how many lumens are needed to read

hi people,
once more a (stupid??) question from me.

One of the uses for my new (to be decided) flashlight
will be for reading at night (obviously) in my tent.

it'll be hanging from the 'ceiling' about a meter (3.5 feet) from the floor,
and needs to give enough light for two people to read by
reasonably comfortably. the books will be at about groundlevel.

how many lumens would I approximately need for this?

thanks for your time,
Jurjan

depends on how the light is focused. a 80lumen LED would be the same brightness as a 5mm LED if a reflector is not used.

All and all I would say 2-3 lumens will be plenty,


Nick

ooops, you're right offcourse..

I'm thinking of three lights:

1) Aleph 2 (1 and 2 X C123)
2) McLux PD
3) HDS EDC 60 ult

in no particular order..

any advice is welcome.

for example: aleph 2 with standard tailcap: easy to hang from ceiling,
the other two??? I'm not so sure..

greetings,
jurjan

you can't go wrong wit hall three of them, the low on the PD will be perfect, and are the lower levels on the u60. don;t have a Aleph but i imagine a 30 ohm model would be good too.

jurjan said:

ooops, you're right offcourse..

I'm thinking of three lights:

1) Aleph 2 (1 and 2 X C123)
2) McLux PD
3) HDS EDC 60 ult

in no particular order..

any advice is welcome.

for example: aleph 2 with standard tailcap: easy to hang from ceiling,
the other two??? I'm not so sure..

greetings,
jurjan

Click to expand...

What is also an attractive option would be a LionCub. ON UI2 Level 1, it is perfect for reading, but on level 5 you can really fire up that TXOJ to the max! the light has a flat bottom to use in candle/lamp mode, and a lot more features built into the interface!

Geologist said:

What is also an attractive option would be a LionCub. ON UI2 Level 1, it is perfect for reading, but on level 5 you can really fire up that TXOJ to the max! the light has a flat bottom to use in candle/lamp mode, and a lot more features built into the interface!

Click to expand...

So does the HDS...plus the four selectable levels makes instant access almost like second nature.

Geologist,
where can i find out more about that lioncub?
I'm keeping my options open for the moment so i'd like to look into it as well.

mmh are you a geologist???
i studied it myself. nice

have a nice day
jurjand

For two independednt reviews, Cones and LED Museum have excellent write ups with photos of the various incarnations. I'd be happy to answer in questions as well as probably many members here. The light is also easy to change the star if you decide to change it later. The light has two user interfaces, multiple brigtness levels, autolockout, force mode (to always have the light come on at a certain brightness level), brightness memory, etc. There are also optional "turbo heads" (called LionHeads) to give the light throw like a much larger light, and differnet battery tubes. The lights were made in Bare AL, Brass, Black and Natural HA, and Titanium.

There are currently a lot of extra LionCubs on the market being bought and sold.

Cones link: http://www.cones-stuff.co.uk/Mr Bulk LionCub.htm

LED Museum : http://ledmuseum.candlepower.us/third/lioncub.htm

Oh and buy the way, I am a Geologist, but currently not employed as one.

Geologist,
hhrrmmm.. those lioncubs do look nice.
sound like my shortlist just got one item longer..
sigh..

it's supposed to get SHORTER.. not longer...

btw: funny, i'm not in the 'trade' as well..

have a nice day
jurjan

Hello Jurjan,

Welcome to CPF.

For reading in a tent you actually need to be concerned with Lux, rather than lumen, measurements.

Lumen's will tell you how much light the flashlight is capable of producing, while lux (or foot candles) tell you how much light is falling on the object you are trying to light up.

Depending on the size of the print in your book, around 20 lux should be a good comfortable minimum level for most reading. If your eyes are good and the print is not too small, you can get by with 10 lux, but you may suffer from some eye strain.

Tom

Tom, or should i say SilverFox,

Thanks for the welcome.

mmmhh that's what i don't get.. what do the different measurements mean?

for example, if i remember correctly:
McGizmo does all in lux measurements,
HDS does all in lumen

is there a conversion possible, or is it something different?

thanks for your time
jurjan

jurjan said:

is there a conversion possible, or is it something different?

Click to expand...

Lumen is total light output independent of how the light is focussed.
Lux and candlepower are a measurement of how far the light throws.

A laser pointer has a relatively low lumen output but is collimated to a...well laserlike beam which can hit the clouds.

A 100w halogen bulb puts out way more total light, but without a reflector you don't get high lux readings. Hope that helps a bit.

Alex/Lexus,

thanks..

have a nice day,
jurjan

I recomend the ARC AAA

Why wouldn't you use an led headlamp each? That way you can get by with less output and have zero shadows on your pages.

As already stated, it's lux not lumens that determines surface illumination. 1 lux = 1 lumen per square meter.

My HDS EDC U60 on level 17 produce 0.23 lumens. At 1 meter distance with dark adapted eyes I can easily read fine print. So the minimum illumination required for reading is below 1 lux, although for comfort you'd probably want more.

That's the benefit of a variable output light like the HDS -- you can select exactly the output you want, which could easily vary with changing conditions.

At low output levels the HDS will run over 300 hours.

OTOH there are various small LED lanterns purpose designed for long run time, and activities like tent reading.

http://www.flashlightreviews.com/reviews/riverrock_lantern.htm
http://www.flashlightreviews.com/reviews/lantern_jk164c.htm

In TOTAL darkness, any cheap 5mm LED flashlight/lantern is prefectly ok to read (close range, of course).

However, in partial darkness (dawn conditions/poorly iluminated spots), the less powerful lights seem to lose their ability to light things up.

This gets more evident especially when using LEDs instead of average incans. But i prefer LEDs anyway.

Hello Jurjan,

It is very difficult to go from lux to lumens or back. There are some rough approximations, but it is best to stay with the measurement type that provides the information you need.

Tom

Hello Joema,

I agree that 1 lux = 1 lumen provided that the lamp is radiating light in all directions and that the 1 square meter is evenly illuminated.

Unfortunately, an LED does not illuminate in all directions. This means that we have to make some adjustments.

Put an LED behind a reflector and we have changed things again. Now we have to integrate the hot spot and the spill to determine what would be an "even" illumination value.

Doug (Quickbeam) measured his HDS U60 at the minimum level and discovered that it put out 7 lux of illumination. That means that the 0.23 lumens that you refer to is being focused to illuminate an object with 7 lux.

I agree that you can get by with 10 lux or under, but it has been my experience that 20 lux is much more enjoyable. With the extended run time at these low levels, why not enjoy your book?

Tom