When you first start shooting film, you hear people talking about rating and metering. What exactly are rating and metering? Are they the same or are they different? Rating is when you enter the film speed into your handheld meter for the light exposure calculation. You are "rating" a film stock at 400 when you enter 400 as the ISO on the light meter. For example, when you input 400 as ISO on your meter for Portra 400, you are saying "I rate Portra 400 at 400". Besides rating your film at the speed indicated by the film stock, you can alo rate it at a faster or slower speed than it is indicated on the box. For example, you can rate a Fuji 400h as if it's a 200 speed film by enter 200 as the ISO.
Metering is the actual method you use the light meter to measure the light, either through incident metering mode or reflected metering mode. Besides different metering modes such as incident, evaluative, center weighted, spot metering, you can also tailor how and where to meter for the light to fit your vision and style. Often times, I find myself use a combination of different metering modes and rating to create the style and vision I am after.
As you can see rating and metering have distinctive differences, so it is crucial not to confuse them as the same. If you see an image you love from a photographer you admire, not only remember to ask "how did you rate this film", but also "how did you meter for this image". Because, it takes both rating and metering to create the beautiful film imagery you all love so much!