Some panoramas look sharper than others.
If two panoramas are represented in the same format, we can simply compare the number of pixels in their respective images in order to compare the resolution of the panoramas. The matter is not quite so simple if the panoramas are represented in different formats. This is a meaningless number, because the dpi can be changed to an arbitrary number without changing the number of pixels in the image, yet the image still retains its sharpness and field of view. First, we need to define what we mean by angular pixel density, because no image format is uniform in angular pixel density across the whole image. We use the focal length as the basis of the definition.