer surface Minimum focus and closest subject

Best three ring combinations for this dome and lens

Aquatica rings	Stack	Centre − pupil at 17 / 28 mm	Rim margin at widest field (FX)	Closest focus 17 / 28 mm	My test

Ranked by the larger centre-to-pupil offset at the two ends of the zoom, with combinations that cut the image corners pushed down. Rim margin: how far the dome rim clears the widest field (Borderline within ±1.5°). Tap a row to load it into the drawing. "Stack" is the Aquatica ring length only; for the 170AR and the Howshot the 20 mm Sea&Sea adapter, and for the Ikelite dome the 9 mm adapter, is added on top.

This planner is provided as is, for information only. I accept no liability for errors or for any consequences of using its results.