opal gel

[cnabers]

I have recently noticed a lot of cinematograprhers mention the use of Opal gel in thear shots(American Cinematographer mag, internet forums etc). It seems that they are primaraly used in CU's. Can you go over the techniques and effects of using this type of gel. Note: I shoot on Digital, DVX100a, XL1S etc., balanced for 3200K when doing interiors.

Thank You

 

[David Mullen ASC]

Opal is a very light diffusion gel, that's all. It's not particularly better for close-ups in terms of getting a soft light look because it's so thin, but sometimes that's all the diffusion you want, if you've established a hard key the wide shot and just want a hint of softening for the close-up.

Otherwise, a frame of opal may be used to FURTHER soften a soft light when moving into a close-up, putting a 4'x4' frame of it just off camera between the soft key light and the face in the close-up.

You need to use all sorts of strengths of diffusion gel depending on the situation. Some people would have 4'x4' frames of Opal, 250, 216, Light Grid Cloth, Full Grid Cloth made, for example (in order of strength from lightest to heaviest).

 

[cnabers]

gel frames

gel frames

What are the benifits of putting gels/diffusion on frames vs. putting them directly on the fixture?

 

[David Mullen ASC]

When you put diffusion in front of a light, the diffusion itself becomes the source of light on the subject, and its softness is determined by the size of the source relative to the distance to the subject.

Therefore if the piece of diffusion you put on the barndoors becomes something close to a 1'x1' square, that's as soft as the light can ever get (which is not very soft being so small) and using heavier and heavier diffusion won't make the light any softer, once that 1'x1' area is filled evenly with light.

So at the same distance, a 4'x4' frame of diffusion produces a much softer light than a 1'x1' diffusion. Distance relative to subject also matters; a 4'x4' frame and a 12'x12' frame would be the same softness if the 12'x12' was farther away; the difference is FALL-OFF. When you have diffusion much closer to the subject, then as the subject moves closer or farther from the light, they get visibly brighter or darker. When the light is farther away, then moving a few feet closer or farther to the light won't make much of a brightness difference.

So you would only put diffusion right on the light if you wanted to barely soften it. The advantage is that being a semi-hard light still, it would be easier to flag and direct -- for example, you could then put a snoot of blackwrap around the light to control the spill. A 4'x4' frame requires much bigger black flags to control the spill, and this takes up more space.