I use the L358 when i'm in controlled situations... In camera meters only measures reflected light which bounces off your subject to the camera... It does an OK job but gets a lot of flack when it doesn't "nail" exposure. Most external light meters no matter the brand gives you the option to measure reflective as well as incident light (the actual light that hits your subject... It gives you a good base of A) how each light is affecting your subject, brightness, and gives you good control, and B) allows you to measure each light individually and everything cumulative by aiming the dome back to the camera. You just really dont get that control in metering with a reflective meter which you dont get with reflective meters... Reflective meters are good if you know how to read it, know how it relates to the scene and compensate depending on what it gives you (+2 stops if metering white subjects, -2 if measuring dark subjects, etc....)