Hi. Previously I was using open faced lights but have now got a couple or Fresnels. Was wondering roughly what diffuser level and type a Fresnel was equivalent to (compared to open faced).
Ultimately what I think I want to go for is something like what I did get on an open faced with a 1/4 (lee 251) defuser or a Hollywood or Opel frost but understanding the level of diffusion I would get with a Fresnel would be a good start.
Or what other slight delusion was good for fresnels.
Ben Edwards - Freelance Picture Editor
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Your post title is about lighting interviews, so given that and your questions about diffusion qualities, I'd imagine you're talking about using these fresnels to light the people themselves? Or do you mean lighting the backgrounds/other items in the frame?
Fresnel lenses don't really "diffuse" light in the same way that actual diffusion does. They really just provide directionality, shape, and controllability to the raw lumens coming from the lamp itself. To directly answer your question, using a fresnel raw with no diffusion on people for an interview is not going to be a whole lot better than an open-face unit. Might be just the SLIGHTEST bit softer, maybe, but it's going to be pretty hard lighting either way.
Unless it's the only option you have, putting a fresnel through diffusion largely defeats its purpose, which is to provide you with a controllable, harder source that doesn't spill where you don't want it to. The tapered, focused beam of light is largely nullified by all but the lightest of diffusions, and it just isn't the most efficient use of the unit.
This is why you don't often see fresnels going through a softbox, it's much more efficient to just use an open-face unit with diffusion. All the fresnel is really going to do at that point is eat up light unnecessarily as all its benefits are largely negated. It's a better option to shoot an open-face light through thicker diffusion to light people for interviews, provided, of course, that softening the light on the person is the goal.
IMO fresnels are best suited to light backgrounds or set elements, where you can "paint" with light without diffusion scattering the light everywhere. On the occasion where I want to take a BIT of the edge off the light but still want to retain the overall beam shape and directionality, I'll use a very subtle, very light bit of diffusion like Hampshire Frost or something akin.