Figure 1. Photo taken at 16mm. Click to Enlarge

There is a discussion happening on the Bushwalking Tasmania about how to take good panorama images. At the request of one of the forum members, I am writing a little bit about why the focal length is important when composing your panorama shot. When I take panorama images, I always use a 50mm lens of greater.

What most people seem to forget with cameras is that you are taking an image from the lens that is circular, and you are putting it on a rectilinear sensor or film. as your angle of vision increases (usually at smaller focal lengths), the more likely you are to experience Barrel Distortion, particularly with fisheye lenses. Barrel Distortion will cause you problems when you start stitching together your panorama.

Figure 1 was taken with a Sigma 10-20mm Lens, at 10mm. Taking into account the Canon crop factor of 1.6 on APS-C Sensor, it works out to 16mm. Here you can see that the stitching tool is showing you how much distortion it needs to crop from the image to make it a panorama, and you will also note that there is still significant distortion on the vertical edges resulting in obvious stitching joins. You can also see that you lose some 30-40% of the image’s height due to the crop.

Figure 2. Taken with Canon 50mm f1.8. Click to enlarge.

Figure 2 is taken with a Canon 50mm prime lens (80mm after crop factor). You can immediately see in this photo that less than 5% of the image’s height is lost in cropping. It is also distinctly harder to spot the joins in the image  because there is so little barrel distortion.

From these 2 examples, you can quickly see why I only take panoramas with normal lenses, as opposed to wide & ultrawide. Why 50mm? It seems to be a sweet spot, and thats what other photographers have said to use. you could probably use more telephoto lenses if you wanted to, but it would defeat the purpose.

One last tip – don’t forget you can “cheat” and crop a picture into a panorama (Figure 3). With most digital cameras sporting sensors capable of over 7 megapixels, shooting at a ultrawide angle and then cropping the image in post may be an effective compromise. Be aware though that this technique will only be suitable for computer screen and small prints. Stitching of multiple images is the way to go if you want large prints.

Figure 3. Fake Panorama. Cropped in Post. Click to Enlarge