Edit: I didn't make this clear, for this is for the possible future development of an application.
I am looking into individual facial recognition for an application, but an essential part of this seems to be a fairly large training set of images for each individual to be recognized.
Is it important for the images to be taken at different times in different environments, or could several images captured over a few seconds with a handheld camera possibly provide the necessary variations for a good training set?
(This isn't for human facial recognition, by the way, so existing tools and databases won't really help too much. I'm aware that 2D image recognition can not necessarily be applied to all species; let's just assume that it does work in my use case.)