Thanks for taking the time to do this. It’s good to have this sort of information documented.
Long term, it might be nice to have this kind of information indexed somewhere for easier access than sorting through forum threads.
Also, has anyone ever done a controlled comparison of DC-Fix vs. a matte finish tape like Scotch “Magic?” I’m curious if the DC-Fix diffuses a different amount, is more durable, sticks better, etc.
I haven’t done the math or the measurements so this is just a guess, but it might just be a function of lens size. Bigger lens = more diffusion film = more diffusion.
Just an educated guess. If you already have a somewhat diffused light (eg small heavy OP reflector or frosted optics), naturally adding more diffusion doesn’t have the same impact as diffusing a very narrow beam (large SMO reflector).
Okay, here’s a thought. It would be nice if someone would test this hypothesis. Compare a small, but throwy light (such as Convoy C8), to a larger, floodier light (such as BLF Q8), both with diffusion film. I’d love to see measured results.
Doesn’t sound right. It seems to me that
Bigger lens = less light hitting any spot = just like lower mode = no effect on diffusion.
Though when pattern size is large in relation to lens size that would be different.
For example, put DC-Fix on a mule. It has virtually no effect. Then put it on a thrower, and it has a much bigger effect. The more collimated the beam, the more it can be messed up by diffusion film. But making a mess out of something which is already a mess… isn’t very noticeable.
With measurements of a bunch of lights, it would be possible to generate a curve and figure out the math. But for now, I really don’t know. The effect is probably something like sqrt(candelas) or sqrt(cd/lm). Except, instead of a square root, it’s probably a different power. Like math.pow(cd, 0.95) or math.pow(cd/lm, 0.75) both get fairly close to the numbers in the OP.
Not really, that question is about loss of collimation (amount of collimated light turned into scattered light), not about light loss.
Actually, my feeling is that the light loss by a diffuser of a floody and throwy beam should be the same.
I also would like to see the numbers for throwers and flooders but, as ToyKeeper said, the visual effect on a flooder is negligible.
Diffusers are very nice but the drop in throw has 2 effects. First you want to increase output to increase throw again. It’s totally subjective but it’s what you want to do, so one should have more lumens available… Maybe one can get used to it after a few minutes but I didn’t try it.
Second, lots of flood are inconvenient to illuminate farther away so I don’t keep it permanently on the flashlight. I carry several pieces for different flashlights in the wallet; sticking the right one on the flashlight takes less than 1 minute. Removal is also easy and it doesn’t leave dirt on the glass. Dc-fix can be reapplied several times. I glue them back in the plastic cover that comes with it in the wallet to not lose the adhesive.