About this specific Prism model:
This lamp is pretty well made of quality plastic and aluminum parts painted to match. The design is pretty good in general, but with a serious mechanical design flaw: the lighted arm of the lamp is held into the pivoting hub by friction and two tiny screws through two small tabs in the translucent plastic diffuser that forms the underside of the lighted lamp arm. The lamp reached me with both of those tiny plastic tabs broken off, and the lighted arm separated completely from the lamp. This allowed me to inspect the construction of the lighted arm: clean and solid, with well-thought-out LED placement discussed below. The lighted arm was electrically connected to the rest of the lamp with a small plug that had pulled out when the arm separated from the rest of the lamp. I reconnected this plug and pressed the arm back into its socket to get a good idea of how the lamp functions. I considered keeping it even in this condition, but decided not to because the arm tended to droop without the screws to hold it in position, and because the basic configuration of this lamp (and most of the others similar to it) does not work well on a desk with a computer monitor. I suspect that this lamp is vulnerable to the damage that I saw from expectable accidents in ordinary use.
This lamp changes both brightness and color temperature continuously from more orange than you probably want (3500 degrees Kelvin, according to the manufacturer) to more blue than you probably want (5500 Kelvin) by rotating the far end of the pivoting arm. You can leave it at one color setting and turn it on or off with a touch sensor at the far end of the arm another nice bit of design. The lighted part of the arm has an array of small, bright surface-mounted LEDs in a single line along the middle part of the arm, and two parallel lines at each end. The array is a mixture of warmer (more orange) LEDs and cooler (more blue) LEDs. The color adjustment works by adjusting the brightness of the two colors, from only the warm LEDs on at the warmest setting, through all of the LEDs on at maximum brightness and intermediate color, to only the cool LEDs on at the coolest setting. A mid-range setting, with all of the LEDs at maximum brightness, is both the brightest and the most pleasant white color, to my taste (that would be about 4500 K, according to the manufacturer's color/brightness chart). The brightness is plenty for a good desk task lamp, but not enough to light a room. The arrangement of the LEDs and the housing produces light of uniform color and brightness on the desk below the lighted arm. When the arm is horizontal, parallel to the desktop, the brightly lit area is about 30 inches wide (15 inches on either side of the arm), and extends from the base of the lamp to maybe 6 inches beyond the end of the arm. Beyond those limits, the brightness tapers off gradually.
About LED desk lamps in general:
Some other LED lamp designs use one or a few high-wattage LEDs. This approach tends to produce one or more sets of sharp, irritating shadows. Think of sharp shadows of the hairs on your wrist cast on the paper you are writing on. This Prism lamp and other LED lamp designs with a long array of many lower-wattage LEDs produce a much more diffuse, but still bright, light that is free of harsh shadows. That is much better, in my view.
The basic problem with lighted-arm LED desk lamps:
There is a fundamental problem with all of these illuminated-arm LED lights, of which there are numerous on the market: the arm has to be directly above the lighted area. If you place the lamp base at the back of your desk, you will have the arm pointing at your head, just below eye level (so the LED's don't glare in your eyes), and ending maybe a foot from your face, in order to illuminate the desk in front of you. If you move the base to one side along the back of the desk, you can angle the arm so it is pointing over your shoulder on the opposite side, but it still has to come close to you in order to illuminate your working area. At best, you can stand the base of the lamp 15 or 20 inches in from the front of your desk, and run the arm crosswise to your direction of view, parallel to the front of the desk. I still find the arm irritatingly close to my face in that arrangement, but the real deal-breaker is that any of these arrangements ends up with the arm of the lamp blocking your view of your computer monitor. The lamp's pivot is simply not high enough for the arm to be above the top edge of your monitor. So you either have the lamp pointing in your face on one side of the monitor (and illuminating the desk mostly to one side of the monitor, not in front of it), or you have stand the lamp on something to raise it up so you can see under it to your monitor, which then exposes your eyes to the glaring LEDs... to you have to rotate the arm so that it aims the light not down, but more towards the back of the desk in order to shade your eyes... but them you have to move the arm even closer to your face in order to illuminate the closest part of your working area. These problems could be reduced with a lamp design that had a higher pivot point, a longer lighted arm, and the LEDs recessed more deeply in the arm to block a direct view of them from the side.
The only lighted-arm LED lamp I have seen that appears to solve these problems is the Koncept AR3000, which I inspected in the flesh at a local lamp store. It does not have the adjustable color feature of the Prism, although you can buy either a warmer-color or cooler-color version. It appears to be comparably bright. Its physical design involves an additional arm and joint, and the arms are sufficiently long to allow the lighted arm to be placed parallel to the front edge of the desk, high enough to be above the monitor and not block your view of it, and angled enough not to glare in your eyes. (Koncept makes some smaller models that look similar, but are too small to illuminate in front of your monitor without blocking your view of it.) The design is very light, clean, and high-tech, and the lamps appear to be well made... but the price, well over $300 for a desk lamp, is a bit hard to swallow. I also wonder how long the tiny plastic joints will stay tight. If they loosen, this lamp would become an irritating frustration.
My solution:
I am now happy with a completely different LED approach. I clamped an old full-sized swing-arm architect's lamp to the edge of my desk and screwed in a bright LED bulb. I am using a Thetalux 9 watt cool white 5000K 700 lumens dimmable A19 screw base LED bulb, which is a direct replacement for a standard 75-watt incandescent bulb in every respect except that it is much heavier. The architect's lamp lets me position the head and aim the light anywhere; it can light my whole desk or even the room moderately brightly if I point it at the wall and ceiling, or dimly for using a projector or watching movies by swinging the head down below the edge of the desk, aimed at the floor. The bulb is recessed in the reflector deeply enough to prevent glare from a direct view of the bulb. The bulb's light is bright but diffuse, and is further diffused by the lamp's reflector, so there is plenty of light without harsh shadows. Subjectively, the total light output seems much greater than that of the Prism lamp, which already wasn't bad for a desk lamp. I can easily position the lamp to light the desk without obscuring my view of the monitor or casting glare on it. I can push the lamp out of the way when I want to. To my surprise, the architect's lamp looks fairly light and unobtrusive, even compared to the more modernistic but squatter Prism, especially since most LED desk lamps have a large, flat base that takes up desk space and has a large visual mass, rather than clamping to the edge of the desk as most architect's lamps do. One caution: you want a real, full-sized architect's lamp for this, such as you would find in a graphic arts store, as opposed to the smaller, more retro-design-oriented ones also available online or at places like Ikea.
Even if you have to buy a cheap but functional architect's lamp, this solution will cost much less than any decent LED desk lamp, and it works much better.
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The problem with most L.E.D. lights is that they produce a harshly unpleasant "blue-white" light, similar to most fluorescent lights. This is often called "crisp white" or "bright white", and it is anywhere from 3,500 degrees Kelvin (somewhat unpleasant) up to 5,000 degrees Kelvin (very unpleasant). While this light is capable to producing that type of blue-white crisp / bright white color of light... with the simple turn of the light-color-dial... you can adjust it down to a much more pleasant incandescent-bulb-like "warm white" color of light (slightly amber-colored) in the 2,500 to 3,000 degrees Kelvin range. This makes for a very versatile, efficient, silent, cool-to-the-touch, pleasant desk lamp.
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