Light and lighting

Often (including in the Habré), the question of lighting, especially the “nanotechnological” LED , comes up, and the shit wars of the holy “led” against luminescent lamps often begin to fumigate. For more than a year I was about to write an article about light, and it finally happened.

From this article you will find out why in photo studios they do not take pictures with fluorescent lamps, why LEDs have not yet taken over the world and whether it is worth illuminating the streets with them. Go!

About color and spectrum

We all know that our vision is primitive, three-component: we have three types of “color” receptors - “red”, “blue” and “green”.



But life is usually more difficult - the color is determined by the long wave / energy of a quantum of light, and it is like a double, it takes any values. Accordingly, a quantum of light can fly into our eyes in the middle between red and green, and red and green receptor types will react to it "in half". From here come various “incomprehensible” color blends - if the object reflects both red and green light, then we will see yellow, although in fact there are no quanta with a “yellow” wavelength.

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To make it clearer: the eye can not distinguish if the object reflects a purely yellow light (580nm), or both green (520nm) and red (680nm). In the eye, both receptors are activated in both cases and we will see the same color, yellow.



The reality is much more complicated than just RGB. Hence all these problems with “color profiles”, “white balance”, “wrong lighting”

About bad lighting

If any of you were engaged in printing a photo of a house with a red lamp, you might have noticed that all the objects that do not reflect the red light in the light of the red lamp seem black. It does not matter that they reflect green or blue light well, since there is no red, it means that the object reflects nothing, i.e. the black. From here it should be clear from what color distortions may appear at all, but to this a little later.

Main characteristics of lamps

1. Efficiency, lm / W (= how much of the visible light gives the lamp at 1W of power).

2. Lifetime / Reliability

3. Quality of lighting (spectrum, flicker)

The main types of lamps

In this article we confine ourselves only to the fact that it is widely used for lighting, information on any specifics like xenon arc lamps can be found yourself know where :-)



1. Incandescent bulbs

Historically the first type of lamps. Awful energy efficiency - 8-10 lm / W. The main problem with reliability is during power up. Those. the filament resistance is lower, the lower the temperature, when turned on, the lamp wakes up to 10x of nominal power, and due to ultrafast heating, the filament is gradually damaged. When working through a protective device, which turns on the lamp "slowly" (in the simplest case - a thermistor), the service life can be very long. Spectrum - continuous (almost the spectrum of a black body), with a shift to the red region. Currently, all indicators lose more modern types of lamps.



2. Halogen lamps

In fact, this is also an incandescent lamp, but bromine or iodine is added to the flask, which increases the service life and allows you to raise the temperature of the filament. The energy efficiency is slightly better - 10-15 lm / W, the spectrum is also continuous and also shifted to the red region, but less. The only almost ideal source of light for photography (only xenon flash lamps are remotely comparable with it, but the spectrum is no longer even, with a strongly protruding blue part, especially at 480nm). Also, if there is a soft start mechanism, the service life can be very long (without it, depending on the number of on / off).



The main thing to remember is: if the room is heated by electricity, then putting “energy-saving” (fluorescent) lamps there to save energy does not make sense at all, you will have to spend as much more energy for additional heating, or it will be just colder.



3. Fluorescent lamps

In fluorescent lamps, the discharge in mercury vapor (of which there is a few milligrams in the lamp) is produced by ultraviolet light, which the phosphor re-emits in the visible range. Contrary to attempts to fan the tantrum, hard ultraviolet cannot in serious quantities get out of the lamp - because The case of ordinary glass does not let ultraviolet light through, and what remains is much less than the solar level. In order for the ultraviolet to go out - you need a body made of quartz glass, but it is very expensive, by mistake it will not slip .



The main groups 2: "long" and "compact, in the standard base." The difference - in the long no electronics, it is part of the lamp. In the compact - as an electronics worth low-quality Chinese crafts that often burn out faster than the lamp itself. Of course, there are compact lamps and with normal electronics, soft start and so on. - but they cost a lot (throwing electronics out with each lamp ... where the greenpeace is looking), and they don’t do that much. China is winning. On the right is just a sample of the electronics from the lamp that is thrown out with each lamp (photo from here ). By the way, this electronics (ballast) can be powered by long lamps of similar power, although this is not the most reliable solution - after all, all the components here are the cheapest and the lowest quality ones.



Energy efficiency compact - from 50 to 70 Lm / Watt (this is still the best that Phillips has).



Reliability depends on temperature, electronics, and workmanship in general. If you have the ceiling lamp looking down, so that hot air cannot go anywhere - the lamp will die very quickly. Drilling holes throughout the plastic housing helps. Also, the electronic part can be repaired - in many cases a capacitor simply flows there, which can be replaced with a similar one (repair is more than relevant for high-power lamps). Because these lamps make for mere mortals, finding the data on the spectrum is not so simple, and it can be assumed that the cheapest and simplest phosphor is used - after all, it is necessary to save the cost for the electronic part of the lamp.



“Long” lamps are much more interesting, efficiency from 50-65 Lm / Watt (with a more “pleasant” spectrum) to 100-110 with a “bad” spectrum, this is taking into account electronics. In any case, due to the fact that the electronics are not thrown away, at a lower cost, the lamps last longer. Also on the Philips website for any direct lamp, you can safely look at its spectrum and see how close it is to the sun.



Now more about the spectrum - it is far from even. In the spectrum of an energy-efficient luminescent lamp (with a “bad” spectrum, from above) - for example, it can be seen that where our eye is most sensitive (530-550nm) - the failure is almost 0. (Therefore, it cannot be said that 10W of the luminous lamp = 50W of the incandescent lamp) . Hence the distortion of light: if there is an object in the room that reflects mainly light with a wavelength of 530nm, it will look much darker (almost black), much less saturated.



In reality, objects rarely reflect one particular wavelength, because the RGB ratio will simply change compared to daylight, and many things will be darker / less saturated than in daylight.



Lamps with a “good” spectrum, although they have peaks, still do not have such hard failures - but for this they had to pay twice the worst light output at equal power.

Service life - depends on temperature and quality of electronics (ballast). Normal ballast has a smooth start for extended life, and operates at a high frequency (= no flicker). The buzz from the ancient ballasts with starters and flicker in modern lamps is no longer.



In field conditions, the quality of the phosphor of the lamp can be checked with a compact disc - we look at the rainbow from the lamp on the disk. If the "rainbow" of the bands - shitty phosphor (3 bands - more crappy, 5 bands - a little less). On a lamp with a good phosphor the rainbow will be continuous. But such compact lamps, I think not to find.



4. LED lamps

The cheapest (only on such lamps do) white LEDs are blue + yellow phosphor, which gives a semblance of white light, but in fact is far from white.



Pronounced peaks at 450 and 550 nm, with a dip of about 500, and after 600 nm. Accordingly, with LED lighting, colors will also be distorted.



The best ready-made LED lamps give energy efficiency at the start of service 50-60 Lm / W (that is, less than the best fluorescent ones, about as much as compact fluorescent ones). They cannot have great power, because they die very quickly when overheated. Lifetime is highly dependent on temperature, and in any case not higher than 50'000 hours (at half power and with good cooling, of course, maybe more). If the lamp overheats to 100 ° C, it will die in units / tens of hours. But frequent switching on / off doesn’t harm them at all.



If you buy LEDs separately, firstly it will be difficult to find the right LEDs with good light output. At the factory, they are immediately beaten into categories, and the most effective ones sell more expensive. And often what is available in stores is one of the worst episodes, with an efficiency of 30-40 Lm / W. Next, you need an efficient power supply (with a stabilized current, not a voltage), a horseradish power supply with an efficiency of 75% will easily impair the light output almost to the level of halogen lamps :-)



For many years I was tormented by the question, why it is impossible to supply the LEDs with stabilized voltage, if you pick it up very accurately, so that the current is right? The fact is that when heated, the “resistance” of the diode will change greatly, and at the same voltage the current can go through much less or more than the norm, and the diode quickly degrades (if the current is 2 times higher, they do not immediately burn out, just service life is 1000 times less. Light output per watt by the way quickly falls, therefore there will be almost no additional light, everything will go to heat).



Taking into account all the above, to do the main lighting with LEDs, especially with their price - complete insanity, and the situation in the coming years will not change quickly. The advantages are only when working in conditions of vibration (lights, transport) and frequent on / off (toilet).



5. Sodium lamps

Sodium lamps - can be seen in street lighting. They have phenomenal efficiency, usually 100-150, up to 200 Lm / W (yes, 4 times more efficient than the best LED lamps, and 2 times better than the most efficient fluorescent ones), cost a penny.



The only problem is that they shine with a yellow light, and no one else, because they can only illuminate the streets, warehouses and so on. Anything that does not reflect the yellow light will be black.

Lifetime - tens of thousands of hours, the price - a penny. In light of this, we can only say that the installation of LED street lighting is a complete drink of dough. There is nothing more efficient and cheaper than sodium lamps for street lighting.



6. Metal halide lamps with ceramic burner

These lamps are light exotic. With an efficiency of about 100 lm / W, with a spectrum without major dips, but quite expensive. In all respects, except for the price, they are better than fluorescent ones, and it is on their basis that I collect an edged chandelier in my room. There is a quartz burner - there is a worse spectrum. You can google with the keyword CDM-TD or on the Philips website.

Conclusion

The moral of the story is:

• In the toilet and lanterns buy LED lamps (not afraid of shaking, on / off).
• The main lighting in the room where work is going on is fluorescent with a “good” spectrum (checking on the manufacturer’s website, if there is no information, then everything is bad ). Better "long" if you find the right fixtures.
• Lighting in rooms where you do not need to work - energy-efficient fluorescent lamps with poor spectrum (or with good, if the electricity is not sorry). Better "long" if you find the right fixtures.
• Lighting in the streets and warehouses - sodium lamps.
• Photography - only halogen lamps (500W lamps with halogen sticks cost a penny). (We don’t say anything about flashlights here, they are certainly not bad)
• Conventional incandescent lamps - only for a rainy day.

Comments / questions / opinions - in the studio!