All Done With Mirrors....

[bufo marinus]

The lumen formally derives from the candle, based on a light of simple wavelength. A lamp of several wavelength has an exit of lumens which is calculated from the watts emitted as the radiation multiplied by the luminous efficiency in each wavelength, as it was described in the case of the candle.

 

The designer needs to translate the values of cd into Luminous Energy which reaches an object to a certain distance from the lamp. It is this energy which makes the object visible and which turns pale its nuances of color. The energy density which reaches the object is expressed in lumens per square meter (Lm/m²), what is known as lux.

 

This value can be easily calculated from the diagram by a starting point. The candle value (300cd) given by 60° is the same that 300 lumens flowing in the cone of a steradian (sr), that by definition takes up 1m² of the surface of 1m diameter sphere.

 

 

If our object were in that distance, it would be receiving 300 lm/m².

 

In order to deduce the value of any other distance, the same rule must be used in the reverse way. As far as 3m of the lamp, the flux over 1m² declines to 1/9 from the 300lm. The lux value is 33.

 

The illuminance (E) is the lighting flux that falls on a surface, divide by the size of such surface (s). The illuminance is the magnitude of assessment of the light level of a surface or of a spatial zone.

 

 

Its unit of measure is the Lux (Lx), equivalent to the light which falls on each m² of a surface and on which a lighting flux of a lumen is distributed uniformly.

 

 

The illuminance depends on the distance from the focus to the lighted object. It is something similar to what happens when we listen to a car moving away; at the beginning we can hear it loud and clear, but later it decreases until it gets lost. What happens with the illuminance is known as the reverse law of the squares which relates the lighting intensity and the distance to the source. This law is only valid if the direction of the ray of incidental light is perpendicular to the surface.

 

 

Reverse law of squares:

 

In case the ray of light that falls on isn't perpendicular, we have to break up the illuminance to the surface in an horizontal and vertical component.

 

 

The horizontal component of the lighting (EH) is known as the cosine law. It isn't difficult to see that if = 0 we have the inverted law of the squares. If we express EH y EV depending on the distance of the focus to the surface (h) we have:

 

 

Normally, if a point is being lighted by more than a lamp, its total lighting is the sum of the received light.

 

 

 

So, even though Einstein sought but failed to find a unification theory that governed all matter, we have bufo's unification theory on flourescents it goes something like this,

What happens with the illuminance is known as the reverse law of the squares which relates the lighting intensity and the distance to the source.

+ add to this I think you need ummmm around 6000-8000 lux minimum to flower Cannabis + add to this the already low luminous intensity levels of compact flourescents = 5/8ths of fuck all

 

Over to you Bob,......

 

 

 

 

* http://www.dcmsistemes.com/medidasi.html

 

* Also, I salute ANY PERSON who grows their own

[brick]

If we all thought like you the world would still be flat -

Statements like " doesn't mean it's necessarily much higher in luminous intensity " demonstrate your level of comprehension of the concept. You're saying that 2 lights is not better than one? Do some research and then have an informed opinion perhaps.

Why to lights use a Fresnel lens? Do you understand Fresnel's theory? That's next on our agenda. Amplified and reflected from a low power use source. 'Tribalists' who still watch V8 super car racing have little concept that there are many 4 cylinder cars that shit on V8's because they have more 'power' in 8 pistons

looking forward to some wisdom and not unfounded bullshit here - By the way we have the same plants in another location under HID to compare. This is get of ya arse and research stuff - Not a stoned keyboard puncher having delusions of the real world.

Over to you

Cheers

 

Yeah but the V8's sound like a real car not like a baby farting.

[BaronS]

NOTE: (not just but particularly to Bufo) Does this stand scrutiny?

 

The inverse square law is only pertinent for unconstrained space where the area increases as a square of distance.

 

Imagine a perfect reflector (100%) arranged around the four sides of the smaller square and extending to the same area at the greater distance, all light hitting the smaller square also arrives at the surface at the greater distance but is constrained by our reflector to fall on the same area.

 

Sure, we have some losses from reflection. If figures quoted to this thread are to be believed maybe 1-3% at each reflection point, but all the light which hits the first plane hits exactly the same area on the 2nd plane, except our small losses. How much variance in light intensity?

[Frazz]

the inverse-square law is a sensible one to try because it is the way in which anything thins out if it sprouts straight lines from a source and continues out without getting lost ... at double the distance, the same light spreading out through clear air without being absorbed falls on four times the area at double the distance but gives only a quarter of the illumination ..

 

btw great post bufo

 

[BaronS]

and actually, thinking about all this reflection has made me form a hypothesis about why not to use mirrors. What is fundamentally different between mirrors and other reflective choices (mylar, white paint, alfoil)?

 

A mirror reflects a cohesive beam, that's why you can see yourself looking at a 95+% reflective mirror whereas you cannot see your image when looking at 95+% reflective white paint. It is also the reason you can sortta see a reflection on the shiny side of alfoil but the reflection on the rough side is harder to imagine as an image.

 

I think most of us can imagine a box with 6 reflective sides.

 

For sides with 'coherent reflection' if we put a light source in there a pattern will form, the interference pattern of the emitted vs reflected light. This results in hotspots and cool spots, but appreciate that we are not talking about HEAT, these are areas of high and low light intensity due to the action of light acting as a wave and emitted vs reflected waves.

 

NOTE: PLS don't complain that the theory is getting into Physics, I'm madly trying to avoid moving into Quantum Mechanics.

 

So we make our reflective surfaces out of material which has a high reflectivity but low reflective coherence, something that scatters the light. Panda film, the rough side of alfoil, white paint and mylar all have low coherence.

[BaronS]

the inverse-square law is a sensible one to try because it is the way in which anything thins out if it sprouts straight lines from a source and continues out without getting lost ... at double the distance, the same light spreading out through clear air without being absorbed falls on four times the area at double the distance but gives only a quarter of the illumination ..

 

btw great post bufo

 

 

but our light is constrained, not allowed to spread out through clear air without being absorbed but (mostly) reflected back into our area.

[Frazz]

but our light is constrained, not allowed to spread out through clear air without being absorbed but (mostly) reflected back into our area.

 

dammit i thought i had that one all nailed down

 

[BaronS]

further thought therefore allows me to acknowledge SeaHippies' use of mirrors in the manner he/she has. SeaHippies is only using 2 mirrors and they are positioned at 90o to each other, minimal interference pattern, minimal standing waves, minimal hot/cool spots. The area prone to such interference could be pretty well defined by drawing straight lines from the lamp to the edges of the mirrors, and defining the area where reflected and emitted waves cross, in which case you could avoid putting plants into the interference area.

 

Of course, using a material with the same reflectivity but more scatter eliminates the minimal bits and allows the area of the room that is serviced by both emitted and reflected light to have an even distribution of such and therefore be usable growing space.

[bufo marinus]

We could argue the schemantics of the science involved here for years, maybe even decades, lives could be lost, possibly even armed conflict could result, but lets just have a pipe and a look at the logistics instead.

We're talking about reflected light.

I don't recall saying reflected light isn't useful or doesn't add to a greater amount of total light or even that reflected light off mirrors is somehow a bad thing?? I do recall saying why bother and why bother re-inventing the wheel, just a lil joke designed to break the ice and stimulate some debate, not cause a shit fight to see who's the biggest and baddest internet gangster with the best Google links.

Flat white paint has been proven (buy a lux meter from Dick Smiths and take some readings for yourself) to be as good as anything when it comes to how well a surface reflects available light. The fact is that it is an inverse proportion of ever decreasing luminous intensity that is being recouped from an already low level source of light is the only point I was trying to make.

If reflected light wasn't useful we would have no need for reflectors.

If you feel the need for this science to be made re-available to the masses by all means go ahead, no one is stopping anyone from posting or having an opinion

Personally from readings I have taken with my own lux meter before the thievin mo-fo coppers stole it, Adjusta-shades are the best compromise for 2 reasons;

1. The double curve(parabola?) reflector. 2. It's painted with a semi-gloss enamel white paint. This is where discussion needs to start from if you want to start talking anything new

 

How much more luminous intensity will be gained from a flouro grow with the addition of a better reflector/surface, that's what I'd be proving, and the easiest way to shut me up is to take some readings

[SeaHiPPieS]

NOTE: The thread I pointed to ain't my (pathetic) grow, it was simply coincidental that I had opened that thread 5 minutes before reading the recent parts of this one.

 

Though not the chunkiest heads ever to bless our gardens I'd be quite happy pullin gear out of a small grow that, a few days ago, possibly quick dried, smoked OK and is now of that size.

 

Comparing costs of ~250W HID vs CFL

 

CFL needs two lamp holders vs 1 for a 250W HID.

You can probably get 3 130W CFL lamos for the price of 1 250W HID.

CFL lamps have the ballast built in, vs HID separate ballast.

 

The power consumption of a CFL is stated on the device.

The power consumption of HID must include the, possibly as low as 80%, efficiency of the ballast. A 250W ballast will _probably_ draw 310W. (.8*310 = 250)

 

This idea of 'penetration' interests me, and I have read much discussion. Nowhere in any such discussion has anyone suggested how HID produces 'strong' photons, vs CFL's 'weak' photons. Anyone that can show me _any_ science about strong vs weak photons will earn my undying respect.

 

EDIT: forgot HEAT

The HID system will probably also draw additional power because it needs additional ventilation to cater for the heat. Having my own current problems relating to both fresh air and heat dispersal I'll hapilly agree that both systems require adequate ventilation but how much is both startup and running cost affected?

 

Most of the validity for CFL also relates to small spaces.

 

Thank you mate

this is a very constructive post and relates directly to the experiment - Thank you for the input - it is educational