Every light meter has a sensor to measure the amount and quality of light that is hitting on a surface. If measuring light from a relatively small but strong light source (i.e. a very powerful LED light) the sensor cannot absorb all of the light emitted. You may have noticed that all handheld light meters use a white plastic bulb that covers the sensor. This is called a diffuser. It is nothing more than a thin, almost transparent, plastic cap. Placing a diffuser in front of the sensor will spread the light evenly and allows the sensor to measure more accurately.
How to build your own diffuser when using Korona
Korona uses your smartphone's front camera to measure light. The camera is way more elaborate (and more expensive) than the light sensors built into handheld light meters and it allows Korona to measure more accurately then a standard light meter. Nevertheless, the light hitting the camera does not get diffused at all. This is not a bad thing for most cases, but it might lead to some clearly incorrect readings in others. In such cases, you can use a strip of regular, multi-purpose matte white printer paper in 20 lbs / 80 g/m² thickness and place it in front of your camera. This will diffuse the light and thus give you an accurate reading.
When not to use a diffuser
It is not always necessary to use a diffuser. When measuring sunlight for example, our atmosphere already does a great job in diffusing the sun's light. In such scenarios, the diffuser will only reduce a fraction of the light hitting the sensor. This gives Korona a competitive advantage against handheld light meters since you can add and remove the diffuser whenever needed.
So, say goodbye to your cheap handheld meter and measure more accurately with Korona.