If I could only afford to buy one light meter it would be a spot meter.
An incident meter reads light falling on the subject. Hold this meter in front of the subject and point the spherical dome toward the camera. A reflective or spot meter reads the light reflected off of the subject and requires an understanding of the Zone System to determine an F Stop. Simply put, a spot meter wants to put everything it reads at ZONE 5 or 18% neutral grey. Any other value requires an exposure compensation to achieve proper exposure. Here’s a very common example: Spot reading faces. Generally speaking, Caucasian faces are Zone 6 or one stop brighter than Zone 5. Since the spot meter sees everything at Zone 5, your reading of that typical face will give you an F stop that is one stop under proper exposure. So after a face reading, always open up one stop to achieve full exposure. For clouds – open up 2 or more stops, for snow on a sunny day – open up 3 or more stops. For Zones 0-4 you must stop down to achieve the proper value as the spot meter brings those darker values UP to Zone 5. DSLR cameras are equipped with reflective metering systems.Return to Musings