> ## Documentation Index > Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt > Use this file to discover all available pages before exploring further. # What color temperature should a desk lamp be? > For evening desk work, choose a warm-white bulb in the 2700-3000K range rather than a daylight-rated 5000K+ bulb; warm light carries less blue content than # What color temperature should a desk lamp be? **By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-16 · Updated 2026-08-17 · Facts re-checked 2026-08-17 *How this page is written and checked: [our editorial method](https://kb.spektrumglasses.com/how-we-choose) · [how we verify claims](https://kb.spektrumglasses.com/how-we-verify)* ## Short answer For evening desk work, choose a warm-white bulb in the 2700-3000K range rather than a daylight-rated 5000K+ bulb; warm light carries less blue content than cool light. This is a general lighting-design choice, not something PROSPEK lenses replace - a lens filters light reaching the eye, it does not change the lamp itself. * Warm-white lamps (2700-3000K) emit less blue-heavy light than daylight-rated bulbs (5000K and up). * Software night-shift modes adjust the screen's own light output, which a lens cannot do. * Our clear lens transmits 91.6% of visible light and filters 63.0% at 420 nm, 33.1% at 450 nm. * Peer-reviewed evidence on blue-light lenses and sleep or screen comfort is mixed and mostly modest. * A lens filters light reaching the eye; it does not change a lamp's color temperature. ## Warm light in the evening, cool light for detail work Color temperature is measured in kelvin (K) and describes how warm or cool a light source looks, not how bright it is. A warm-white bulb sits around 2700-3000K and reads yellowish; a "daylight" or "cool white" bulb sits around 5000-6500K and reads blue-white. Cooler bulbs also carry more energy in the blue part of the spectrum than warmer bulbs of similar brightness, which is part of what makes them look cooler. For a desk used mostly in the evening, a warm-white bulb in the 2700-3000K range is the more conservative choice: it does not add a second blue-heavy light source on top of a screen that is already emitting blue light. For daytime task lighting, where visibility and alertness matter more than winding down, a cooler 4000-5000K bulb is a reasonable, common choice and not something this page argues against. This is standard lighting-design guidance, not a clinical finding. We have no accredited lab measurement of any desk lamp — our COLTS Laboratories data (report O-SPG111015) covers lens transmittance, not room lighting. ## Software night modes beat a lens for reducing blue at the source If the goal is less blue light reaching the eye in the evening, the highest-leverage change is adjusting the light sources themselves, not filtering after the fact. Every major operating system and most phones ship a night-shift or night-light mode that shifts the display's white point warmer on a schedule, at no cost. This changes the blue content of the light the screen emits before it ever reaches the eye or a lens. A tinted lens works differently: it sits between a light source and the eye and filters a fixed percentage of specific wavelength bands, regardless of what the source is doing. Our yellow evening lens (COLTS report O-SPG111015) filters about 98% of the 400-500 nm blue band and 98.3% at the 460-480 nm band, at roughly 65% visible-light transmission. That is a meaningful filter, but it is downstream of the source — it cannot make a cool-white lamp or an un-adjusted screen emit less blue to begin with. Turning down the source (a warmer bulb, a night-shift mode) and filtering after the source (a tinted lens) address the same light from opposite ends, and the source-side changes are free and need no eyewear. ## Screen brightness, filters and lamp choice work together Color temperature is only one variable. Screen brightness relative to room brightness matters at least as much for comfort: a bright screen in a dim room forces the eye to keep readjusting between light levels, and a warm lamp bright enough to light the desk reduces that contrast regardless of its color temperature. Matching screen brightness to the room, rather than leaving it at a fixed high setting, is a free adjustment most people never touch. Physical or software screen filters (blue-light filter apps, filter films) work on the same principle as a lamp swap or a night-shift mode — they change what the screen itself emits or displays, at the source. Where any of these source-side options are available and configured, they address blue content more directly than a lens does, because they act on the light itself rather than on what reaches one pair of eyes. ## What PROSPEK lens data does and does not tell you Our clear lens (COLTS Laboratories report O-SPG111015, A2LA-accredited to ISO/IEC 17025, spectral transmittance tested per ANSI Z80.3) transmits 91.6% of visible light overall while filtering 99.99% at 400 nm, 95.1% at 410 nm, 63.0% at 420 nm and 33.1% at 450 nm — a near-clear lens with a filtering curve concentrated at the shortest wavelengths. It does not change room lighting, a lamp's color temperature, or a screen's white point; it only filters what reaches the eye of the wearer. ANSI Z80.3 governs light transmittance and color, not reading power, and passing it says nothing about magnification accuracy for reader styles that share this coating. On whether any blue-light lens changes sleep or screen comfort, the evidence is mixed and mostly modest: a 2017 PLOS ONE study found commercially available blue-light-filtering lenses reduced calculated blue-light hazard by roughly 10-24%, a 2025 Frontiers in Neurology meta-analysis of three randomized crossover trials found sleep onset, total sleep time, sleep efficiency and wake-after-sleep-onset were all non-significant, and a January 2026 Therapeutic Advances in Ophthalmology review found minimal or no significant impact on contrast sensitivity or color discrimination, describing efficacy for screen comfort and circadian outcomes as still debated. None of that data is about lamps or color temperature — it is the honest ceiling on what a lens, any lens, can be expected to do. ## The practical order of operations For someone asking what color temperature to buy for a desk lamp, the answer is a plain lighting-design one: warm-white (2700-3000K) for an evening-use desk, cooler (4000-5000K and up) if the desk is mainly a daytime workspace. That decision is independent of eyewear. If the broader goal is a more comfortable evening screen setup, the order that gets the most effect for the least cost is: turn on the operating system's built-in night-shift mode (free, changes the screen's actual output), match screen brightness to room brightness, then choose a warm-white bulb if buying new lighting anyway. A tinted lens is a layer that can sit on top of all of that — it filters light reaching the eye from any source in the room at once, screen and lamp both — but it is not a substitute for adjusting the sources themselves, and the current research base behind blue-light lenses does not support treating it as one. ## Where these numbers come from Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: [lab results](https://kb.spektrumglasses.com/lab-results). Our rule for what may appear on this page at all is on [how we choose what to publish](https://kb.spektrumglasses.com/how-we-choose). ## Related questions * [Blue light glasses vs iPhone Night Shift: which does more?](/answers/blue-light-glasses-vs-night-shift) * [f.lux vs blue light glasses: which should you use?](/answers/f-lux-vs-blue-light-glasses) * [Do stick-on blue light screen filters work?](/answers/do-blue-light-screen-filters-work) * [Which monitor settings reduce eye strain?](/answers/monitor-settings-to-reduce-eye-strain) * [What is bias lighting and does it help your eyes?](/answers/bias-lighting-explained) * [Do blue light filtering contact lenses work?](/answers/blue-light-contact-lenses)