Halloween window projector: how to project ghosts, eyes and skeletons in your windows

A Halloween window projector turns an ordinary window into a screen the whole street can see. In the clip beside this article, a giant eye stares out of an apartment window over the city. There's no special screen and no laptop: a plain white sheet hangs inside the glass, a small projector sits in the living room behind it, and the picture is fitted to the window from an iPhone running EasyMapper Studio.

Here's how to set one up tonight, what to hang in the window, and how to run more than one window from a single projector.

It uses rear projection. Instead of shining light at the outside of the house, you put the projector inside and aim it at something translucent hanging in the window. The image lands on that material and shows through to the street, the same way a cinema screen glows from behind.

That has three big advantages over projecting onto the front of the house:

• The projector stays indoors. No rain, no extension leads across the lawn, nothing for anyone to walk off with.
• It works in an apartment. If you have a window that faces the street, you have a display. You don't need a garden or a wall.
• It needs far less light. A window is small and close to the projector, so a cheap, small projector is plenty.

The material decides how bright and sharp the picture looks from outside:

• A white bedsheet. Free and good enough, as the clips here show. Pull it tight so the picture has no wrinkles.
• A white roller blind. If you already have one, just pull it down. It's flat, so the image is crisp.
• A frosted shower curtain. Lets more light through than cotton, so the image is brighter on the street side.
• Rear-projection film or fabric. Made for the job and the brightest option, sold by the metre or in Halloween window kits.

Turn the room lights off behind it. Any lamp in the room lights the sheet from behind too and washes out the picture.

One thing to know: rear projection shows the picture mirrored to people outside. Text and anything that faces one way will read backwards unless you flip the image. An eye, a ghost or a skeleton looks the same either way.

1. Hang the sheet and place the projector. Put the projector on a table or shelf in the room, a couple of metres behind the window, pointing at the sheet.
2. Connect your iPhone and map the window. Connect over HDMI or AirPlay (connection guide), add a layer in EasyMapper Studio and drag its four corners onto the corners of the window frame.
3. Pick something to play and press play. Drop a video onto the layer, turn off the room lights and go outside to look.

Mapping is the step most Halloween window projectors skip. A projector on its own throws a rectangle, and unless it is perfectly square-on to the window, the picture spills over the frame, the wall and the curtains. Dragging the corners onto the frame makes the light stop exactly at the edge, so the ghost looks like it's inside the house rather than projected onto it.

Yes, as long as both windows sit inside the projector's beam. In the clips, one projector covers two separate panels. Each panel gets its own layer, mapped to its own corners, and each layer plays its own video. The space between the panels stays dark.

This is the cheapest way to make a house look busy. Two upstairs windows side by side, or a window and the glass panel next to the front door, can usually share one projector set back far enough in the room.

The best window content has a black background, so only the figure lights up and the rest of the window stays dark. Ideas that work well:

• A giant eye that blinks and looks around, filling the whole window.
• Dancing skeletons, one per window, for a party look.
• Jack-o'-lanterns that grin out at trick-or-treaters.
• A ghost drifting from one window to the next.
• A silhouette of a figure walking past, like the classic horror-film shot.

EasyMapper Studio includes Halloween loops built in, and anything in your camera roll works too. The Halloween projector videos guide covers where to find more, including free ones.

Less than you'd think. For a single window a couple of metres away, a 500 to 1,000 lumen projector is enough after dark. Look for:

• HDMI or AirPlay, so your iPhone or iPad can connect.
• A short throw, if the room is small, so the picture fills the window without the projector being far back.
• Quiet running, if it's in a room people use.

The lumens guide explains how brightness scales if you want to light bigger windows or the whole front of the house.

Do I need a laptop?

No. EasyMapper Studio maps and plays everything from an iPhone or iPad. It's free to download, and Premium ($7.99 a month or $39.99 a year, with a trial) unlocks the full feature set. The Halloween window projection app page has the short version.

Can people see it in daylight?

Barely. Window projection is a dusk-to-late effect. Start it as it gets dark and it gets stronger as the night goes on.

Can I project onto the glass itself?

Not well. Clear glass lets the light straight through. You need something in the window for the light to land on, even if it's just a sheet.

Will it work in a ground-floor window?

Yes, and it's often the most effective spot: trick-or-treaters walk right past it. Use a blind or a thicker sheet so people can't see the projector behind it.

Hang a sheet, point a projector at it and open EasyMapper Studio. Your window will be watching the street before the first trick-or-treater knocks. For the whole house, see the Halloween projection mapping guide.