You should rent a camera lens when the lens or lenses you have won’t work for that you are trying to photograph. This is a simple statement but there’s usually an emotional barrier that keeps us from making this decision. Often it feels like a financial restraint, because we don’t want to spend money on something we don’t get to keep. This is a healthy reaction to have, to prevent us unnecessary spending. The key word here is ‘unnecessary.’  You may reason that it is unnecessary to rent a lens when you don’t have a good reason for it. But renting a lens is a great option when buying a lens would be unnecessary. So, it’s a great idea to rent a lens if you only need a lens for a short time; like one trip or one photoshoot. Or if you need a lens for a particular type of shot you are trying to get. In that case, having the right gear for the job becomes a good financial decision and will save you a lot of time and effort.