Cinematography-Theory-And-Practice

completely independent of the frame rate. It doesn’t matter whetherthe film is moving at six frames a second or 600: the exposure willbe the same.Here’s the problem. We read the tungsten and have to compensate,we then read the strobes with a meter and we don’t have to compensate;not all light meters can do this — you need a meter that canread strobes. Clearly we can’t read them at the same time. How dowe arrive at a setting for the lens? The answer is intuitively obvious,but mathematically a bit complex: we read them separately and thenadd the two exposures. As it turns out, adding f/stops is not especiallysimple. Let’s take the simplest case first. We read the Unilux byitself (and it is very important to turn off all tungsten lights when wedo this) and find that they are an f/5.6. We have to balance the tungstento do that. As we know, at 96 fps, we have to set the tungstenlights for f/11, which will be f/5.6 at 96 fps. The temptation mightbe to average them; that would result in a very incorrect exposure:we must add them.What is f/5.6 plus f/5.6? No, it’s not f/11.2. In effect we are doublingthe amount of light: the tungsten is providing f/5.6 and theUnilux is supplying an entirely different illumination, which is alsof/5.6. Twice as much light as f/5.6 is f/8. Recall that each f/stop representsa doubling of the amount of light. Now it gets a bit stickier.Let’s say that the Unilux is f/8 and the tungsten is f/5.6. Think ofit this way: if f/8 is a base of 100%, then the tungsten light is 50%(one stop less equals 1/2 the amount of light). We then have 150%of the base light. 150% of f/8 is 1/2 stop hotter than f/8 — f/8 and ahalf. If the one of the sources is f/8 and the other is f/4, the correctexposure is f/8 and 1/4. F/4 is only 25% the amount of light of f/8:125%. Although a flash meter is the preferred method many ordinaryelectronic light meters can read high-speed strobes. The reason isthat at 60 flashes per second, it is seen as continuous by some meters.Typical ExposuresUnilux is switchable for four intensity levels. The Unilux H3000System is switchable to 16 speed ranges, which gives 1/4 stop levelcontrol. The levels are determined by the speeds at which the lightsare flashing. Remember that the flash rate is twice the camera speedbecause there is one flash for the shutter and one for the viewfinder.The lights only come up to full intensity when the camera goes tospeed. If you want to take a reading, the lights must be running atspeed. Other considerations:ingthe lens and looking at the shutter with camera running andstrobes operating. The shutter will be “frozen” and it shouldappear open.split sync mode. Inthis case there are two flashes for each rotation of the shutter:one for the exposure and one for the viewfinder. rented without operator, but be sure to check. Unilux consumes 5 amps per light. The Unilux H3000 systemrequires 220 volt single-phase and 10 amps per light.chronization.cinematography318