360 Panoramic Photography ~ First Principles
So you have spent some big bucks and are now looking to produce your first pano. With all this fancy equipment and software you cannot go wrong, right?
Wrong! Get ready for some head scratching, hair pulling, brow wiping and generally frustrating times ahead. As with photography in general it is 90 per cent experimentation and learning from your mistakes. There are some golden rules to follow of course but these are not going to guarantee you great or even good results to begin with. Please do not think at this point that I am trying to put you off, of course I am not, but anyone that tries to run before they can walk is always going to end up flat on their face! So take your time, have some fun and be patient. With practise and experience you will steadily improve and start to produce some nice looking panos.
Golden Rule Number 1
Your camera/pano-head settings must be spot on.
In order to successfully stitch photographs together, the images must all have been taken from the same viewpoint and perspective. This can only be achieved by rotating the camera about the lens point of no parallax. This point is often incorrectly referred to as the Nodal Point of the lens; however nodal point means something quite different (which is another story). If the camera is not rotated about this point then there will be parallax errors and it will be very difficult or impossible to stitch the images successfully, depending upon the amount of parallax.
So what is parallax? The Oxford English Dictionary describes it as the apparent difference in the position of an object when viewed from different positions. The easiest way to illustrate parallax is to stand on a spot, close one eye, look straight ahead at a distant object and then hold your index finger straight up about ten inches in front of your eye. Note where the object is in relation to your finger and then rotate your head a few degrees whilst holding your finger in the same place. Notice how the object moves in relation to your finger. This is because your head is not rotating about the point of no parallax, which in this instance would be the point at which the light enters your eye. The same thing occurs when a camera is rotated on a conventional tripod head. Objects far away from the camera will move in relation to objects that are much nearer. Stitching a sequence of images together where this has occurred is simply not going to produce good results. Your software may still link the images together but there will be obvious stitching errors and the finished pano will be flawed. To overcome this problem we rotate the camera about the lens point of no parallax.
The next question you are asking is probably how do I find the lenss PNP (point of no parallax)? My advice would be not to bother. Simply refer to the settings table (hopefully) provided by the manufacturer of your panoramic head. If this does not come with the pano head itself, it should be available on their website. Nodal Ninja provide one on their website here. This will save you a lot of time and effort chasing your tail. I have spent hours and hours trying to find PNPs on my lenses and in the end always ended up referring back to the table anyway. Without trying to confuse the issue, one should be aware that a fisheye lens does not have a set PNP anyway as the light enters the lens at different points depending on the angle of entry. (The light from an object 150 degrees to the lens enters at a different point to the light from an object directly ahead, this is how a fisheye lens works). Therefore the settings for a fisheye lens will minimise parallax but not completely eliminate it. Despite this, a high percentage of virtual tours and panos are created using fisheye lenses!
So to summarise Golden Rule number 1, find the correct settings and always make sure that your camera, lens and pano-head are set up perfectly. It will save you a big headache later on!
Golden Rule Number 2
The tripod and set-up must be rock steady. If anything moves during the shoot, even slightly, you must start again. Need I say more?
Golden Rule Number 3
The pano-head should be level. Many panoramic heads have bubble levels built in which makes life easier. An 'Easy Leveller' is not a necessity but it will save fiddling around with the tripod for ages trying to get it level. Most of the panoramic head manufacturers produce these levellers. If you remember and always stick to these golden rules then you will arrive back at your computer, after a shoot, in pretty good shape each time. There are no guarantees of course, and you will make mistakes to begin with. Photography can never be a robotic procedure that gets automatic perfect results but you can build yourself a solid base to work from.
