Kind of yes but no one has given me a simple answer to the below,
Example:
If the key light was metered at f16, fill light at f18 and towards the camera it was f8. Am I suppose to make both key and fill the same value. I keep hearing the word ratio being mentioned but not being good at math it means nothing to me. Surely whatever the key and fill come out at its irrelevant as I end up using whatever value the meter says whilst pointing to the camera. This is my confusion, ratios etc....it's all new to me and the manuals expect me to understand but I don't
I will explain this in 3 parts
1. from a purely technical "Camera operator" POV, you are interested in how much light is "possibly" heading towards the camera. i..e. the illumination from the camera's point of view). How much light actually ends up headding towards the camera, depends on the subject. You are metering illumination, not reflection. Since (if you point the meter towards a light, or the camera), you are ignoring how reflective the subject is, in theory, if you take this meter reading, a dark object will look dark, a light object will look light, and a medium tone object will look medium toned. This method takes no account of the subject shape or colour or reflectivity, it only gives you the "averaged" amount of lighting. This is a very useful measurement, as from shot to shot, things will look approximately OK, and you can also reproduce the overall level of lighting from shoot to shoot and shot to shot
2. The ratio of lighting is literally as simple as this example: light a is twice as bright a light B, so the ratio is 2:1 (bright is a crap word to use here but it works
3. On a shoot, you use the ratio's to get the overall feel of the shot right. the ratio's are useful for remembering and setting the shot up each time.. Sometimes (say if you are outdoors in the sun), you cant change the power of one of the lights (the sun), so you alter the flash head you are using to get the right ratio. In all cases, you then need to set the overall exposure right in the camera, and you do that by pointing the meter towards the camera
In optics / photography there are a couple of principles you need to get under your belt
A. reversibility of light in a system
B ISL (Inverse squared law)
C. that the power of reflective light Vs distance
A. reversibility of light in a system... Imagine a mirror, and a laser. fire the laser in at 45 degrees, expect to get a beam of light back out at 45 degrees. move the laser to the other side (where it made the dot on the wall), and point it back at the mirror, expect the laser to fire a beam straight back where the laser was before you moved it
Bigger light sources spread light about all over the house, this means that the only true measurement you can make that is relevant is the amount of light that heads towards the camera. However, if you drew it as a diagram, you will see that the light is reflected from the subject (which inst normally flat like a mirror, and heads off in all directions)
This is why we use the towards the camera reading, because it directly correlates with the 180 degrees opisite reading of "how much light is landing on the subject" regardless of if the light source is the sun, a huge soft-box, or a tightly gridded snoot, or regardless of how many light sources there were. It is the only easy to measure relevant reading
B. ISL law
for a point source of light, the power diminishes over a distance according to the inverse squared law (google it) . In practical terms, this means that in a small studio, moving the distance of a light a little bit has a fairly big impact on how much light energy hits the subject.
C. Reflected light does not change power over distance - so in essence. Iif I meter a bride and get F8 at her face (pointing towards the camera), I can walk 10 feet, or 100 feet away, and the camera setting still needs to be F8
Equally, if I metered in front of the grooms black suit, or the white dress, the reading would still be f8 under the same lighting conditions
This is exactly why the "towards the camera reading" is so relevant as a starting point for deciding what to set your camera for
In a nutshell - set your lights up in a a"ratio" that looks nice / has the look you were looking for, and then meter towards the camera, and use that as your base setting. Experience will then tell you if you need to alter the exposure you then choose to push the look you are after one way or the other