Most photo manipulation software, just as Adobe Lightroom, can stitch together multiple images to create an amazing panorama. But if you just rotate your camera on your tripod, you will lose parts of your frames and end up with a less than satisfactory result. By using a macro / nodal rail purchased for about GB£8-10 / US$9-12 you can reduce the problems of stitching images together in post-production.
Why do I need a rail?
If you shoot the same scene from a slightly different point of view, the foreground will be shifted in relation to the background. This occurs when you rotate your camera on your tripod because something called the lens's entrance pupil is moving in relation to the sensor. However, if you rotate your camera around this "no-parallax point" or "nodal point", the shift does not happen. In order to achieve this, you need move your camera's position and the rail allows you to do this.
How do I find the entrance pupil?
Attach the lens that you usually use for landscape photography to your camera. Then mount your camera on the macro rail and ensure it is level. The easiest way is to position your tripod as far away from a wall as possible. At the same height as your camera lens, stick some masking tape where you have made some graduations on the wall (image). About half way between your camera and the wall set up a thin pole so your camera, the pole and the tape are perfectly aligned. You can use a light stand or bamboo stick for this, but it must be thin. Look through the view finder to make sure they are perfectly aligned. Ensure that you have everything in focus in the viewfinder or live view. With the camera right at the back of the rail, turn it left and right. You should notice the pole shifting in relation to the graduated tape.
Now, with the camera slightly turned so that the pole is slightly offset, adjust the rail until the moment when the poles and the centre of the tape become aligned. Turn the camera from side to side again, and adjust as necessary. This can be really fiddly, but you will have found the entrance pupil.
Mark the camera's position on the rail with a permanent marker and you have calibrated your lens. You are now good to go every time you're out in the field.
Buying a proper nodal rail can be expensive. If, like me, you don't take many landscapes, this is a cheap and effective hack. And you will obtain much better results when you stitch your images together in whichever software you use.
The downside is that the rail only works in a landscape and not in a portrait position. So although this is limiting, I strongly recommend giving it a go.