Illuminated frame glossary: lighting and framing terms, A to Z
Most illuminated frame specs come down to four questions: how the light reaches the picture (backlit, edge-lit, LED neon or halo), what the light looks like (Kelvin, CRI, TM-30), how much light and power there is (lumens, lux, watts), and how it is powered and controlled (5 V or 12 V, USB-C, driver, dimmer, remote). This glossary defines each term in a sentence or two and links to the guide that goes deeper.
This illuminated frame glossary explains the words you meet on spec sheets and product pages for lit frames, light boxes and LED displays. Each entry gives a short, plain definition and, where it helps, a link to the guide that goes deeper. For the big picture first, read what an illuminated frame is.
How to use this illuminated frame glossary
Terms are listed A to Z. The diagram shows where the main parts sit in a typical frame, and the table below lists the units you will see most often.
| Unit | What it measures | Where you see it |
|---|---|---|
| K (kelvin) | Color of white light | “2700–6500 K tunable white” |
| CRI (0–100) | How faithfully colors show | “CRI 90+” |
| lm (lumen) | Total light from a source | LED and bulb packaging |
| lx (lux) | Light landing on a surface | Conservation guidance |
| V (volt) | Electrical pressure | “12 V DC adapter” |
| W (watt) | Power drawn | Energy use and running cost |
A to C
Accent lighting
Light that picks out a single feature, like a painting, a shelf or an alcove, so it stands out from the room around it. A lit frame is a compact form of accent lighting. See what accent lighting is.
Acrylic (PMMA)
Poly(methyl methacrylate), a clear plastic sold under names such as Plexiglas, Perspex and Lucite. It is often used as a lightweight or shatter-resistant alternative to glass, for glazing, diffusers and light guide panels. Plain PMMA blocks UV only below about 300 nm, so UV-filtering grades add protection.
Backlit
Lit from behind: LEDs sit behind the artwork and shine through it, with a diffuser in between to blend the light. It suits translucent prints and posters. Compare it with edge-lit in our edge-lit vs backlit guide.
CCT (color temperature)
Correlated color temperature: whether a white light looks warm (yellowish) or cool (bluish), given in kelvins. According to the Northeast Document Conservation Center (NEDCC), the museum community has long favored warm light of 2800–3000 K at low light levels, and CCT is a purely aesthetic choice with no bearing on light damage. See the best color temperature for art.
CRI
Color rendering index: a score out of 100 for how accurately a light shows colors, measured against a natural or standard light. NEDCC notes that museum lighting designers suggest 80 to 100. Lumi Frames’ own specs list CRI 90+ for the Lightbox and 92+ for the Neon.
D to F
Diffuser
A frosted sheet, film or tube that scatters light so you see an even glow instead of separate LED dots. In LED neon, the frosted channel is the diffuser.
Dimmer
A control that lowers brightness, whether it is a knob on the cable, a remote or an app. LED dimmers usually work by switching the LEDs on and off very fast (see PWM flicker) or by lowering the current.
Double-sided poster
A poster printed on both sides, with a reversed copy of the image on the back, so colors look deeper when it is lit from behind. See double-sided movie posters.
Driver
The electronics that turn incoming power into the steady low-voltage supply LEDs need, often handling dimming too. Wikipedia notes that an LED strip’s power supply is sometimes called a driver. It can sit in the plug adapter or inside the frame.
Duratrans
A large-format backlit color transparency film invented by Kodak and trademarked in 1982. The name is now used loosely for any backlit print film made for light boxes.
Edge-lit
The LEDs line the rim of a clear acrylic light guide panel, which carries their light inward and turns it forward through the picture. With nothing bulky behind the panel, edge-lit frames can be very slim. The Lumi Frames Lightbox and the Edge both work this way.
Float mount
A way of mounting art so it seems to hover. The piece sits raised off the backing, with its edges visible and no mat covering them. A floater frame does the same for canvases, leaving a gap between the canvas and the frame. The Lumi Frames Neon uses a floater-style profile.
Frame depth
How far a frame stands out from the wall. For a display case, interior depth is the usable space inside: roughly 2 in in the Lumi Frames Shadow Box, and roughly 3 in in the Jersey case.
G to K
Glazing
The clear front layer of a frame, made of glass or acrylic, that protects the artwork. It can be anti-glare, anti-reflective or UV-filtering.
Halo lighting
Light aimed at the wall behind a frame, so a soft ring of glow surrounds it and you never look straight into an LED. See the Lumi Frames Halo.
IR remote
An infrared remote sends commands as invisible light, so, as Wikipedia notes, it needs a line of sight to the receiver. Bluetooth app control does not.
Kelvin (K)
The unit of color temperature. ENERGY STAR’s buying guide lists 2200–3000 K as soft or warm white, 3500–4100 K as neutral or cool white and 5000–6500 K as daylight. Kelvin describes color, not brightness.
L
LED
A light-emitting diode: a semiconductor that gives off light when current flows through it. ENERGY STAR calls LEDs directional: they send light one way rather than all around, which is why they can be tucked along a frame’s edge or pointed at the wall.
LED neon
Lines of light that imitate glass neon using LEDs. Closely packed LEDs sit behind a frosted cover that blurs the individual dots into one smooth glowing line, with no glass tubes or gas. See LED neon vs glass neon and the Lumi Frames Neon.
Light box
A shallow box that lights a translucent image evenly from within, either backlit or edge-lit. Poster light boxes are sized for movie one-sheets.
Light guide panel
A clear acrylic sheet that carries light inward from LEDs at its edges. A pattern of dots or bumps, denser farther from the LEDs, sends the light forward evenly. The same idea lights many flat screens.
Lumen
The total visible light a source gives off. ENERGY STAR advises shoppers to judge brightness by lumens, not watts.
Lux
Illuminance: lumens per square meter landing on a surface. Wikipedia gives 320–500 lux as typical office lighting, and NEDCC notes that one foot-candle is about 11 lux. Conservation limits are stated in lux; see do LED lights fade art?
M to R
Mat
A paper-based border between the artwork and the frame. It keeps the artwork from touching the glazing, and acid-free board avoids the brown “mat burn” that acidic mats can cause. In a backlit frame, a thick mat stays dark while the print glows.
Multi-zone LED
An LED strip divided into sections that are controlled separately, so different parts of one strip can show different colors at the same time. That is what makes flowing multicolor light possible. See how color-changing frames work.
One-sheet
The standard US movie poster size, 27 × 40 in. Older one-sheets were 27 × 41 in. See the picture frame size guide.
PWM flicker
Pulse-width modulation dims LEDs by switching them on and off rapidly. At low frequencies the flicker can be noticeable, while above the eye’s flicker fusion threshold it cannot be seen. Our LED frame safety guide covers flashing effects.
Rabbet
The recess along the back inner edge of a frame that holds the glazing, artwork and backing. It is called a rebate in British English. Its depth limits how thick a stack the frame can hold.
Rated life
How long an LED is expected to last. ENERGY STAR explains that an LED’s “lifetime” is a prediction of when its light output will have dropped by 30 percent, not the point at which it goes dark. Treat any hours figure on a spec sheet as the manufacturer’s claim.
S to W
Shadow box
A deep display case with a glass or acrylic front, made for three-dimensional objects such as medals, tickets and keepsakes. Lit versions hide LEDs around the inner edge.
Standoff
A small metal post that passes through holes in the corners of a panel, such as an acrylic print or sign, and holds it clear of the wall with a shadow gap behind. See how to light up acrylic art.
TM-30
A method from the Illuminating Engineering Society for rating color rendition. The U.S. Department of Energy explains that it scores fidelity (Rf, 0 to 100) using 99 color samples, compared with 8 for CRI, and adds a gamut index (Rg) in which 100 means no average change in saturation.
Tunable white
LEDs with warm and cool white channels mixed to give any white in a range. The Lumi Frames Halo, for example, tunes from 2700 to 6500 K.
USB-C power
The reversible USB connector. Standard USB power is 5 V, and with USB Power Delivery a charger and device can agree on higher voltages, for up to 240 W. The Halo and Shadow Box run on 5 V USB-C.
UV-filtering glazing
Glass or acrylic that blocks most ultraviolet light. NEDCC recommends UV-blocking glass or Plexiglas for light-sensitive items and notes that LEDs do not emit UV, so the filter mainly guards against daylight.
Voltage (5 V and 12 V)
Electrical pressure. Wikipedia notes that LED strips most commonly run on 12 or 24 V DC, and USB strips on 5 V. An adapter converts your wall outlet’s voltage to this lower level. The Lumi Frames Lightbox and Jersey use 12 V adapters, and the Neon runs on a 24 V system.
Wattage
The power a frame draws. It sets the energy use and running cost, not the brightness. Energy in kilowatt-hours is watts × hours ÷ 1000; try our LED energy cost calculator.
Frequently asked questions
What is the difference between lumens and lux?
Lumens measure how much light a source gives off in total. Lux measures how much of that light lands on each square meter of a surface. A frame's LEDs have a lumen output, while the light falling on the artwork, which matters for fading, is measured in lux.
Is CRI or TM-30 more useful when choosing a frame?
CRI is the number you will actually find on most spec sheets, and a high CRI is a good sign for photos and art. TM-30 gives a fuller picture, including whether colors appear more or less vivid than under a reference light, but it appears mainly in professional lighting data.
Does a higher Kelvin number mean a brighter light?
No. Kelvin describes the color of white light, from warm and yellowish at low numbers to cool and bluish at high numbers. Brightness is measured in lumens. See the best color temperature for art for how to choose.
What is the difference between edge-lit and backlit?
In a backlit frame the LEDs sit behind the artwork and shine through it. In an edge-lit frame they run around the rim of a clear light guide panel, which turns their light forward through the picture. Edge-lit frames can be much slimmer. Our edge-lit vs backlit comparison covers the trade-offs.
Sources and further reading
- Learn About LED Lighting — ENERGY STAR (U.S. EPA)
- LED Bulbs Made Easy (Light Bulb Purchasing Guide) — ENERGY STAR (U.S. EPA)
- Protection from Light Damage (Preservation Leaflet 2.4) — Northeast Document Conservation Center
- Understanding and Applying TM-30-15 (text version) — U.S. Department of Energy
- Color rendering index — Wikipedia
- Poly(methyl methacrylate) — Wikipedia
- Backlight — Wikipedia
- LED strip light — Wikipedia
- Lux — Wikipedia
- Pulse-width modulation — Wikipedia
- Rabbet — Wikipedia
- Mat (picture framing) — Wikipedia
- Duratrans — Wikipedia
- Film poster — Wikipedia
- USB-C — Wikipedia
- Remote control — Wikipedia
How we write guides: Lumi Frames Studio researches each topic using the sources listed above and our own product specifications. We use AI tools to help draft and fact-check, and factual claims are checked against the cited sources. Spotted an error? Tell us.