Exposure

“Expose to the right” of a histogram is a still photography concept, similar to Ansel Adam’s old adage “expose for the shadows and print for the highlights”. It has very limited use in cinematography because generally the goal is to not expose every shot as if it were unique and stand-alone, but to expose a sequence of shots for a scene so that they fall within the same range of correction (in the old days, so the shots in a scene use printer light values that are similar.) In moviemaking, you have the issue of continuity and consistency of coverage across a sequence (if not the entire movie) which is less relevant in a single still photo.

Let’s say you had a wide master shot of a room where one person is supposed to be standing in a dim area (3-stops under) whereas another person is standing under a light of moderate brightness (normal exposure) while a third person opens a curtain and is hit with sunlight that is a number of stops over.

In coverage of singles, the person who gets hit by the very hot light is naturally “exposed” to the right side of the histogram.  The person under the lamp of normal brightness might have to be overexposed by three stops (depending on tones) to get close to the right. The person in the darkness who is 3-stops under in the wide shot would have to be exposed maybe 6-stops brighter to get close to the right side of the histogram!

So first issue is how this looks on the set — who is going to “fix” these radically different exposures to look as they should for the scene? A DIT maybe, otherwise the director is going to wonder why this moody scene is all over the map in terms of exposure in the coverage. And will these corrections be applied to dailies?

Second issue is that the shots that have to be darkened a lot more to get back to the correct look will have less noise than the shots that didn’t need any adjustment.  In other words, the person who already was nearly at the clip point by being in the bright light might have the noise of ISO 800, let’s say.  But the person who was darkened by a number of stops in post to look correctly dark now has the noise of a low ISO setting.

So for consistency of noise across coverage, you should pick an ISO that works for the whole scene and then expose each set-up for the creative look you want.  If you are having noise problems with the dark areas of a particular shot, then your base ISO is too high.  Some people might choose to rate an Alexa at ISO 400, for example, instead of ISO 800, just to have a lower base noise level.

Now there is some flexibility here, you can choose to “play it safe” and when you start covering the person in very dim light, you may opt to give them a bit more exposure “just in case” — but I’m talking about a small adjustment, not many f-stops of overexposure to get the subject to the right side of the histogram.  You also may choose to use a slightly lower ISO in scenes where noise might be a factor, like when shooting green screens.  Or when shooting subjects and sets that are very dark in tonal value.

Shoot it the way you want it to appear on screen.

For example in this shot where would be the right point to read the light meter? I suppose the goal of the shot was to preserve the details in the shadows to make the actor still visible without overexposing everything else, so my guessing is that i should read it by the actor and dim the light in the background in a way that what is under the key light is not completely overexposed…is it correct (or at least not too far from the solution, ah ah!)

Thanks a lot Roger!
I’m sure that a master like you can judge by eye better than any artificial tool , but i’m just an unexperienced amateur and i feel the need to some kind of objective reading.
I’ve to say that with the camera metering, the histogram, false colors etc etc it’s not that difficult to calculate the correct exposure. What i find way harder is to find the right lighting style and photography for a given scene, that is something that comes only with experience.
Anyway, in a couple of weeks i’ll be shooting my first short movie and i’ve to trust my instinct about finding “the right” photography for it. And I feel i’m going to jump full speed in a disaster, ah ah. The new Ed Wood could be among you, be aware!

Thanks Roger! Full speed then!

By the way, I said to my wife you encouraged me and It seems this finally convinced her about helping me with my short movie (She’s not very confident abouout my ability, ah ah!). So, I owe you!

Incidentally, this means also that, in case of a complete disaster, she will consider you too responsible of that…so i’ll do my best to avoid to put you in trouble! Ah ah! Don’t worry anyway, she’s not that dangerous.

Usually.