Some of these terms are confusing, especially when one flashlight manufacturer’s marketing materials focus more on one of them, while another manufacturer talks about the other. How do you compare?
We’ll give a simple answer first, and then unpack it a bit more for those who are interested.
The difference between lumens and candela is this: lumens are the measure of overall light emitted from a bulb or LED in all directions, which gives a sense of the size area the light can illuminate in all directions. Candela, or candlepower, is a measure of how much light is emitted in a specific direction.
Candela (or candlepower) gets its name from back when people primarily used candles as lights. It’s a measure of roughly how many candles the light’s output is equivalent to. (Similar to how car engines are measured in horsepower from back when horses were the primary vehicles.)
When we’re talking about flashlights, many people consider candela to be more useful. Since this measurement is taking a linear direction into account, it says more about the flashlight’s ability to project a useful beam over a distance.
To put it a different way, it’s possible for a flashlight with a lot of lumens to project a not-so-useful beam in practical usage, and if you’d purchased it just because of that number you might be disappointed.
An Example of Lumens vs Candela Considerations
For instance, a flashlight with 300 lumens and a great reflector might product a nice even beam with a good throw distance and still have decent spill light (the light to the sides of the main beam). One might find that incredibly useful for general purposes.
On the other hand, a competing flashlight might have 1000 lumens but only produce useful light over a fairly short distance. It might have plenty of spill and illuminate the whole area, from a width standpoint, but not shine far enough to be helpful. Its beam may also be uneven or have artifacts in it from a poor reflector.
In this example, one might find the 300 lumen flashlight more useful than one with over 3x the lumens.
Most flashlight enthusiasts agree that overall lumens matter less than how they are used.
The Light’s Purpose
ShineRetrofits.com shares a useful analogy on this topic. The gist of it is to consider the purpose of the light, such as a lightbulb in your home versus a small pen light. The lighbulb will have high lumens and low candela because its purpose is to create a lot of light and throw it in all directions to illuminate a whole room evenly. The pen light will have lower lumens and higher candela because its job is to illuminate a smaller overall area, but concentrate that light into right in front of the user.
Sometimes you might want a flashlight that illuminates a wide area at the expense of distance, and other times distance will be more important than width of coverage.
In my comparison review of the Sofirn IF22A and Lumintop D2 as an example, I found the D2 to be more useful overall. Even though the Sofirn had a superior throw distance and max lumen rating, its beam was so focused on throw distance that’s all it was good for. It did a poor job of lighting up any area around me, and I’m not often enough in a scenario where I need to see a mile away and nothing else.
The D2, comparatively, struck a better balance of still having a solid throw distance but also illuminating a useful area in front of me. In my opinion, it makes for the better pocket light overall of the two.
Converting Lumens and Candela
Roughly speaking, 1 candela is equal to 12.57 lumens. That varies of course by the efficiency of the flashlight and its reflector. In a pinch, if a manufacturer only shares one figure and you’re curious about the other, you can use this conversion to get an idea.
Using This Info To Make Buying Decisions
When it comes to buying a flashlight and comparing various models, it’s more useful to compare the candela ratings against the various battery life ratings.
In other words, how efficiently does this light convert battery energy into a useful light beam?
It might sound impressive for a light to boast 3000 lumens, but if it can only do that for 15 minutes and it doesn’t have a good selection of lower power modes, that’s going to be a special use case light that isn’t useful for much else.
This is also why I generally ignore the “Turbo Mode” some flashlights put all over their packaging. Usually this is an inflated number that the light can only run at for 5 minutes or less, and then it drops back down to a much lower number.
To me, a lumen number that’s only possible when the battery is fully charged, and only possible for a couple minutes, isn’t something I can count on in real usage.
I am far better off, then, to only pay attention to the light’s “High Mode” since that’s a sustainable level of light that matters — and is the level the Turbo Mode will drop down to after a couple minutes.