Contrast / Lighting Ratios

[Craig_Murfin]

Hi All,

Learning more about contrast ratios and have a question regarding keeping them consistant throughout a project.

Am I correct in thinking that when shooting all the different scenes required for a Commercial or Film I would keep my contrast ratio consistant?

For example:

My character is in a bedroom at night, bedside lights are on and moonlight is in the windows....I set my Key to Fill ratio to be: 3:1

Would I then in the next scene (e.g..in the kitchen with morning sun) set the contrast ratio again to 3:1 and carry on setting my ratio to 3:1 throughtout every scene in the commercial/film?

Or because its a seperate scene I can set it to what ever I like?
What is standard practice?

Thanks!

[Gabriel Devereux]

3 hours ago, Craig_Murfin said:

Am I correct in thinking that when shooting all the different scenes required for a Commercial or Film I would keep my contrast ratio consistant?

Considering a lot of DP's don't even use contrast ratios, no.

How you wish a face/scene to be lit in terms of key/fill, mood, chiaroscuro in general is personal taste. 

Generally, continuity dictates you don't dramatically change the key/fill, lighting in general of a scene without just cause. 

However, like all aspects of lighting, key/fill ratio's are just a guideline to help you achieve your vision. The only exception I can think of is when second unit is trying to match first. In some cases the cinematographer has to attempt to match these ratios in which its a more exact science. 

[David Mullen ASC]

You only really try to match ratios on a face when shooting coverage, to match the master. And that’s just the particular face, different faces in the shot could have different lighting ratios depending on what practical sources they are standing next to. But those various contrast ratios should come close to matching in their tighter coverage.

The only time I’ve had to pay more attention to lighting ratios is when lighting a dark moonlit scene on film where I’ve decided, for example the key is 1.5-stops under but if I want shadow detail, the shadows have to be 3.5-stops under, which means that they are only 2-stops darker than the key.