Read the sheet in the order it is installed
Most gobo projection light sheets list ten numbers and leave out the three that decide the result. Work from the wall backwards — image size, throw distance, ambient light — and treat everything else as supporting detail. The numbers that matter are the ones you can verify on site with a tape measure and a lux meter.
Output numbers, ranked by how much they lie
Wattage tells you the running cost, not the result. Two gobo projection light models at the same wattage can differ by 30% at the wall because of lens efficiency and LED binning. What you actually care about is contrast: the image needs to be meaningfully brighter than the surface it lands on, and that is a lux comparison, not a lumen one.
| Figure | What it measures | How much to trust it |
|---|---|---|
| Lumens | Total light leaving the lamp | Rough sorting tool — ignores lens and gobo losses |
| Lux at the wall | Light arriving on the surface | The number that matters, rarely quoted |
| Watts | Power drawn from the supply | Tells you running cost, not brightness |
Throw distance and image size
Check whether the quoted throw is to a white wall in a dark room, because that is where the number comes from. On a gobo projection light intended for a gallery, the realistic working distance is usually shorter than the maximum on the sheet, since contrast — not reach — is what fails first.
| Throw | Typical image width | Practical note |
|---|---|---|
| Short, around 5 m | 0.5 – 1.5 m | Bright and easy — most indoor work |
| Mid, around 35 m | 1.5 – 3 m | Where lens quality starts to matter |
| Long, beyond 35 m | 3 m and up | Contrast fails before reach does |
The optical spec most sheets leave out
Two numbers govern the image: gobo image area and the resolution the lens can carry. Glass gobos can be engraved far finer than any gobo projection light lens in this class will resolve, so the practical limit is optical. That is worth knowing before you pay for engraving detail nobody will see from 10 m away.
IP rating and electrical data
Ratings age. A gobo projection light that left the factory rated IP65 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.
Questions worth asking the supplier
Four questions separate a supplier who knows the product from one reading a sheet. What is the image width at my throw distance? What is the gobo image area? Is the IP65 rating for the housing alone or the whole assembly? And what is the lead time on a replacement gobo? A good supplier answers all four in one reply.
