Window Gobos Explained: Projecting Logos Onto Glass

A window gobo is a pattern projected onto or through a pane of glass — shopfronts, restaurant fronts, office partitions, event venues. It sounds simple. In practice, window projection has one problem that ruins more installs than every other issue combined, and it is almost never mentioned in product listings.

Two directions, two completely different results

Outside-in (front projection). The projector sits outside, throwing light onto the outer face of the glass. Passers-by see the image on the glass. Simple, cheap, and works best after dark.

Inside-out (rear projection). The projector is inside the shop, throwing light at the inner face. The glass acts as a screen, and the image is visible from the street. This is what most retailers actually want, because the projector is safely indoors.

The two setups need different glass treatment and different brightness. Choosing wrong is the expensive part.

The double-image problem

Here is the issue: glass is a mirror at night and a window during the day. And at night, a projector mounted outside glaring onto glass produces two images — one on the glass surface, one reflected back toward the street. The result is a ghosted, doubled logo that looks like a mistake.

Three fixes, in order of cost:

1. Move the projector off-axis. Angling the unit 20–30° from perpendicular kills the reflection but distorts the image into a trapezoid, which requires a gobo cut for that angle — or a projector with keystone correction. Cheap, effective, and usually enough.

2. Use matte or frosted vinyl in the projection area. A properly applied diffusing film turns the glass into a rear-projection screen. This is the standard retail solution and it also prevents the "you can see the projector" problem from outside.

3. Project from inside, out. Rear projection through a diffusing film eliminates the reflection entirely. The trade-off: brightness loss, roughly 30–50% depending on film.

Brightness: the real constraint

Rear projection through glass loses far more light than projecting on a wall. Practical starting points:

Add one wattage step beyond what the wall chart suggests whenever you project through glass. Frosted film, tinted glass, and double glazing all eat light.

Daylight: be honest about the limits

No practical LED gobo projector produces a visible logo on glass in direct midday sun. This is not a product limitation you can shop your way out of — it is the physics of ambient light versus projector output.

What actually works:

• Evening and night projection, which covers most retail trading hours in winter

• Sheltered or north-facing windows where direct sun never lands

• Interior partitions, where ambient light is controllable

• Higher wattage (150W+) improves shaded conditions but never beats direct sun

For daytime branding, a vinyl decal is the right tool. Gobos own the night — plan around that rather than fighting it.

Tiered windows, tinted glass, double glazing

Three glass types cause trouble:

Tinted glass absorbs a meaningful share of projector light, and shifts the color. A warm-white projection through bronze tint reads muddy. Compensate with more wattage and test before committing to a large installation.

Double glazing creates four reflective surfaces instead of two. Reflections multiply. Rear projection with a diffusing film is strongly preferred here.

Curved or angled windows cannot take a flat vinyl film. Front projection at an angle is the practical option, accepting some distortion.

Where window gobos genuinely earn their money

• Restaurants and bars: menu, brand mark, or happy-hour message on the window after dark

• Retail: seasonal patterns (snowflakes, hearts, autumn leaves) — swap the gobo, keep the projector

• Showrooms: logo on a glass partition without drilling or decals

• Events: logos on venue glass at evening receptions

The recurring financial argument is the same as everywhere in this category: one projector, many gobos. Seasonal window graphics cost money every season; a projector is bought once.

Installation checklist

• Measure lens to glass, not floor plan distance

• Confirm inside-out or outside-in before ordering the gobo

• Check for tint, double glazing, or existing window film

• Test with a torch at night to find the reflection hotspot

• Mount so the lens avoids direct line of sight from the street if projecting indoors

• Confirm the projector is IP65+ if mounted outdoors

Frequently asked questions

Can I project onto my shop window from inside during the day? Only in shaded conditions. Direct sun will wash out any LED projector.

What film do I need for rear projection? A matte, white, rear-projection diffusing film. Ask for "rear projection film," not standard frosted vinyl — they behave differently.

Will the projection damage the window film? No. Projectors emit no UV of consequence and generate no heat at the glass.

Can one projector serve both window and interior wall? Not simultaneously — the focus and brightness are set for one distance. Two units, or one unit repositioned.

Planning a window projection?

We supply IP65/66 projectors for window installs and cut window gobos from $39. Send a photo of your window and the throw distance — we will tell you what wattage actually works. sales@gobofactory.com / WhatsApp +86 13456752363.