Panoramic heads: how they work and how to find the no-parallax point

A panoramic head turns your camera around the no-parallax point of the lens instead of around the tripod screw. Rotated about that point, near and far objects keep the same position relative to each other from shot to shot, so stitching software can join the photos without ghosting or broken lines.

Nodal point or no-parallax point?

Panorama photographers usually call this point the "nodal point". The PanoTools wiki and the Hugin manual both point out that this is wrong: the point you need is the centre of the lens's entrance pupil, the image of the aperture seen through the front of the lens. A lens's actual nodal points are different points on the optical path. The no-parallax point can even move slightly when you change the aperture, which is one reason to set a head up at the aperture you will shoot at.

Types of panoramic head

• Single-row heads turn horizontally only. They are enough for a cylindrical panorama, such as a skyline.
• Multi-row (spherical) heads add a vertical arm and a second rotator, so you can shoot rows above and below the horizon and cover a full sphere. Manfrotto's 303SPH is one.
• Fisheye ring heads clamp around one specific fisheye lens and hold it at its no-parallax point, so a full sphere takes only a few frames.
• Small travel heads for compact cameras and light mirrorless bodies weigh far less than a full multi-row head, and give a small camera a fixed rotation point on a tripod.
• Gigapixel heads have finer click stops, a few degrees apart, for shooting many narrow telephoto frames.
• Motorized heads do the turning and triggering for you. See motorized panoramic heads.

A different route skips the head altogether: one-shot 360° cameras such as the Insta360 X5 record the whole sphere at once through two back-to-back fisheye lenses and stitch it in software. They trade the resolution and control of a head-and-camera setup for speed.

Most heads have click stops on the rotator, detents at fixed angles such as 15° or 30°, so each shot overlaps the last by the same amount. The wider the lens, the bigger the step can be.

How many shots: overlap and step

Neighbouring frames need to overlap so the stitching software can find the same features in both. A 25 to 30 percent overlap is the usual minimum; PTGui users put the ideal at 25 to 33 percent.

Each shot then advances by the lens's horizontal angle of view minus the overlap, so:

shots per row = 360° ÷ (horizontal angle of view × (1 − overlap))

A lens that covers 60° across, at 30 percent overlap, advances 42° per shot: nine shots for a full row. The angle of view follows from the sensor size and focal length, 2 × arctan(sensor width ÷ (2 × focal length)). A 24mm lens on a full-frame camera covers about 74° across with the camera held horizontally, and 53° with it turned upright. Turning the camera upright needs more shots per row but covers more height in each.

Setting a head up

1. Centre the lens over the vertical axis. Seen from the front, the lens should sit directly over the rotator. Many heads have a scale for the side-to-side offset.
2. Find the front-to-back position. Line up a near object, such as a pole, with a far one, such as a door frame. Turn the head left and right. If the two drift apart, slide the camera forward or back on the rail and try again until they stay together.
3. Note the setting for that lens, zoom position and aperture, so you can set it again next time without repeating the test.

Photography Life's panorama tips cover the same test with a nodal slide.

Level the base first

The rotation axis must be vertical. If the tripod is not level, the horizon rises and falls across the panorama, and the stitching software has to correct the resulting "wavy" image. A spirit level on the tripod, or a separate levelling base under the head, fixes this before you shoot. Some heads come with one, such as Really Right Stuff's PG-01 pano-gimbal kit.

What you get: projections

• Cylindrical: a single wide strip, for one row around the horizon.
• Spherical (equirectangular): the whole sphere, 360° across and 180° from top to bottom, flattened into one image exactly twice as wide as it is tall (2:1). Viewing software generally assumes this 2:1 shape for a full sphere: Google Maps asks for a 2:1 aspect ratio and at least 7.5 megapixels for uploaded photo spheres, and 360Cities asks for the same ratio. Free web viewers such as Pannellum and Marzipano display it directly.
• Cubic: the sphere as six square faces, used as input by some spherical viewers.

Cambridge in Colour's guide to panoramic projections shows how each one bends straight lines.

The tripod in the picture: the nadir

The nadir is the point directly below the camera, so in a full sphere the tripod and head are in the picture. Common fixes are to mask the tripod out of the overlapping shots in the stitching software, to take an extra hand-held shot of the ground with the tripod moved aside and blend it in, or to cover the spot with a small round patch, often a logo. The point straight above is the zenith.

Stitching software

• Hugin is free and open source (GPL), for Linux, macOS and Windows. It finds control points, the matching features in neighbouring images, and uses them to align and blend the shots.
• PTGui is commercial software for Windows and macOS, first released in 2001, and handles both telephoto rows and fisheye spheres. Its Pro version adds masking for problems such as the tripod in the nadir.

Both began as graphical front ends to Panorama Tools, the stitching library written by Helmut Dersch. For simpler jobs, Lightroom Classic can merge photos into a panorama with spherical, cylindrical or perspective projection.

Where to buy one

Current makers of manual panoramic heads include Nodal Ninja and Novoflex. For 360° product photos, the camera stays still and the object turns instead: see turntables.