Light and lighting

Often (including on the hub) the question of lighting pops up, especially the "nanotechnological" LED and often shit of holy wars, the "LED" against fluorescent lamps begin to knock. For more than a year I was about to write an article about light, and it finally happened.
From this article you will learn why photostudios do not shoot with fluorescent lamps, why LEDs have not yet captured the world and whether it is worth lighting 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 complicated - the color is determined by the long wavelength / energy of the quantum of light, and it - as a double, takes on any value. Accordingly, a quantum of light in the middle between red and green can fly into our eyes, and the red and green types of receptors will react to it “in half”. This is where various “obscure” color mixtures come from - if an object reflects both red and green light, then we will see yellow, although in fact there are no quanta with a “yellow” wavelength.

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

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

About defective lighting

If one of you was printing a photograph of a house with a red lamp - you might have noticed that all objects that do not reflect red light in the light of a red lamp - appear black. It does not matter that they reflect green or blue light well, if there is no red, then the object does not reflect anything, i.e. the black. From here it should be clear from what color distortion may occur at all, but to this a little later.

The main characteristics of the lamps

1. Efficiency, lm / W (= how much visible light the lamp gives out at 1W of power).
2. Service life / reliability
3. Lighting quality (spectrum, flicker)

The main types of lamps

In this article we restrict ourselves only to what is widely used for lighting, information on any specifics like xenon arc lamps can be found by yourself you know where :-)

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

2. Halogen lamps
In fact, these are also incandescent lamps, but bromine or iodine is added to the flask, which increases the service life and allows you to raise the temperature of the thread. Energy efficiency is slightly better - 10-15 lm / W, the spectrum is also continuous and also shifted to the red region, but already less. The only practically ideal light source 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, with a soft start mechanism, the service life can be very long (without it, depending on the number of on / off switches).

The main thing to remember: 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 just be colder.

3. Fluorescent lamps
In fluorescent lamps, a discharge in vapor of mercury (of which there are a few milligrams in the lamp) gives ultraviolet light, which the phosphor re-emits in the visible range. Despite attempts to inflate a tantrum, hard ultraviolet light cannot get out of the lamp in serious amounts - because A case made of ordinary glass does not allow ultraviolet light to pass through, and what remains is much less than the solar level. In order for the ultraviolet to come out - you need a case made of quartz glass, but it is very expensive, they will not slip it by mistake .

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

The energy efficiency of compact ones is from 50 to 70 Lm / W (these are the best Phillips have).

Reliability - depends on temperature, electronics, and workmanship in general. If your lampshade looks “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 just flows there, which can be replaced by a similar one (repair is more than relevant for high power lamps). Because These lamps are made for mere mortals, it is not so easy to find data on the spectrum, and we can assume that the cheapest and simplest phosphor is used - because you need to save cost for the electronic part of the lamp.

"Long" lamps are much more interesting, the efficiency is from 50-65 Lm / W (with a more "pleasant" spectrum) to 100-110 with a "bad" spectrum, this is taking into account the 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 see 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 fluorescent lamp (with a "poor" spectrum, on top) - for example, it can be seen that where our eye is most sensitive (530-550nm) - a dip is almost to 0. (Therefore, one cannot say 10W fluorescent lamps = 50W incandescent lamps) . Hence the distortion of light: if there is an object in the room that reflects mainly light with a wavelength of 530 nm - it will look much darker (almost black), much less saturated.

In reality, objects rarely reflect one specific wavelength, because simply the RGB ratio will 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 they had to pay twice the worst light output with equal power.
Service life - depends on the temperature and quality of the electronics (ballast). Normal ballast has a soft start to extend service life, and operates at high frequency (= no flicker). Buzzes from ancient throttle ballasts with starters and flicker in modern lamps are no more.

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

4. LED bulbs
The cheapest (only such lamps are made) are white LEDs - blue + yellow phosphor, which gives a semblance of white light, but in fact it is far from white.

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

The best ready-made LED lamps give energy efficiency at the beginning of the service 50-60 Lm / W (i.e. less than the best fluorescent, about as much as compact fluorescent). They can’t have much power, because they die very quickly when overheated. Service life is highly dependent on temperature, and in any case, no more than 50'000 hours (at half power and with good cooling, of course, it can be longer). If the lamp overheats to 100С - then it will die in units / tens of hours. But frequent turning on / off does not harm them at all.

If you buy LEDs separately, then 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 are sold at a higher price. And often what is available in stores is from the worst series, with an efficiency of 30-40 Lm / W. Next, you need efficient power supply (with a stabilized current, not voltage), a bad horseradish power supply with an efficiency of 75% will easily degrade the light output almost to the level of halogen lamps :-)

For many years I was tormented by the question of why it is impossible to power the LEDs with stabilized voltage, if you select it very accurately so that the required current is available? The fact is that during heating the “resistance” of the diode will change greatly, and at the same voltage, current can go through it much less or much more than normal, and the diode will quickly degrade (when the current is 2 times higher, they don’t immediately burn, just the service life is 1000 times less. Luminous efficiency per watt by the way quickly drops, because there will be almost no additional light, everything will go into heat).

With all that said, doing basic lighting on LEDs, especially at their price, is completely insane, and the situation will not change quickly in the coming years. There are advantages only when working in conditions of vibration (lights, vehicles) 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 effective than the best LED lamps, and 2 times better than the most effective fluorescent), they cost a penny.

The only problem is that they shine with a yellow light, and no more, because they can only be illuminated with streets, warehouses and so on. Anything that does not reflect yellow light will be black.
The service life is tens of thousands of hours, the price is a penny. In light of this, we can only say that the installation of LED street lighting is a complete drank dough. There is nothing more efficient and cheaper than sodium lamps for street lighting.

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

Conclusion

The moral of the story is this:

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

Comments / questions / opinions - in the studio!