Q on metering for Studio Portraits
I've recently read several contradictory approaches to metering using a flash meter (or incident meter and hot lights) and employing either softboxes or diffusion panels +/- reflectors/subtractors or perhaps a fill light in place of reflector.
I've always adjusted lights to first produce a good lighting effect (whatever that may be in the eye of the photographer) and once the lighting setup is deemed pleasing, a meter reading is made by aiming the (flash) meter incident dome at the camera and setting the camera accordingly. If for some reason a lighting ratio really needs to be determined, a reading from each light alone can be made by pointing the meter dome at the camera from the subject position, taking care to shield the dome from the effect of any other light source (fill or reflector), and the ratio determined.
Others are suggesting that the lights be placed to first produce a specific lighting ratio, determined by pointing the dome at first one light source then the other (rather than at the camera), and then adjusting the ratio precisely by moving the lights or powering the lights up or down as needed. Once the ratio is precisely determined (e.g., 3:1) then the meter is again pointed at the main light source, shielding the meter dome from the fill, and the exposure recommended for the main light alone is used to take the picture. Some advise taking an average between the main and fill lights, again pointing the meter dome at the lights.
The latter two procedures make no sense to me since the effect of the two lights is cumulative. As a result, I would suspect that the reading from the main light alone would cause overexposures. And, taking an average between the two should result in even greater overexposure errors. Also, I don't understand what the point is about aiming the meter at the light source instead of the camera. Pointing the meter at the light source would produce a reading that, if followed, I would think would result in some degree of underexposure. Perhaps these two effects cancel each other out but it sure seems a strange way to do things to me and I would have no confidence in the meter doing it that way.
I've now read these conflicting techniques in several places and have asked a few photographers I know about their use of flash or incident meters and portrait setups, and the responses have varied considerably. Some say meter the main, others say base the exposure on the fill. Some are pointing the meter at the light, others at the camera. Some are setting exposure based on one light, others are taking an average, and some are using the meter reading of both sources simultaneously. Of the two studios where I've worked, meters were rarely if ever used, and if used, were employed just to get in the ballpark. The photographer then either relied on Polaroid to fine tune things or they had already tested their lights by trial-and-error and had marks on the floor where lights should be placed to produce such and such an effect or lighting ratio.
So, I'm wondering what photographers who specialize in studio portraiture do to determine proper exposure?