That was a factor in my decision of how many LED's and where to mount them. The figure below from Firehouse shows that brightness stays reasonably high (90-100%) until you exceed 25 degrees. Another 25 degrees (for a total of 50) and you are at 55% light light intensity.
One light mounted to the bottom won't be very visible if you are 1600 ft away and 400 ft high. In that scenario, your angle is only 15 degrees and the amt of light intensity is very low at 25% (or less). This strobe max brightness is 600 lumens so you would be at 150 lumens or less.
Triangle Calculator
Ideally, you need one on every side of the Anafi. I had considered a top 3D printed clip to snap over rear batter, sides, and just behind the giball from the top -- with three LEDs to cover the sides and rear. And then a fourth up front below the gimball. Using 4 arc lights and plastic mounts would weigh over 30 grams. Or you could use strobon LEDs (one cree/battery each) and get down to 20 grams.
To reduce weight and complexity, I chose to put one on the front and one on the back and angled downward slightly from the horizon. Two arcs/mounts and about 15 grams total. When the Anafi it flying away from me it's easier to keep track so I put the red flasher (has slightly lower light intensity vs white) on the rear. My biggest challenge is turning when the anafi is far away. The bright white on the front will help me find it when returning. But, unfortunately, neither of these will be visible from far away if the anafi is flying perpendicular to me. Need additional side mounted lights for that.
You could still try a bottom mount to assess if it's helpful or not. The new Arc V has 1000 Lumens of output so bottom-mounted could still deliver 250 lumens at more extreme side angles. However, the really bright strobes like the one used here are nearly 1/2" thick and there's very little clearance beneath anafit to mount it. Need leg extensions, or this mount that I've designedcould be modified to clip in the same area (or both sides) and aim straight down. You lose ground clearance as you travel from just behind the gimball to further toward the bottom side center of the anafit so it has to stay just behind but near the gimball and might obstruct a downward camera angle.
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