Recently did a quick search on use of opal gel, mainly because I'd encountered it a few issues of American Cinematographer from last year. Discovered a forum thread on precisely the issue (http://www.studentfilmmakers.com/bb/showthread.php?1444-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."
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)."
Which raised another question for me which I hadn't properly thought about -- what sort of considerations do go into deciding how hard or soft a light should be? Is it just a matter of experimentation and taste, or of trying to get the image in frame to look like the image in your head? Are there any sorts of rules or guidelines here?
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."
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)."
Which raised another question for me which I hadn't properly thought about -- what sort of considerations do go into deciding how hard or soft a light should be? Is it just a matter of experimentation and taste, or of trying to get the image in frame to look like the image in your head? Are there any sorts of rules or guidelines here?
