Which Parts of My Sign Light Up? Minimum Letter Heights Explained
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The design preview shows your whole logo glowing. The finished sign lights up half of it. When that happens, it's almost always because nobody explained beforehand which parts of the sign light up and which are printed or unlit. We spell it out in every quote. This guide explains the rule behind it, sign type by sign type, and why the minimum letter height of your smallest detail decides the outcome.
In short
What lights up depends on the construction and the size. On LED neon, everything that can be bent as a neon line glows; fine text and small details are UV-printed onto the acrylic. On illuminated letters, the face, the halo or both light up, and very fine sub-lines become flat cut letters or print. A larger format brings more of the design into light.
Why not every detail can light up
Light needs room. LED neon flex has a fixed width and only bends to a certain radius. A built-up letter needs space inside for its LED modules so the face glows evenly. Make the letter too small or the stroke too thin and the light source simply doesn't fit any more.
That comes down to physics. A strapline 3 cm tall under a large logo can't be formed cleanly in neon flex. Force it and the letters blur into one bright smudge that nobody can read. So we build those elements differently. They stay visible; they just don't produce their own light.
Which parts light up, by sign type
Here's the quick version across all shop sign types:
| Sign type | Lights up | Doesn't light up | Lower limit |
|---|---|---|---|
| LED neon | Everything formed as a neon line: lettering, outlines, logo lines | Very fine details, small text and areas of colour (UV print on the acrylic) | Depends on font and format; we check it in the design preview |
| Face-lit letters | The whole acrylic face of each letter | Aluminium returns (unless you choose illuminated acrylic returns) | From about 15 cm letter height |
| Halo-lit letters | Only the ring of light on the wall | The face, which stays matt | Very thin lines throw little light |
| Front & halo-lit | Face and halo, colours chosen separately | Aluminium returns | From about 10 cm letter height |
| Lightbox | The entire acrylic face | Opaque dark artwork, frame and sides | Fine text isn't an issue; it sits on the face as print |
| Flat cut letters | Nothing as standard (a halo can be added) | Everything; they work through material and shadow | From about 3 cm, depending on the font |
Treat those figures as guide values. The font matters more than people expect: a bold sans-serif copes with far smaller sizes than a delicate script.
LED neon: neon line or UV print?
On an LED neon sign, every glowing line is bent from neon flex and fixed to contour-cut acrylic. Anything too small or too intricate for that is UV-printed straight onto the acrylic: the little sub-line, fine flourishes, filled areas in the logo. Those elements are in colour and easy to see in daylight, but they don't glow.
A typical case from our quotes: a barbershop logo with a big name and the word "BARBERSHOP" underneath. At just under 30 cm overall height, the name lights up and the sub-line is too fine for neon flex, so it's printed. Go up a size and the sub-line can be LED neon too.
It works the other way round as well. If a large sign is planned as the full version with maximum LED coverage, you can choose to leave individual elements without neon. They're printed anyway, so the sign still looks complete; less of it simply glows. How that affects the price is explained in how much a shop sign costs.
Illuminated letters: face, halo or both
With illuminated letters, the illumination type decides what glows. Face-lit letters shine forward across the whole acrylic face and read best from a distance. Halo-lit letters throw the light backwards onto the wall while the face stays dark. Front & halo-lit letters do both, in two colours if you like: white to the front, your brand colour behind.
Two things people underestimate with halo lighting:
- The wall is part of the sign. The halo forms on the wall, not in the letter. It looks best on light, matt walls. On very dark surfaces it barely shows, and front & halo-lit letters are the better choice.
- The gap shapes the light. Halo-lit letters need 2–3 cm off the wall for an even, soft ring of light; dual-lit letters about 2–4 cm. The bigger the gap, the softer and wider the halo.
And the strapline? Very fine text can't sensibly be built as an illuminated letter. Small extra lines such as "Est. 1998" or opening hours become flat cut letters or print. For very small lettering under 10 cm, LED neon is often a better answer than a halo-lit letter.
Lightboxes: light colours glow, dark stays dark
On a lightbox the whole face glows evenly, and your logo and text sit on it as print or vinyl. There's no minimum height for the light here, but there's a different rule: light, translucent colours glow with the face, while opaque dark areas look dark at night.
So a black logo on a white face becomes, after dark, a glowing white panel with a black silhouette. If you want an area to look black by day and glow white at night, we use day/night film. The aluminium frame and sides don't light up. A double-sided lightbox, for example as a projecting sign, glows on both faces. Whether a lightbox or individual letters suit your frontage better is covered in lightbox vs sign tray vs built-up letters.
RGB and switching on: two common misunderstandings
RGB doesn't mean rainbow. On an RGB sign the whole sign changes to one colour at a time, never letter by letter. If you want fixed colours for different elements, plan them as single-colour neon lines in different colours.
No chasing lights. LED switches on instantly and evenly, not in sequence. The sign is fully lit the moment the power's on, with no warm-up and no flicker.
How big does the sign need to be for everything to light up?
It comes down to your smallest element, not your largest. If the sub-line is to glow in LED, it has to reach the minimum height itself, and the whole sign grows with it. For legibility there's also the rule of thumb of roughly 1 cm of letter height per metre of viewing distance. Our guide on how big your sign should be brings both together.
What we see most often: a requested size that works for the main element and is just too small for the sub-line. We then show you both routes: your size with a printed sub-line, and the smallest size at which everything lights up. You decide afterwards, without pressure.
How the design preview shows what lights up
- Send your logo or artwork with the size you have in mind and, ideally, a photo of the wall or shop front.
- Get a free digital design preview. It shows the sign at your chosen size and marks which elements light up and which are printed or unlit.
- Approve or adjust. Bigger, a different font, less LED: the sign only goes into production once you approve the preview. Production then takes about 2–3 weeks.
Fixings come with every sign, and if you don't have a fitter, we'll help you find one near you. LED neon comes with a 24-month warranty, a dimmer and remote, and a clear 2 m cable as standard.
Frequently asked questions
Is a printed sub-line invisible at night?
It doesn't produce its own light. How well you can see it after dark depends on the surrounding light. In daylight it's in full colour and easy to read.
Can flat cut letters be illuminated later?
Many flat cut letters can be upgraded to halo-lit letters later. If an unlit logo just needs to be seen at night, a well-aimed spotlight is often enough.
Can a metal logo have an illuminated face?
No, metal doesn't let light through. A halo behind the letter is possible, with the face staying pure metal. If you want a glowing face, face-lit letters are the better fit.
See what lights up before you order
Send us your logo and we'll show you in the preview exactly what lights up at your size, and what a larger format would change. Request your free design preview