Can someone explain about Lumens?

[Andy in Germany]

For some time I've been developing a mildly crackpot idea about improving lighting for taking pictures of models (that is, trains and silly tabletop games, not the other sort, sorry for the disappointment) I'm looking for a solution that allows me to take passable pictures with my phone without heavy shadow all along one side of a model or the other.

Now, any remotely "professional" lighting is obviously going to cost silly money, and it is far and above what I need. All I'm after is a couple of light diffuser boxes with sufficiently bright lights in them that I can use occasionally. I've found a couple of videos which show how to make these out of cardboard and tin foil, which is well within my abilities, but my ability vanishes as soon as I start to look at the lights themselves.

Apparently, LED brightness is measured in Lumens now, and this is more important than Wattage. Is this the case?

The tutorials I've seen talk about using "60 watt light bulbs" but locally companies seem to be a bit inconsistent about whether a light's output is measured in Lumens or Watts. Given that I'll be using a diffuser, of course, I need a higher output as well.

So, how can I work out a ballpark figure for how powerful the light needs to be? I have a notion of using rechargeable LED building floodlights, because it means I can move them around a game without worrying about cables, but I have no idea if they will have a sufficient output. Some are advertised as having "2000 Lumens" which would be useful if I knew what that meant: is that a bright light, a dim light? Or somewhere in between?

Also, as the specifications seem to change a lot, is there a way of calculating Lumens from Wattage on LED's?

 

[Drago]

The best bit is that there is no industry standard measurement methodology, so the claims of even reputable manufacturers are meaningless when compared to one another as we dont know the methods used to determine the result.

And the Chinese lumen is a work of fiction that makes a politicians word seem truthful.

The only way the be sure is to try a few, easier said than done.

 

[raleighnut]

For some time I've been developing a mildly crackpot idea about improving lighting for taking pictures of models (that is, trains and silly tabletop games, not the other sort, sorry for the disappointment) I'm looking for a solution that allows me to take passable pictures with my phone without heavy shadow all along one side of a model or the other.

Now, any remotely "professional" lighting is obviously going to cost silly money, and it is far and above what I need. All I'm after is a couple of light diffuser boxes with sufficiently bright lights in them that I can use occasionally. I've found a couple of videos which show how to make these out of cardboard and tin foil, which is well within my abilities, but my ability vanishes as soon as I start to look at the lights themselves.

Apparently, LED brightness is measured in Lumens now, and this is more important than Wattage. Is this the case?

The tutorials I've seen talk about using "60 watt light bulbs" but locally companies seem to be a bit inconsistent about whether a light's output is measured in Lumens or Watts. Given that I'll be using a diffuser, of course, I need a higher output as well.

So, how can I work out a ballpark figure for how powerful the light needs to be? I have a notion of using rechargeable LED building floodlights, because it means I can move them around a game without worrying about cables, but I have no idea if they will have a sufficient output. Some are advertised as having "2000 Lumens" which would be useful if I knew what that meant: is that a bright light, a dim light? Or somewhere in between?

Also, as the specifications seem to change a lot, is there a way of calculating Lumens from Wattage on LED's?

Normally printed on the side of the box in UK as in '60w equivalent'

 

[fritz katzenjammer]

Lumens are the metric measure of light output. The newest LEDs can be made to belt out so much light for a given input of power that Watts, as an output measurement, got left behind.

Were I trying to photograph my wee N scale trains I would likely start by borrowing the lighting set from my bicycle as it is portable, powerful and, most importantly, already paid for. The one of them claims 1300 Lumens output and is better on the road than the H4 Halogen headlamp on my old Suzuki, so I don’t doubt it.

 

[Bonefish Blues]

They were fictional characters, penned by Tove Jansson. Looked a bit like hippos, charming creatures.

 

[albion]

Lumens is total light whilst lux is a measure of spot intensity.

Thus light bulbs quote lumens.

 

[oldandslow]

Measuring light is easy till you start thinking about it. At least, that's how I find it. There are some good explanations here and here. And one concentrating on cycle lighting. I think you really want lux, because you're bothered about the light falling on particular parts of your model.

Watts is the power input. If only you could rely on efficiency (in turning that power into light) being roughly constant across bulbs, it would work as a rough measure of light. But, for example, there have been complaints historically that rules about Watts for vehicle lighting were made nonsense as manufacturers produced ever more efficient bulbs, with the result that everyone blinded each other with numbers of Watts that were originally barely sufficient to light up the road.

Lumens is the light coming out of the bulb/source. But, if most of that is not going in the direction you want, it may not be a useful measure. Even if reflectors and the like are directing it, is that appropriately? For mountain biking, you probably want to spread those lumens more widely (to show up overhanging branches and the like) than on the road, where you want a dipped beam focused on the road ahead, so the same lumens in the two cases aren't going to produce the same lux on that patch of road. But, as we all know, the further away the patch of road, the fewer the lux, as the light spreads out more.

So (within reason) the bigger the numbers the better, as long as you are talking about lights that illuminate comparable "patches". I think!

 

[Dogtrousers]

Watts was fine when everyone way using incandescent lightbulbs. Its a measure of the power consumed, not the light emitted. But if everything is a lightbulb then it's a reasonable measure.

The problem is that old light bulbs were inefficient and much of that 60W was wasted as heat. LEDs are more efficient so a LED setup consuming 60W would be putting out way more light than a poxy old 60W bulb. That's why we get labels saying 60W equivalent. It means it puts out as much light as a 60W bulb used to (but consumes a lot less than 60W)

It would have been more sensible all along to have used light output instead power input as a measure. And we've belatedly swapped to that. Lumens are a measure of this. Lux (or the delightfully named imperial equivalent the foot-candle) is a measure of how much light is falling somewhere.

So how much light did a 60W bulb emit? About 800 Lumens according to Google.

 

[andrew_s]

Watts is the electrical energy used to produce the light.

Lumens is the "amount of light" - i.e the radiated energy, weighted according the spectral sensitivity of the human eye. A 100 lumen red light and a 100 lumen green light will look the same brightness, but the former will radiate several times the energy of the latter, because the eye isn't as sensitive to red as it is to green.

Converting watts to lumens depends on both the frequency of the emitted light and on the efficiency of the emitter.
A theoretical 100% efficient light source emitting monochromatic green light at the peak sensitivity of the eye will give 683 lumens per watt.
A 100% efficient light source emitting the various colours that make up white light will give somewhere around 300 lumens per watt.
An old-style tungsten filament light bulb is inefficient because most of the emitted radiation is in the infra-red, which you can't see and hence contributes nothing to the emitted lumens.
The best current LEDs can get up to 200 lumens per watt (though this will be at low power as the efficiency falls as the LED heats up).

The LED light (singular) I'm using in my living room at the moment says on its box: 13.5 W, 1500 lumen, 100W filament bulb eqivalent.

As for what's bright enough for your model photos, you are into the old shutter speed/aperture/ISO trade offs.
Summer daytime sunlight in the UK is about 50,000 lux (lumens per square meter).
The old "sunny 16" rule for photography says that on a sunny day, the shutter speed at f/16 should be the reciprocal of the ISO setting (or film stock), so at ISO 100, 1/100 sec at f/16 is the correct exposure for a sunny day.
So, if you cobble together a 5000 lumen light source and use it to illuminate a 50 cm x 50 cm area of model (with minimal light spill elsewhere), that's 20,000 lux, which would approximate an exposure of 1/100 sec at f/16 using ISO 250. Alternatively, the same light source illuminating 1 sq m will give 5000 lux, needing ISO 1000 for the same shutter speed & aperture.

These are ballpark numbers. In the real world you can reckon on losing at least half the 5000 lumens to light absorbed in the light fitting, or falling outside the desired area of the model.

 

[Reynard]

If you are looking to eliminate harsh shadows from photographs, then you will need to be using multiple light sources. A decent book on film photography (e.g. The 35mm Handbook) will show you how to do that.

Of course, those basic principles will be for flash units slaved to the main one on the camera, but a couple of basic bendy desk lamps with a bell shade and some tissue paper or light cotton fabric taped over them to diffuse the light, plus some white card to act as reflectors (overhead and to the side) should do the trick. The advantage of a bendy desk lamp over a bike light, say, is that the position and direction of the light source is infinitely adjustable.

Oh, and make sure the light bulbs are daylight balanced.

 

[classic33]

Paging @Scaleyback of Little People fame.

 

[Andy in Germany]

If you are looking to eliminate harsh shadows from photographs, then you will need to be using multiple light sources. A decent book on film photography (e.g. The 35mm Handbook) will show you how to do that.

Of course, those basic principles will be for flash units slaved to the main one on the camera, but a couple of basic bendy desk lamps with a bell shade and some tissue paper or light cotton fabric taped over them to diffuse the light, plus some white card to act as reflectors (overhead and to the side) should do the trick. The advantage of a bendy desk lamp over a bike light, say, is that the position and direction of the light source is infinitely adjustable.

Oh, and make sure the light bulbs are daylight balanced.

I probably should have posted this earlier, but this is the sort of idea I'm aiming for:



Two lights to start with, to eliminate shadows. Ideally, I'd like to use cordless building site floodlights because then I can move them.

This is an example of what I'd use them for: notice the main light source is from the left. I got away with this because it was a bright overcast day, but as soon as it is either sunny or goes dark I have shadows everywhere. My goal would be to have a couple of soft lights to remove the shadows.

 

[MichaelW2]

You need diffuse light source.
Simplest is a bit of diffuser over your camera light.
Bouncing off white surface.
Shining through large diffuser.
Diffuser tent.

 

[Yellow Saddle]

Two nice explanations by Ol' Dogpants and Andrew here.

I'll add something just to add to the complexity and that's colour temperature. If you are considering the lights for photography, colour temperature is important because LEDs can be cold (blue, not Celcius) or warm (reddish/orangeish, not hot as in heat). Colour was mentioned by Reynard in passing.

The temperature is displayed on the bulb in Kelvin or K. Typically 2000K or 8000K or something inbetween. The higher the number, the bluer the light. The lower the number, the redder the light. Film/CMOS sensors pick up the colour very much differently from the eye.

Modern cinematographers pay lots of attention to colour and will even have a colour palette they work from. This is very visible in the current Nordic Noir style of drama on TV. I've seen green, yellow and lately, monochrome.

Without getting fancy, your choices will range between ice cold and warm only.

 

[presta]

Two lights to start with, to eliminate shadows. Ideally, I'd like to use cordless building site floodlights because then I can move them.

If you just want to eliminate shadows, one lamp and a reflector will do. You can make one from a sheet of card covered with crumpled cooking foil. When it comes to the colour temperature of the light, bear in mind the same applies to any film/tissue you put across the front of it as well. The reason builders lamps are cheaper than photofloods is that builders don't care about colour temperature.