I am working with Blender principally to render camera animations of photogrammetry models of underwater shipwrecks and other sites. I've successfully animated a camera along a nurbs path, using an empty to change the direction the camera points. So far so good. Where I am struggling is with the camera speed. I wish to initially achieve a steady camera speed along the complete curve, to give a basis for finetuning that camera speed to slow down and speed up along certain segments. However, the initial camera speed that Blender gives me is erratic, and speeds up and slows down seemingly dependent on the acuteness of the curve. It seems to speed up in straighter parts of the curve and slow down when the curve bends more acutely. This is very frustrating and I have to then use the graph editor to try and achieve some semblance of a steady speed, which I an struggling to do. The same speed changes are apparent whether I am using a linear or bezier curve at the start, before applying any other modifiers. I suspect I am missing something pretty basic but I also find it strange that I have not found any other posts on this subject. The attached pic shows the path and areas where the speed up happens
I converted the path to a mesh and back again in order to generate an even distribution of points but that did not make any difference at all. Prior to that I added extra points in between existing ones, also no change.
I am using the "follow path" constraint. I am enabling the "fixed position" option then using the offset factor to try to fine tune the speed. However the speed changes happen when there are no intermediate keyframes, just one at the start with zero offset factor, and one at the end with 1 offset factor.
Thanks in advance John