Although a lot of people think about theatre or movie spots when they hear the word Fresnel, the origin of the name Fresnel is actually in lens building. However, as we are talking about a photography modifier, I will skip that part and focus on the use in photography.
When I think of Fresnel spots I think about Hollywood, that beautiful light quality that can make a model “pop”, yet also look beautiful (often also thanks to some diffusion on the lens). The Fresnel spots have one thing that I really love: they have a tremendous contrast and deep saturated colours (due to that contrast, of course).
Over the years, I’ve tried a lot of modifiers and found some that I really like and that come close to the Fresnel. For example, the maxilight with grid, but... it’s not a Fresnel.
With most Fresnel spots, you are able to move the strobe/light source inside the housing to “focus” the beam or, in other words, make it wider or narrower. In the FS30, this is done by mounting the strobe inside the housing and using the wheel to move the strobe closer to or further away from the lens. This not only means that you are able to control very precisely the size of the spot but you can also play with your light fall-off with other modifiers. If you wanted the same diversity, you would need to use different grids and, trust me, it’s always a compromise, which often results in moving the strobe further away or closer, which again means you have a different light fall-off.
With the FS30 Fresnel, you have a 20° to 60° spot, which means you can move the strobe very precisely and create the exact look you want.