Read the sheet in the order it is installed
Nothing on a spec sheet is dishonest; plenty of it is irrelevant. A store logo projection light sheet will quote lumen output, power draw and beam angle, but what you need is image width at your throw distance and contrast against the light already on the surface. Those require two more numbers the sheet usually does not give you, which is why they are worth asking for.
Lumens, watts and what reaches the wall
Three output figures get mixed up constantly: lumens describe what the lamp produces, lux describes what arrives on the surface, and watts describe what you pay for. A store logo projection light drawing 25–150 W might deliver 3,000 lumens, but the lux at the wall depends entirely on how wide you spread it. The same lamp projecting a 1 m image is nine times brighter than the same lamp projecting a 3 m image.
Throw distance and image size
Throw distance without image width is meaningless, and plenty of sheets quote only one. A store logo projection light that throws 18 m might give you a 1 m logo at that distance or a 6 m one, depending on the lens — a difference that decides whether the install works. Always ask for the pair: distance and the resulting image size.
The optical spec most sheets leave out
The spec most sheets omit is the maximum artwork resolution the optics can resolve. A store logo projection light with a good lens will render fine detail that a cheaper unit turns to mush, which means the limiting factor is often the projector, not the gobo. If your design has thin strokes, ask what line width the system holds at your throw distance.
IP rating and electrical data
Ratings age. A store logo projection light that left the factory rated IP44 can lose that rating the first time somebody opens it to change a gobo and reseats the gasket badly. Look for a design where routine access does not mean breaking the environmental seal, or accept that the rating applies to the unit as delivered, not as maintained.
What a good supplier answers without hesitating
Ask for measured figures rather than calculated ones: image lux at a stated distance, image width at your throw, and the gobo image area. Then ask what happens when the unit needs servicing — whether the store logo projection light can be opened on site without voiding the rating, and how quickly artwork can be re-cut if a branch changes its logo.
