Using Fresnel/Reflectors to increase light output, what happens when diffused?

[analogs]

When you use a Fresnel or Bowens Reflector to increase light output from a COB light then you diffuse it in a softbox, is it the-same light output as though the fresnel/reflector was not there to begin with when diffused?

For example:
100 watt COB light > Fresnel/Reflector > Softbox

Is that equal light output to:

100 watt COB light > Softbox

Thank you.

 

[puredrifting]

To answer your question, yes, a fresnel lens, overall, is going to reduce light output over a bare bulb/COB element. But the output from a fresnel lens can be higher because
of it'a ability to focus the beam, if measured in a specifc range at a specific distance.

To answer your question practically, there is zero reason to use a fresnel lens inside a softbox. You want maximum spread to fill up the front diffusion element of the softbox, not
a tightly focused beam only illuminating a portion of the softbox. A larger apparent source will always result in softer, more flattering light that wraps around a subject more.

 

[paulears]

This is why people have struggled to compare specs for lighting for years since non-filament lighting started. If light from a source is constrained by something it becomes directional but the light you dont want gets converted to heat energy, or you reflect it back. By doing so your point source gets bigger and the light is softer. True Fresnel lenses, with their stepped lenses bend the Rays and soften them in an attractive way. Diffuser offers two proprties, bending and diffusing the Rays into multiple paths, but they also become the light source, rather than the light source itself. The COB sources are clusters so they're semi-soft to start with. They really don't work well with traditional real, glass Fresnel lenses, so we use Micro-groove Fresnel lenses, originally used I'm overhead projector screens. These soften, but not remotely like real Fresnels.

When light rays diverge the intensity drops, and the reverse happens too. The advice that they're not needed in a sftbox is dead right! Worse still is the fact that micro lense Fresnels are very very lossy because dust settles in the grooves and dims the light, making it self illuminate too. Tv people consider true Fresnels to be hard light, then we have soft light as the alternstive. Theatre people use Plano convex lenses as hard light, and consider Fresnels as soft light by comparison.