Spherical panoramas are often known as 360° images, which allow the user to become fully immersed within an image. These are the sort of images you see on Facebook that allow you to move the device around and see all aspects of the image.
Typically these images are captured in two different ways, the first is using a ready made device which consists of multiple lenses to cover a 360 degree field of view horizontally and an 180 degree field of view vertically (e.g. Ricoh Theta S, Samsung Gear 360). The second way to capture these images is to take individual images with overlap between each and stitch them into one overall equirectantular image using software (e.g. KRPano, Autopano Giga).
Typically to conduct 360 images, I use a NIkkor 10.5mm fisheye lense which is designed for APS-C (DX) Nikon bodies. In my case I normally use the D5300, or occasionally I use it on a full-frame body (the D610) and accept a lower resolution due to cropping. The camera is positioned in portrait mode.
The 10.5mm DX lens has a field of fiew of around 140 degrees (horizontal), 87 degrees (vertical) and a diagional field of view just shy of 180 degrees. Based on these figures, if I am aiming for around 30% overlap (this is about ideal) then I typically need a total of eight (8) images, six (6) across the horizontal every 60 degrees, one towards the sky (zenith) and one towards the floor (nadir).
The important thing with these types of images is to find the nodal point for this lens. This is not the same for all lenses,
Moving in 60 Degree Increments:
Some tripods have a degree indicator which is fairly useful to determine how far you need to move in order to equally move 60 degrees each interval, e.g. 0, 60, 120 degrees and so on. However, at night this can be somewhat difficuilt which is why I use an Indexing Rotator.
The indexing rotator is basically a rotating head which has a screw that is screwed into the side of the device, within the head there are small indents based on the number of degrees moved, so when you attach the screw to the 5 degrees per stop hole, along that horizontal path there are holes every 5 degrees which means the device sort of “Clicks” when it gets to the right point. It is not a loud noise, but you can feel it as it moves which is great when it is dark.
Depending on which model is purchased, the rotator allows intervals to be set of 5, 10, 15, 20, 24, 30, 36, 45, 60 and 90 degrees. In my case I use the 60 degrees per stop.
The Nodal point:
In order to avoid paralax issues, it is important to find the nodal point for the specific lens you are using. A full explaination of the nodal point is outside of the scope of this article, but can be found at huga.co.uk, but basically the nodal point is considered to the the point where all of the rays entering the lens converge.
For the Nikkor 10.5mm lens, without the hood shaved the nodal point is approximatally 46mm from the camera mount of the 10.5mm lens.
The reason the nodal point is important is because we need the camera to rotate around that point, this means that when we mount the camera and lense on the tripod, it needs to rotate on that nodal point (e.g. 46mm from the camera mount of the lens), not the tripod mount of the camera. Failing to do this will lead to paralax issues and likely poor stitching…
There are nodal mounts that exist, or a pipe clamp like device called the Nodal Ninja Lens Ring, which should assist with this mounting.
Once we have the gear ready, and we have found our position we are JUST about ready to start taking pictures. The best way to achieve optimal results is to move to manual mode and set your ISO, shutter speed and aperture to an appropiate setting based on your entire scene. This is really important as it avoids exposure based stitching issues.
Once the settings are determined, start capturing :), then get ready to process the images (which will be explained in a future post) :).