Dome Port Calculation

How it works

Choose a dome, a lens and the sensor format, then tick the extension rings. A dome port works best when the centre of curvature of the dome sits exactly on the entrance pupil of the lens. The planner 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 of view, 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 below the drawing 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.

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