So in the last post we touched on the importance of keeping a steady head when shooting 360 images. This nugget of information is all about keeping on point, literally.
So what is parallax? If you want the proper explanation, go here. However for a contextual explanation, read on.
What is it then?
In terms of taking a 360 picture, parallax is the perspective offset of objects in the camera’s frame induced by the rotation of the camera on the tripod. To achieve a clean stitch in whatever processing software you use – PTGui for example – you need to minimise the parallax so when the software is analysing the pictures it can match up different objects in different pictures accurately – control points – and produce a lovely clean image.
Getting to the Point
To do this the camera needs to be set up at what is known as the Nodal Point. This is the point inside the lens where the light beams converge to a single point. Most lens manufacturers do not supply this information so you, and by you we mean we, have to go through a process of trial & error to arrive at a suitable close approximation.
How to mitigate?
To position the lens at the nodal point we need to move it in the three axes, X, Y, Z. To do this we use something like this:
Looks nice and complicated but it’s really 3 lockable slides that allow you to position the lens correctly before rotation to capture the photosphere.
To help reduce the risk of introducing unnecessary parallax into the stitching process it is good practice to use as wide a lens as possible so fewer exposures are needed to complete the photosphere and less stitching is required knitting the exposures together. For this a fisheye lens is a good thing to have in your arsenal.
For the avoidance of doubt, it’s the one on the right you need. In this instance.
The setup process takes time, hence the lax in the title, and it is time that, as a company, we invest independent of customer jobs. But it is time well spent ensuring the pictures produced are of the highest image quality.
Of course if you use multi lens static camera rigs, and we do too, then parallax is generally not a problem however they cannot yet match the picture quality of a DSLR.