FAQs

A. After compiling these notes and trying to get my head around all the information, I decided to put the summary at the beginning so that you can decide now if you want to torture yourself further.
Summary:
The lumens rating provides a more meaningful measurement to consider when comparing and selecting a torch. Candlepower ratings may be impressively large numbers but they are misleading and you may be bitterly disappointed if you do not also take the lumen rating into account.
Peak Beam Candlepower is a measure of brightness at a specific point.
The lumens rating tells us the total amount of light present in a beam pattern.
I have had customers who have been bitterly disappointed with the light output of million candlepower torches they have purchased from their local hardware.

A more detailed answer
A. Lux is the unit of illuminance and is measured in Lumens/ sq M .
It quantifies the capacity of the torch to project light over a distance. Lux is only measured at the very centre of the beam.

For example, a 1 watt luxeon LED with a tightly focussed beam could have a higher Lux reading than a 5 watt Xenon with a wide beam. The Xenon produces much more light but the tightly focussed LED will project light further.
Similarly, two torches, one tightly focussed and one with a wide beam, could have the same Lux rating but the wide beam would produce far more light. Another consideration is the area over which the Lux reading remains constant. Two torches may have the same lux rating but one may have a relatively uniform rating over the entire beam area whereas the other may have only a fractional rating at the beam perimeter.
The design of the lens and reflector greatly influences the Lux rating and can even vary between torches of the same model depending on manufacturing tolerances.
The Lux measurement alone should not decide what you purchase. In order for it to be an effective contribution you will need a beamshot showing the target area, its distance from the light source and the reduction in the lux reading as the periphery of the beam is approached.

Very few manufacturers provide Lux ratings. This may be because of the complexity of the measurements and the practicality of providing this information in a simple and meaningful manner.
Candlepower, or more particularly Mean Spherical Candlepower is a measurement of luminous intensity and is measured in candela which is lumens/steradian.
The candlepower rating does not tell you how much light will fall on the object you want to illuminate.
Some torch manufacturers refer to “Candlepower” ratings when they actually mean Peak Beam Candlepower ratings. This may appear less confusing than Candlepower but also leads to misconceptions regarding the ability to convert candlepower to lumens.
Peak Beam Candlepower is another thing altogether.
Peak Beam Candlepower is a measure of the brightest spot in the focussed beam and is determined by both the output of the lamp and the efficiency of the reflector. Consequently, peak beam candlepower is an imprecise measurement and each manufacturer has their own way of measuring it.
For this reason, peak beam candlepower ratings of torches from different manufacturers will not provide an accurate comparison of brightness.
Peak beam candlepower ratings can be very large (and very impressive from a marketing perspective) but can lead to disappointment and dissatisfaction if that is all you rely on to make your decision.
Peak beam candlepower is sometimes referred as centre beam candlepower.
The Lumen is the unit of luminous flux (also called luminous power), the flow of visible energy. It is the measurement of the rate of flow of light and unlike candlepower it is a measurement of light flux irrespective of direction, except for LEDs where lumens is the measurement of all the light inside the beam angle.
The lumens rating provides a more meaningful measurement to consider when comparing and selecting a torch. Candlepower is misleading if the lumen rating is not taken into account.

Q. Can I convert Candlepower into Lumens.
A. It cannot be done.

These have two different units of measurement.
Peak Beam Candlepower is focussed light and is measured in candela and Luminous flux (power), measured in lumens refers to unfocussed light.
It is absolutely impossible to convert the two as the focussing efficiency of the reflector is not taken into account.
You may see advice that candlepower (candela) can be multiplied by 12.57 to convert to lumens. This is actually referring to the ratio of Mean Spherical Candlepower to Lumens that only occurs in one specific situation of spherical photometry. It is not a conversion factor, even in that situation.
A light source that equally irradiates 1 candela of luminous intensity in all directions will produce a luminous flux of 1 lumen per steradian. A sphere has 4pi steradians so the 1 candela source will produce 12.57 lumens.
This is a calculation only, not a conversion factor. It only applies to mean spherical candlepower ratings for point sources radiating light equally in all directions. It cannot be applied to a focussed light.
Example 1 - the 20 watt lamp used in the Streamlight SL-35X is rated at 450 lumens or 35.8 mean spherical candlepower but the torch is rated at 400 lumens and 40,000 peak beam candlepower.
Example 2 - The Streamlight Litebox spot light and flood light both use the same 20 watt lamp and both are rated at 400 lumens but the spot light is 105,000 peak beam candlepower whereas the flood light is only 3,000 peak beam candlepower.
Example 3 - A LED with a luminous intensity of 9200 mcd (millicandela), drawing 20ma current and a beam angle of 15° has a luminous flux of 0.4945 lumens, whereas a LED with a luminous intensity of 1800 mcd, also drawing 20ma and having a beam angle of 50°, has a luminous flux of 1.9505 lumens.

BATTERIES

Q. Do I need to fully discharge my lead acid battery before recharging it?
A. No. Routinely running the lamp until it extinguishes will drastically shorten the life of the battery.
Lead acid batteries need to be fully charged. The higher the average charge on the battery, the longer it lasts. Deliberately draining a lead-acid battery will quickly destroy it.

Q. How long will lithium batteries last.
A. Non-rechargeable lithium batteries used in torches will have a shelf life of
5-10 years. The burn time will be similar to an equivalent alkaline but the discharge curve will be flatter providing “usable” light for a longer period than would be provided by an alkaline battery.

Q. Should I select a Rechargeable or Non-Rechargeable Torches?
A. The operating costs of non-rechargeable torches are significantly higher and they are usually not as bright. Torches incorporating recoil LED technology may be the exception. The shelf life of alkaline and lithium batteries is excellent with the latter often rated to exceed 10 years.
Rechargeable torches have an extremely low operating cost and usually can accommodate more powerful lamps. However, the initial cost is higher and their self discharge rate is greater.

Q. Can I use rechargeable batteries in a torch that specifies the use of alkaline batteries?
A. The short answer is “NO”, unless recommended by the manufacturer.
I am not aware of any that do.
Manufacturers do not support the use of batteries other than those listed in the instructions. Normally the lamps and current regulators are designed for a specific type of battery and using other batteries often results in poor performance, either low output or extremely short lamp life, depending on the battery types involved.
For example, many LED torches are designed to take advantage of the slow chemical reaction in alkaline batteries which actually regulates the current to the LED. If the alkaline was replaced with a NiMH rechargeable battery which can supply energy at a far greater rate, the LED may burn itself out or become very bright and run for a very short time. I have also read of instances where the extra heat generated actually began to melt the reflector.
I have found contrary advice (not from torch manufacturers) but the suggested circumstances are very restrictive and conditional AND their implementation will void any warranty regardless of the accuracy of the advice.

Q. Is there any way to prevent Ni Cd batteries from developing a memory?
A. Streamlight advises that the “memory effect” is almost non-existent in high-drain applications such as torches and provide these tips to help prolong the life of Ni Cd batteries:-
• The torch should be returned to the charger when it is not in use or when it begins to dim.
• It should never, ever be run until the battery is completely exhausted.
In short, operate your torch as per the manufacturer’s instructions and you will not void your warranty.
Rechargeable nickel metal hydride batteries (Ni-MH) do not suffer from this effect.

Q. If I replace my Steady Charger with a Fast Charger, will the fast charger shorten the life of my battery?
A. No. Batteries have an expected number of charge/discharge cycles (the number varies by the type of battery)

Q. Why does the brightness vary between LED torches from different manufacturers even though they use the same batteries?
A. The type of LED used may be the answer BUT, there are manufacturers who “over-drive” their LED’s. This will result in a very bright light during the first hour (remember this is when you are making your decision to purchase) but with the battery losing power rapidly, the light dims fast. A true comparison can only be made after 1-2 hours of use.

Q. How is battery burn time measured and do all manufacturers use the same method?
A. Unfortunately the method of measurement is not uniform. For example, Lightwave considers the battery burn time to be the time elapsed until the light is just sufficient to allow a newspaper to be read from 150mm.
Consequently, the battery burn times provide a relative indication of performance rather than a standard measurement for comparison.
Having said that, a standard comparison would still be of limited use as what is “usable light” would depend on the application and the user’s expectations which may simply be a personal preference.
NB. Battery burn time is a useful tool in comparing the “real” costs of different torches. Then you need to consider the cost difference in batteries to have the unit with the lower burn time, run for the same time as the type with the longer burn time.

Q. Can I use rechargeable CR123 batteries in any of the Streamlight flashlights?
A. No. Streamlight products are optimized and the components can be damaged or destroyed by the use of anything other than the recommended battery type. The use of improper or substandard lithium batteries can be especially dangerous.

Q. Can I use rechargeable batteries with LED torches?
A. Manufacturers do not support the use of batteries other than those specifically listed in the instructions. Normally the lamps and current regulators are designed for a specific type of battery, and using other batteries often results in poor performance, either low output or extremely short lamp life, depending on the battery types involved.

GENERAL

Q. How can I compare the “true” costs of LED torches and those with conventional lamps?
A. Well, we have no knowledge of your application or personal preferences, that we cannot put a price on, so we are restricted to comparing operating costs.
Battery and lamp costs make the big difference.
For example if the chosen LED torch uses 3 “D” cells and has a battery burn time of 90 hours but you want to replace the batteries at 63 hours to provide sufficient light for your application.
Your total cost for the LED torch over 90 hours will be the price of the torch plus one set of batteries.
Now compare this with a conventional torch with a krypton or xenon lamp and having a 9 hour battery burn time. If we replace the batteries after 7 hours then you will need 27 batteries to achieve the same battery burn time of 63 hours.
Your total cost for the conventional torch over 90 hours will be the price of the torch plus 27 batteries, plus replacement lamps!

Q. What colour light source should I use to preserve my night vision?
A. Firstly, we are referring to the colour of the actual light source, not light
that has passed through a coloured lens.
Secondly our night vision capability can vary depending on the amount of sunlight we have been exposed to. One study of pilots that found that a full day in the sun significantly affected night vision and ten consecutive days of sunlight exposure reduced visual acuity, visibility range and contrast discrimination by half.
Red is the best light for preserving night vision provided you only use the lowest light level needed. However, it is not always practical as, if you are reading a map, then a red light will cause the red lines to disappear so a low level green light would be best.
Whichever colour is used, it must be at the lowest level needed. Any higher, and night vision will be degraded, just as with white light. If you require more detailed information, then this is one link I would recommend - http://www.flashlightreviews.com/qa/nightvision.htm
Green is often favoured by hunters as apparently animals cannot see or are not bothered by a green light.
Some people assume green is preferable for night vision, referring to the green displays used in military night vision equipment. The display colour in these equipments has nothing to do with preserving night vision. Our eyes are most sensitive to green and as the images on such equipments are poor and “grainy”, the green allows users to see detail that would be lost on other colour displays.

”When a serviceman is in a situation requiring night vision equipment, preserving night vision is of little importance. After all he is using night vision goggles because he has insufficient night vision.”
This observations on night vision equipment was made by a 24 year veteran of the United States Marine Corp.

Q. Why are torches normally not rated in watts?
A. Light bulbs for the home are sold by their wattage because it is a practical (although inaccurate) way of comparing bulbs of the same technology. The issue would be too confusing and complex if reflector efficiency, beam angle and light frequency had to be considered.
The problem of using wattage to compare household bulbs has become apparent with the introduction of fluorescent bulbs produce far more light than an incandescent bulb of the samw wattage.

Q. Why would I want to use LED’s instead of Xenon lamps?
A. The choice of LED or Xenon largely depends on the application the light will be used for. The most obvious advantage of LEDs is their long life (50,000 to 100,000 hours) and their ruggedness. LED’s can be good for close-in lighting for extended periods of time. Xenon has always been considered better for lighting objects at a distance. However, this is being challenged by the introduction of Pelican’s Recoil LED Technology and Streamlight’s C4 Photonic Crystal technology. These technologies produce a far more intense beam so that you get the advantages of long-run times and indestructibility of an LED with an increased level of brightness that previously was only available with Xenon/Halogen lamps.

Q. How do I choose the correct light for my application?
A. We cannot make a decision for you. However, if you click on the "Choosing a Torch” link on the homepage, you will find suggestions as to what characteristics you may need to consider.

Q. How do I clean the lens on my torch?
A. Never, ever use anything abrasive. Clean with a damp cloth when the lens is cold. If any marks remain then dry the lens and use a clean, dry pencil eraser (not a pen eraser) in a circular pattern.

Industrial Torches

Popular Brands

FAQs

Industrial Torches

Categories

Popular Brands

FAQs