Can a classroom projector use the whiteboard as its screen?

Why does a projector look washed out on a whiteboard?

Many classroom whiteboards are glossy, and a glossy surface behaves like a weak mirror. Part of the projector's light bounces straight back instead of spreading across the room, so one patch of the picture looks much brighter than the rest. Text inside that patch, the hot spot, is hard to read from some seats.

Wikipedia's “Projection screen” article describes the effect on projection screens: screens that are “simply semi-glossy” show “a bright ‘hot spot’ in the screen”, which is “an enlarged (and greatly blurred) reflection of the projector's lens”. The article also says “Highly reflective flat screens tend to suffer from hot spots, when part of the screen seems much more bright than the rest.” A glossy whiteboard is a highly reflective flat surface, so the same thing happens on it.

Not sure whether your board is too glossy? WhatsApp a photo of the board to Neon+ on +60 12-565 2091.

Glass boards are the hardest case. Ghent, a whiteboard maker, writes in its guide to glass projector screens that hot spots “are common when projecting images on to glassboards”.

How do you tell if your whiteboard will glare?

Project a page of plain text onto the board and walk the room. If a bright patch sits on the picture and moves as you move, the board is too glossy to use as it stands. Wikipedia's article notes that on semi-specular screens “the hot spot's location varies depending on the viewer's position in the audience”, which is why the teacher at the front can miss what the back row sees.

Check from three places: the front corner seat, the middle of the room, and the back row. Small differences in brightness are normal: Wikipedia's article says “most viewers do not notice differences as large as 30% in the image luminosity” unless they look for them. A patch that hides words is the real problem.

A faint picture without a patch is a room-light problem, covered in Neon+'s guide to room light, image size and projector brightness (on neonplus.com.my).

Is a whiteboard or a painted wall better for a classroom projector?

A plain, matte, light-coloured wall usually gives a more even picture than a glossy whiteboard, because a matte surface spreads light instead of reflecting it straight back. The whiteboard's advantage is that a teacher can write over the projected image. A board sold for projection, such as Ghent's satin-finish glassboard, is designed to reduce hot spots.

Wikipedia's article explains that front projection screens “work on diffusely reflecting the light projected on to them”: a matte surface scatters the light across the room. For boards, Ghent says “With a satin finish on the glassboard, the projection image will be clear and visible while the projection can become too reflective on a normal glassboard.”

Room light matters on any surface. BenQ's education blog notes that projectors “rely on low ambient light to create contrast”, and that “the bright lights of a classroom lower the contrast on a projected image”, making it “harder to read”. Ghent likewise suggests “dimming lights for the best quality and brightness of the projection”. Blinds and lights change how faint the whole picture looks, and blinds cut window light reflecting off a glossy board; neither moves the projector's own hot spot.

Choosing between a projector and a flat panel in a bright room is covered in projector or TV for a classroom.

Where should the projector sit to cut the glare?

Move the projector, or shift the image, until the bright patch falls outside the picture or off the board, and keep the image only as large as the back row needs. A shiny surface reflects light back at the same angle it arrives, so a new projector position moves the hot spot. Check again from the back row after each move.

Wikipedia's article describes reflective screens sending light back “at an angle equal and opposite to the angle of incidence”. For boards made for projection, Ghent recommends “an ultra-short throw ceiling mounted projector” and suggests “working with an AV specialist for proper projection placement to reduce the chance of hot spots even further”. That suits a fixed installation.

A portable projector on a desk or tripod is moved by hand, so a teacher can shift it between lessons. The Neon+ V6 has a published 1.2:1 throw ratio, a 39-inch frame at 1 metre, and a tripod in the box. The distance to the wall sets the image size, explained in Neon+'s guide to what a 1.2:1 throw ratio means (on neonplus.com.my). The size the back row needs is worked out in how big a classroom projector image should be.

How should a teacher write on a projected image safely?

Writing on a projected image means stepping into the beam, so keep it brief: keep your back to the projector, never look into its light, and step out again to talk. For pointing at the picture, use a stick or pointer. That is Neon+'s practical advice; Kent County Council's classroom poster sets out its own rules below.

The poster, “Safe use of interactive whiteboards” (a Word file from KELSI, Kent County Council's resource for school professionals), is UK school guidance, not a Malaysian rule. Its points apply to any projector shining on a board:

• “Never stare directly into the projector beam.”
• “Always keep your back to the beam and avoid looking into the beam when walking away from the screen.”
• “When teaching, avoid standing in front of the projector”, and “use a stick or laser pointer to avoid the need to enter the beam.”
• “Pupils are to be adequately supervised when they are asked to point out something on the screen.”
• “Use blinds where possible to reduce reflection and glare.”

The poster says to consider these points “at the time of purchase”. In practice, where the projector sits decides how often a teacher has to step into its light.

What should a school check before projecting onto its boards?

Check each room's board finish, the window light, where the projector can sit, and how far the back row is. Run the ten-minute test in each room before buying projection screens or new boards. A board that passes needs nothing; one that fails may only need the projector moved, or the blinds closed if the whole picture is faint.

Check the room before you choose a projector. Send a photo of the board, the room's width and the back-row distance, and ask the Neon+ team where a projector should sit in that room. WhatsApp Neon+ on +60 12-565 2091 · Call +60 12-565 2091 · info@neonplus.com.my.

1. Is the board glossy, satin or matte? Try the walk-the-room test.
2. Can the windows be shaded during lessons?
3. Where can the projector stand so the hot spot falls off the picture and the teacher is rarely in the beam?
4. How far away is the back row? Epson's 4/6/8 rule divides that distance by 4, 6 or 8 to give the image height.
5. Is there a plain matte wall beside the board as a fallback?

The Neon+ showroom in Ipoh opens Monday to Friday 9am to 5pm and Saturday 9am to 1pm. Neon+ also has branches in Kota Kinabalu and Sibu; call ahead, as the published hours are for Ipoh. Sharing one projector between several rooms is covered in sharing one projector between classrooms.