In 2015 I publicized the Convoy S2 here on NR and it took our world by storm. Its powerful spot LED made rocks glow like we had never seen before. That blog post quickly became the most popular post here on NR. 6 months later we designed the Convoy C8 as a FB group effort, a huge leap in brightness.
Since that time there have been many copycats and clones, each with advantages and disadvantages.
Folks new to the hobby usually start out with some variation of one of these flashlights, often looking for fluorescent sodalite around the Great Lakes areas. The bright spot makes it easy to find those glowing cobbles.
But once folks collected a bunch of marvelous glowing rocks they needed a way to display them at home. This typically requires a floodlight. By its very nature a flood light is much less intense that a spotlight. The beam is spread over a large area, illuminating it all equally instead of focusing the light on an intense spot. Beam angle or pattern is a measurement of the angles that are formed between a cone of light’s brightest point (the center) and the points on both sides of the center where the light’s intensity is 50 percent as bright.
In the picture, we can clearly see that a larger beam angle means a wider spread of light across an area, and, likewise, a small beam angle means a narrower spread of light.
What does this mean? When buying flood display lights you're going to need lots of power to cover a large area. Often we just rely on near total darkness to make up for the flood beam's lack of power. Or, multiple floodlights can be installed in a cabinet, each lighting up a section. Note: this discussion is targeted towards LED type lighting. Tube lights (TL) are by design, floodlights and cover a wide area but at much less power.
A good example is the following measurements showing the power of a SW fluorescent tube light (FTL) vs a SW spot flashlight. It is very important to understand that a typical UV flashlight is a spot device. The intensity is determined by the focus of the spot. A FTL light is a flood light and will evenly light up a broad area, but at much less power than a flashlight. The image on the left shows an FTL light illuminating two meters equally at the sides - 115uW/cm2. If a third meter was placed in the center it would read approximately the same - an even flood light. The image on the right shows the same setup with a flashlight; the meters out of the spot show only 20uW/cm2. If a third meter was placed in the center of the spot from the FLT it would read a whopping 1418uW/cm2 - an intense spot light.
It should be noted that flood LED lights exist which don't have reflectors. They will operate very similarly to tube lights.
When I get home I'll add some graphics explaining this (on vacay right now)....