Light Density

Here is an idea that occured to me last night after reading Peter G's posting about Lithiuim squeeze lights. I propose to quantify Light Density using the following equasion which is based on measurable values:

LD = (B * T)/V

Where:

1. "B" is a standardized measure of brightness or light output (measured at one minute after turn-on with fresh batteries).

2. "T" is the time it takes for the flashlight to reach 80% (or some other value) of the value of "B".

3. "V" is the volume of the flashlight in cc's. The volume can be measured by submerging the flashlight in water and measuring the amount of water displaced by the flashlight (1ml = 1cc).

By dividing the Brightness*Time value by the Volume of the flashlight, large flashlights are penalized for their size.

Comments?

KT has given CPF a nice term.
Throw is how far an incan will go.
Push is how far a LED will go.

Reason #12 why he should not leave CPF.

Sounds useful.

So to satisfy Darell, how about

LD = (B * T)/(V*M) where M = mass (weight)

We are moving away from light density though and are approaching some notion of utility.

If that's the case, perhaps we should reduce the utility value by adding an additional $/mAh of the battery:

Utility = (B*T)/(V*M*$/mAh)

Putting weight and volume aside, another aproach to the utility provided would be to look at a simple equation of:

Utility = B/(Total cost of operation for 100 hours use)

Unfortunately, none of these equations consider the all important YES factor, aka COOL.

On further thought,lumens/watt might be a better replacement for B. If you were to graph lumens/watt against time and calculate the area under the graph and then divide that number by the physical density (weight/volume) of the flashlight, you'd have an interesting measure of light density.

Calculating, or even considering, this number might be a good indication of one's own density

I've considered cost per 1000 candela hours or cost per 100 lumen hours as other factors to weigh into this.

I like it, except there is no weight penalty, as I think there should be.

It's an interesting idea, as long as people realize that it is just one objective measurement and not much can be read into it. For most people, more subjective factors end up being quite important in evaluating a flashlight. "The head is too big" or "the beam hotspot is too diffuse" or "I like the way it feels in my hand" are common arguments for and against various lights.

I would definitely like to see more object measurements to supplement the personal evaluations, though. Another thing that would be nice is a consistent, objective rating system for beam characteristics (shape, beam diffusion, color, etc.).

- Russ

What about a two-axis measurement? This could still be presented visually and it would allow for more flexibility in the choice of factors. You could still present the quotient as a summary result.

For example, the Y axis could measure some composite of the "good stuff" like brightness and battery life, while the X axis could measure some composite of the "bad stuff" like weight and cost. By plotting a bunch of lights on a graph, one could see with a glance how much sacrifice would be required to get the brightness and battery life one desired.

The quotient would give a single ratio between these two which would basically fill the role of your originally proposed index, but by deliberately choosing the components with the intention of graphing the two parts, you can give a nice way to interpret the number. If you actually had a well populated graph, you could easily spot a light that makes a nice compromise overall, or you could pick your minimum brightness and easily compare qualifying lights to see which one compromised the least to get there.

Does that make sense at all?

- Russ

Here's my example of an Ultra High Light Density flashlight....light output of an E2, output decay of a Newbeam and the size of a Photon!

In my original posting I was trying to keep the factors in determining light density easy to determine. Both Brock and Graig have light meters that give some measure of light output that they use in their reviews. If those measurements could be equated to a common value then we have "B"!

"T" is simply determined with a light meter and a stopwatch. I put "time" in the equasion because I felt that light output over a period of time should be a component of light density

"V" was put into the equasion to benifit the Photon sized E2! By dividing B*T by Volume, the value of LD goes down as the volume goes up. The volume of a flashlight can be determined either by displacement (dunking in water) or estimated by measurement with a ruler and a calculator.

The other factors mention so far are good but tend to be subjective or hard to measure! I was trying to come up with an objective value that could be determined by our reviewers and included with their reviews along with their subjective opinions about the flashlight!

Determining a scale of High LD to Low LD would be interesting! What value would be a high light density flashlight?

Interesting...

I like the idea of quantifying Light Density, but since battery capacities vary from cell to cell, won't they first need quantification?

d'mo,

Given that I'm not an expert in this area, it seems to me that battery contribution to light density is accounted for in the amount of light generated (B) and how long it takes for the amount of light to decay by some pre-determined amount (T).