OP wants to tell a stick from a snake and there’s only one comment directly mentioning color rendering.
A light’s color rendering index can have a significant impact on how well you perceive colors, and is particularly important when you’re trying to spot a camouflaged animal. Here’s a quick comparison in which the first light has average color rendering for an LED flashlight and the second has CRI in the 90s:
To make exactly 750lm for 4h from a 20Wh cell requires the efficiency to be 150 lm/W. That is possible for flashlights to achieve, but at the upper end of the efficiency range for that much output. It likely requires a large, low-CRI LED, which I would not recommend for OP’s application.
Three comments mentioned CRI prior to your post.
CCT is another important factor besides CRI. Good luck differentiating shades of brown and black, etc., with a low CCT high CRI light source.
This would require:
-extracting a full 20Wh from the cell at the required current draw.
-the heat capacity of the light must allow a continuous operation at 750lm output.
-the optical efficiency needs to be taken into account, which can add losses of ~15% or whatever.
-the efficiency of the driver is another non-negligible factor.
I really doubt he’s even seen 450lm for 4 hrs. From my testing with a light tube, very few lights can sustain their outputs for long periods of time. I referenced the EC4S because I remember it held output for a long period of time. Handles heat very well. Another light that comes to mind is the Supbeam (Acebeam ) K40 on high, but that’s a whole other class of light and history. Lots of these lights have a ramp down from turbo, that unless you’re really paying attention, will go mostly unnoticed. A couple of my older SolarForce lights will hold 600-700 for quite a while, but not no 4 hrs
Thanks for the comments and suggestions, everyone. I ordered a Convoy L21A with SFT40 yesterday, 6500K.
I would recommend that you take either three identical flashlights or headlights with 3,4,and 5k High Cri LEDs out for a hike in FAIRLY DENSE woods. Rotate through them every five minutes. Cold white and a “neutral” 5000k causes way too much glare and shine off of trees and live leaves and other objects. It’s very distracting and causes difficulty in focusing on the ground and trail and rocks and roots and frogs and things that matter. 4K isn’t terrible but 3K is so much better. If you just take one out at a time on a hike you don’t notice how big the difference is.
And then add in a tiny little bit of rain or mist or fog or snow or smoke and the choice is clear.
That’s good advice. It is commonly agreed that lower CCT cuts through fog better, and also attracts less insects.
I use flashlights in indoor working environments mostly and also outside, but not in a rainforest. I find 5000k to be ideal for differentiating wires and paint colors and such, and for shop lighting in general.
150lm/w is doable, but only at low current, do not expect anything close from a led running near its max.
That’s going to have an extremely tight hotspot and very poor color rendering. I think it’s so far from what you were asking for that you should probably email and ask if you can cancel your order.
No need to exaggerate, it will be just fine, he will be able to tell a snake from a stick just as good with 6500k as with 3000k. maybe even better. I’ve tried dozens if not hundred different lights during decades of camping trips. I found nothing that I can not see using cool white but could see with warm white. Actually cool white gives you a better contrast and depth at least in my experience. 80cri vs 95 will not be that different in real world. At least not enough to miss anything. This is not a body shop’s paint booth, you are not matching paint, or doing fade. for outdoor activities 6500k is just fine. BTW very popular type of lights in paint booths, Verilux 6250k natural spectrum lights.
Perhaps @Kurt wants to spot snakes chillin’ in the upper branches😃.
Then he should ask Simon (if he ordered from Convoylights) to install sft40 3000k or 4000k and ask for an OP reflector.
O, and please wear high boots, gaiter and watch where you take your steps; since our equatorial slithering beauties also love damp, food-rich forest ground
You have actually a lot better chance to see that snake, on the floor, or on a tree with a flood light, not a spot. I honestly do not find spot light much useful in finding things. For a 'closer "inspection once you located it maybe, but to actually locate it, not so much. That is the reason why ships lookouts do not use binoculars, naked eye is better at spotting something, only after you spotted it, you look thru binoculars to see what it actually is.
Convoy L21A with SFT40 is going to have a super tight spot with limited spill, is it not?
A light with a smaller head, an OP reflector or medium TIR lens, and a larger LED such as XHP-70.3 HI 9050 or GT FC40 for example, would make for a larger spot and more useful spill.
Reading again our coleagues comments, I realize that maybe I was too concerned about the “search light” term, and this is somewhat we usually associate to thrower lights, but I’m afraid this is not necessary your case.
For close to medium encounters, there are more suitable models I would like to suggest you:
-Convoy M3-C XHP 70.2 R70 4000k: heavier tham average, but sustains 1500 lumens for 2:30 hours, and reaches 350m on turbo.
-Convoy M21H xhp 70.3 R70 4000k tir 8°: sustains 1000 lumens on turbo for almost 2h, throws about 300m.
-Convoy M21E XHP70.3 R70 5000k: 1000lm for 2h and 450+ of throw
-Sofirn C8L: almost 2h at 1200lm, throws 500+
You may want to carry another light for throwing, like a Convoy M21A SFT40, and you are good to go.
You can also choose the high cri versions (except the C8L), but at the cost of lower brightness and runtime.
I’m pretty skeptical of these meter/feet numbers when it comes to throw, what exactly do they mean, the spot at that distance will be visible, or will it be bright enough to read a newspaper with binoculars? CD rating would give you much better idea of beam intensity,
FL1 throw distance is how far away a light source can illuminate a target at 0.25 lux in clear air. 0.25 lux is about the illuminance of the full moon. This is usually enough to detect large objects; using a light with 500m FL1 throw, most people can easily spot a house, car, or boat at 500m.
It is not enough to see clearly at a long distance. 0.5 lux is arguably a better number, and the math works out so that’s exactly half the distance. With 500m FL1 throw, most people can easily distinguish a dog from a deer or a bear at 250m.
For something to look well-lit such that fine details can be distinguished, 1 lux might be a better number, and that’s a quarter the FL1 throw. I expect most people could read a newspaper illuminated by a light with 500m FL1 throw at 125m using a powerful telescope.
Three comments mentioned CRI prior to your post.
I missed one, but I still only count two, plus your recommendation of emitters that have high CRI without saying that. Flashlight nerds are familiar with the FC40 and know what R9050 means, but OP created their BLF account three days ago and might not.
extracting a full 20Wh from the cell at the required current draw
120lm/W / 750lm = 5W
150lm/W / 750lm = 5W with a near-dead battery at 3V is 1.67A. It is realistic for high-capacity 21700 cells rated at 5800-6000 mAh to put out 20000mWh / 3.6V = 5555 mAh under loads of 1.67A or less.
the heat capacity of the light must allow a continuous operation at 750lm output.
That’s realistic for a 21700 flashlight with a flared head and high efficiency (and the whole concept we’re entertaining here depends on high efficiency). The Acebeam E75 sustains higher levels for the entire life of the battery, for example.
[efficiency of the whole system]
A high-binned XHP70 series would need the rest of the system to be around 75-80% efficient. 85% optical efficiency and 90% circuit efficiency gives us 76.5%.
These aren’t crazy numbers, but they’re at the upper end of what we can expect from current flashlight and battery technology.
750 / 120 = 6.25
Taking 90 and multiplying it by .85 to get 76.5% is not an accurate way to calculate the losses or power requirements of the system.
Consider that you cannot calculate for 750 lumens LED output, the optical losses have to be accounted for up front, so actually the necessary LED output is 750 / .85 = 882 Lumens.
882 / 125 lm/W = 7.06W.
Applying 90% electrical efficiency to this, 7.06 / .9 = 7.84W.
From a 22Wh cell, you’d get maybe 2.8 hours runtime.
If an LED array were used and could achieve 150 lm/W:
882 / 150 = 5.88W
5.88 / .9 = 6.53W
22 / 6.53 = 3.7 hours.
If an LED array were used and could achieve 180 lm/W:
882 / 180 = 4.9W
4.9 / .9 = 5.44W
22 / 5.44 = 4.04 hours.
So if those numbers are closer to reality, you’d need LED efficiency of 180 lm/W or better, or an improvement in one of the other metrics such as optical efficiency.
Thanks for your input. These are all very new to me. I had to google to find out what CCT, CRI etc mean.
