Originally posted by mikemike I have often read that extra mm are more important on the wide end or are more substantial than on telephoto but I don't really see why.
I made a spreadsheet that calculates the angular field of view and the distance from subject required to have a 2 m field of view (i.e. taking a head to toe picture of an adult) and it is perfectly linear so I don't see why other than if you are backed up to a wall or pressed up to the edge of a cliff or guard rail.
Attachment 205396 There are two aspects to this.
First of all, and I have found this over years of travelling in Europe , you simply can't back up the 5-10 meters needed to use a longer lens. Consider a narrow street in an old town. Likely it will be in the range of 3-6 meters side to side. Even the field of view of a 14-15mm lens is not enough to fit that magnificent church you want to photograph into the scene.
On the long end, you can always crop, and further reduce the FOV, but you can't ever increase it.