I am wanting to purchase a new canon telephoto lens specifically for shooting in poor light conditions indoors with the subjects far away. Can you suggest a good option please?
Without more information, generally, you want to find lenses that are the widest aperture you can get within your budget and matches the focal length you desire. The wider the aperture (lower F#), the more light. Also, shooting at longer focal lengths in low light situations will likely require a tripod or lens with image stabilization.