Light Coverage - spill-diameter

As I use flashlights I tend to prefer certain ones over others - and not just for the size and form factor - but the beam coverage.

I tend to like lights that will illuminate an average room well as opposed to a narrower beam - where I've described it as almost like looking down a tunnel.

For example I like the Ultra-G - as it seems to cover well -
I've used the example of lighting a stairwell - standing at the top step and with the Ultra-G beam centered on the bottom step (10 steps) the overall circle of light will light up both sidewalls (that are 41" apart) from just over an arm's length away - as well as the top step - this is close to lighting up the entire stairwell.

Whereas the ArcAAA's beam was noticably narrower - so in comparison was like looking down a tunnel....

Descriptions are nice and most people will get the idea - but is there a way of quantifying this coverage?

Well, I tried it with another description of the overall circle of light filling an 8ft tall wall from a certain distance - eg: the Ultra-G from about 5ft and the ArcAAA required 6.5ft.

This was OK - but I went further and worked out the angle and the equivalent coverage of a lens on a 35mm camera.

eg: in this thread (LED Flashlight)
I found the Ultra-G and Dorcy 1AAA covered about 77deg (the coverage slightly wider than a 28mm wide angle lens on a 35mm camera) and the ArcAAA covered about 63deg (almost exactly a 35mm semi-wide lens)

So I did a little bit more measurments - placing the flashlight with the front bezel exactly 12" away from a wall - in a darkened room - I then measured the diameter of the total light circle, making sure the measurment was through the center of the beam/hot-spot to allow for any flashlights that were not aimed exactly perpendicular to the wall.

I consider the spill circle usable if I can easily read the tape measure I used.

I used a few incandescent lights that I liked for their coverage and some well known LEDs -

All light with front bezel 12" away from wall

Light/ Diameter/ Angle/ Lens equiv on 35mm camera

Ray-O-Vac Lantern/ 43"/ 122deg/ 12mm (extremeWide - almost fisheye)

Streamlight Scorpion/ 36"/ 113deg/ 14mm (extremeWide)

SureFire 9P/ 26"/ 95deg/ 20mm (ultraWide)

Ultra-G/ 22"/ 85deg/ 24mm (very wide)

Dorcy 1AAA/ 21"/ 82deg/ 25mm (very wide)

ArcAAA/ 15"/ 64deg/ 35mm (semi-wide to normal)

As you see, if you read my previous measurements/calculations - I underestimated the coverage of the Ultra-G and the Dorcy 1AAA by quite a bit - there was probably some error in measuring the distance to cover the 8ft tall wall. But the estimate for the ArcAAA was pretty much exact.

The three incandescent lights happen to be my favorites and one can see that they have very, very wide coverage so that a normal room would be very well (and brightly) lit.

The Ray-O-Vac Lantern was called their "Floating" Lantern bought about 1-2 years ago - has a Krypton bulb and orange peel reflector - very even and wide-wide coverage.

The SureFire 9P is their earlier 3x CR123 cell Xenon light. I have always prefered the Streamlight Scorpion despite it being not quite as bright, because I could adjust the hotspot to a much wider but smooth spot and the overall coverage is noticably wider than the SureFire 9P.

Comments please?

nice job--i like wide spill as well.

Bob

I second the motion- very nice job.
Long throws have their place, but nothing beats side spill in a light you are going to work (or walk) with!

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escriptions are nice and most people will get the idea - but is there a way of quantifying this coverage?

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I find that the easiest way to describe the beam coverage/hotspot characteristics is via a beamshot on a graduated target. Hence why one is included in every review at a standard distance of 1 meter (~39 inches).

like so:

E2:



Minimag:



Add to this the lux and Qups readings and you get a pretty good idea of the throw and amount of light produced overall for comparison reasons.

Calculating beam angles is great, but beamshots on a graduated target at a standard distance let you quickly "see" the difference between the beams and their width.

Good work! Your illustration with the Ultra, is why I find it very useful. Plus it is bright enough to do the job. In a similar test, I target the floor beyond the bottom step and hold the light civilian style, and it lights up the entire stairwell.

Still every beam type has its uses. The PT Impact, while not for walking, is useful for spotting at a greater distance than the Ultra.

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Quickbeam said:
is via a beamshot on a graduated target. Hence why one is included in every review at a standard distance of 1 meter (~39 inches).


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Are those circles one inch apart by any chance?

The center circle has a radius of 1 inch, and each circle beyond adds an inch to the radius. The grid dots are placed at 1 inch increments.

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Quickbeam said:
The center circle has a radius of 1 inch, and each circle beyond adds an inch to the radius. The grid dots are placed at 1 inch increments.

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Yes, graduated beamshots is another way of doing it - if we can agree on a standard distance from the target.

This is not meant to be any criticism of your excellent work that I admire greatly -

BUT - the two examples you showed seem to only show the central hot-spots, whereas the angles I was calculating/measuring were the overall coverage - spill circles if you like - although dimmer than the central hot-spot are still very usable and useful when illuminating enclosed spaces like a normal room.

You'll also note the distance I ended up having the flashlights was a mere 12" from the wall - I know that's closer than real-life practical (especially for the Xenon lights! /ubbthreads/images/graemlins/ooo.gif) but the overall usable circle of light were so wide on some, being 39" from the wall would have meant the measurement (eg: for the incandescents) would be in the range of 85"-141" - this is just a little bit beyond my "convenient" arm span......... /ubbthreads/images/graemlins/help.gif

Of course the disadvantage of using shorter distances is that the measurements become a bit more critical - small errors are larger percentage-wise - and therefore the margin of error becomes larger - but for most practical purposes I think my measurements are going to be "good enough".

Although the angle may seem more complex to measure/calculate - having the angle means one can predict/calculate the overall coverage/spill diameter from any distance.

For example the Ultra-G at 85deg from 39" would have a overall light circle of about 71" diameter - (that's over 35 circles on a graduated beamshot test target?) and the Ray-O-Vac Floating lantern at 122deg would have a light circle of 141" diameter - that's over 70 graduated circles on the test target - a huge sheet of paper.......

While the ArcAAA has a deeper reflector, causing the sidespill to be small in diameter, it also makes it brighter. I find I can make out objects better with the Arc's side spill. Also I don't find a noticeable differnce in side spill width between that and the Ultra-G. There is some, but it's nothing for me to worry about. You might have to pan a few inches in your hand, but nothing like a mag beam where you have to sweep everywhere... It lit up enough of a 8x5 foot or smaller bathroom at work just great!

Ok, my mistake. Helps if I take the time to actually read the entire post, eh? You're looking to measure the ENTIRE beam. Yes, that has to be done at extrememly close distances.

Either that or I need to paint an entire wall in my spare room with 1" spaced dots... I think my wife would kill me! /ubbthreads/images/graemlins/tongue.gif

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IsaacHayes said:
Also I don't find a noticeable differnce in side spill width between that and the Ultra-G. There is some, but it's nothing for me to worry about.

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I suppose what is "adequate/useful" is still subjective -

but for me the difference between 85deg and 64deg coverage is huge - that's the difference between a 24mm extraWide lens verses a 35mm semi-wide to almost normal focal length lens on a 35mm camera -

Just to describe this, it's like being able to stand in the corner of a room pointing the light at the opposite corner and lighting up almost from corner to corner with the Ultra-G whereas a stationary ArcAAA would do only about 2/3 that.

I just went into a windowless darkened room to compare my ArcAAA with Ultra-G - and in a normal sized room with light colored walls there was little to no difference between my ability to see with the side-spills - neither was noticably or practically better/brighter.

Except the Ultra-G covered a lot more area - and so for me was much more useful, and a difference I definitely notice - perhaps it is a bit of an exaggeration - but after using the Ultra-G, looking by the ArcAAA was like looking down a tunnel.

But as always YMMV - however I think the angles are a way of being able to quantify this "coverage".

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Quickbeam said:
Ok, my mistake. Helps if I take the time to actually read the entire post, eh? You're looking to measure the ENTIRE beam. Yes, that has to be done at extrememly close distances.
Either that or I need to paint an entire wall in my spare room with 1" spaced dots... I think my wife would kill me! /ubbthreads/images/graemlins/tongue.gif

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Tell her it's "Arc-Deco"......

I agree, sidespill is always a really important characteristic when i'm looking for a torch. But i don't like fixed lights much, i prefer to have the flexibility of a good focusable flashlight. You never know when you'll need a blinding tight focused beam for throw, but for most situations you could have the beam focused out to suit your particular needs.

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DaMeatMan said:
I agree, sidespill is always a really important characteristic when i'm looking for a torch.
<snip>
i prefer to have the flexibility of a good focusable flashlight. You never know when you'll need a blinding tight focused beam for throw, but for most situations you could have the beam focused out to suit your particular needs.

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Yep - agreed - I prefer the Streamlight Scorpion over the brighter SureFire 9P for exactly the reason of being able to adjust focus of the light - most of the time though I set it so that I have the largest central hot-spot without any noticable hole in the middle. But overall this Xenon 2x CR123 cell light is so bright that the side-spill total circle is so even and bright that it really does light up a room well. It is brighter and comparable in coverage to the much larger Ray-O-Vac Floating Lantern - very impressive for such a small flashlight.

I look forward to the day when LEDs are going to be comparably bright - and still have practically long runtimes.
OK, wishful thinking....
for now. /ubbthreads/images/graemlins/cool.gif

Hello Charlie,

"Arc-Deco" is too much...

Tom

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SilverFox said:
"Arc-Deco" is too much...

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Yes, I agree, I was LoL....

Of course one could also claim it was
"Ultra-modern" too.... /ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/tongue.gif

I tried this with my CNC-123 w/ BB400|Q2 and Dorcy AAA - i was confounded. How do you define the beam? I couldn't figure out how this is useful, so i gave up.

http://members.arstechnica.com/subscriptors/x/mark_laarson/cnc-123-04.jpg

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Mark_Larson said:
I tried this with my CNC-123 w/ BB400|Q2 and Dorcy AAA - i was confounded. How do you define the beam? I couldn't figure out how this is useful, so i gave up.

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I wasn't doing any measurements via photos - but using the actual live lights.

I don't know much about the other flashlight - but if you stand about 3ft from a light colored wall (in a darkened room) and shine the Dorcy 1AAA at it, don't you actually get a circle of light (formed by the side-spill) centered with the hot-spot?

Isn't that circle of light quite well defined, and quite practical and usable?

That's the circle of light that I measured the diameter of - which in the case of my 2 samples would be about 65" diameter, when the lights were about 3ft away from the wall.......

Does your Dorcy 1AAA behave differently?

Vincent, as you can see, the Dorcy does have a well-defined side-spill circle, but the CNC-123 does not. Maybe that's why i found it difficult to measure it.

Another thing was that the CNC-123 makes a really wide circle - more difficult to measure. I shall try again tomorrow.

Maybe my ArcAAA is brighter than most? It is of the newest version with the writting down the barrell. It is just as bright if not brighter than my DorcyAAA which is brighter than the Ultra-G.
While it's true the ultra-g's spill is wide enough that you don't have to pan at all, I don't mind panning a little bit with my Arc. It's still 99% better than what I'm used to with incandecents.