A desk lamp has one job

A desk lamp exists to light the things on your desk that don’t light themselves — paper, a notebook, a keyboard in a dim room, your hands. That’s the whole job. It is not there to light the screen, which lights itself, and it is not there to light the room.

Get the job wrong and the lamp becomes the brightest object in your field of view, which means you position your head to avoid it. Get the position wrong and it casts a shadow of your own hand across whatever you’re writing on, so you turn your body to get out of your own way. Both are all-day compensations caused by a five-pound object you could move in a second.

Which side it goes on

The rule that resolves most lamp problems: the lamp goes on the opposite side from your writing hand, in front of you rather than behind, and low enough that the bulb is below your eye line.

Opposite side, because a lamp on your writing side puts your hand and pen between the light and the page — you write in your own shadow, and you lean or turn to see. Right-handed means the lamp goes left.

In front rather than behind, because anything behind you reflects in the screen. This is the same principle as where daylight should come from: light from beside and slightly ahead, never over your shoulder.

Below eye line, because a visible bulb or a bright shade in your peripheral vision is glare regardless of what it’s illuminating. If you can see the bright part of the lamp while looking at the screen, lower it, angle it down, or turn it to face the desk surface.

DESK LAMP — the check
  Sit as you work, screen on, lamp on, room light as usual.

  · Can you see the bulb or a bright shade while looking at
    the screen?                          → too high, or aimed wrong
  · Turn the screen off. Is the lamp reflected in it?
                                          → move the lamp, not the head
  · Write something. Does your hand shadow the page?
                                          → lamp is on the wrong side
  · Cover the lamp with your hand for a moment. Does the desk
    go noticeably dark?                    → it's doing a real job
      Nothing changes                      → it's decorative; the
                                             room light is doing it
  Then: is your head level and facing the screen, or tilted?

The last line again. A tilted head is the symptom that lighting problems produce, and it’s easy to attribute it to a monitor.

When you don’t need one at all

Worth saying plainly, because the answer for a lot of setups is that the lamp is optional.

If your work is entirely on screen and the room has reasonable ambient light, a task lamp adds nothing except another light source to manage. The screen lights itself; the keyboard doesn’t need to be seen if you can touch-type; there’s no paper. Adding a bright lamp to that situation makes the brightness relationship worse, not better.

A lamp becomes genuinely useful when:

• There’s paper. Anything you read or write on the desk surface.
• The room is dim and the screen has become the brightest thing in it by a large margin. Here the lamp’s job changes: it isn’t lighting the desk, it’s raising the room so your eyes aren’t jumping between a bright rectangle and a dark surround. For that job it wants to point at a wall or the ceiling, not at the desk.
• You do close work — anything fiddly with your hands.

Those are three different jobs wanting three different lamp positions, which is why one lamp in one place is often unsatisfying and why an adjustable arm is the feature worth having. Not a brand recommendation; a shape recommendation.

Lighting the room versus lighting the desk

These get conflated and they’re opposite tasks.

Lighting the desk wants a directional light, close, aimed down at the surface, bright relative to its immediate surroundings.

Lighting the room wants an indirect light — bounced off a ceiling or a pale wall — so that no single source is much brighter than the others and the wall behind your screen isn’t a dark void.

If you only have one lamp and the room is dim, the room job is usually more valuable than the desk job, because the brightness mismatch between screen and surroundings affects every hour you work while the desk surface only matters when there’s something on it. Point the lamp at the wall behind the monitor. A cheap lamp bounced off a pale wall does this well; an expensive one aimed at your keyboard doesn’t.

Two things not worth worrying about

Colour temperature. Warm or cool light is a preference. There is a great deal of confident content about which colour temperature makes you productive or alert, and it is not something this site is going to assert. Pick the one you like looking at; if you use the desk in the evening, warmer light is generally the more comfortable choice, which is a comfort claim rather than a health one.

Flicker, mostly. Some cheap dimmable fittings flicker perceptibly at low settings, and if you can see it or it’s uncomfortable, don’t use it at that setting. That’s the extent of the practical advice; anything more specific gets into claims about invisible flicker that get repeated far more confidently than the evidence supports.

Where the lamp gets in the way

Physical footprint, which is the part nobody plans for. A lamp with a wide base occupies desk depth, and depth is the dimension you’re usually short of. On a shallow desk, a clamp-mounted lamp or one that mounts to the wall or a shelf gets the base off the surface entirely, the same way a monitor arm does — see desk depth for why that’s worth more than it sounds.

Cable, too. A lamp cable running across the desk and down the front is one more thing to catch on, and lamp cables are notorious for ending up in the footwell, where they restrict your feet more effectively than any solid object.

What light doesn’t fix

Good light removes a reason to tilt your head and squint. It doesn’t treat anything, and a well-lit desk you sit at for four unbroken hours will still leave you stiff — duration does that, and getting up is a different subject from furniture.

Tired eyes after a screen day are ordinary. Persistent headaches, eye pain, or any change in vision are reasons to see a qualified professional — an optician first, in most cases — rather than reasons to rearrange a lamp. Straining to read a screen is frequently an uncorrected-vision problem wearing a lighting costume, and no lamp substitutes for an eye test.

Move it to your non-writing side and drop it below your eye line. That’s most of it.