Training: Using a Lux MeterBy John Honovich, Published on Jun 06, 2009
Getting good images at night is one of the most challenging problems in video surveillance. Making this worse is that generally you cannot trust the illumination ratings provided by manufacturers.
The best tool to solve this problem is a lux meter. Lux meters provide a quantified measurement of the amount of light available. Without a lux meter, you are simply guessing. With a lux meter, you can clearly see and compare the impacts of various lighting conditions. Here is a video overview of the benefits and use of a lux meter:
Choosing a Lux Meter
There are an enormous number of options for lux meters on the market ranging from under $50 to over $500. For video surveillance, the key consideration is that a lux meter can accurately measure under 1 lux (critical for low-light and night-time testing). The cheaper consumer models usually do not do this. Based on Carl's [link no longer available] recommendation, I selected the Extech LT300 [link no longer available] (for $140 USD) and I am happy with it.
Benefits of Using a Lux Meter
Using a lux meter lets you determine exactly how much light you need for video that is usable for you. This is almost always far higher than what a manufacturer states as their minimum illumination.
With this knowledge, it makes it much easier to plan new camera deployments. Take a lux meter to the proposed camera site and check the light reading. You will know in advance how well it will work or if you need to use a different camera or infrared illuminators.
For more in-depth analysis and demonstrations of low light performance, see our premium report on "How Well Do IP Cameras Work in Low Light?"
Lower Cost Options
In addition to the LT300, Extech has begun offering lower cost compact models. The LT10 [link no longer available] is part of their "Pocket Series", and sells for ~$60 online, less than half the cost of the LT300. However, two features are lacking compared to higher end models:
- No remote sensor: The unit is all in one, with the sensor attached to the base unit, so users cannot aim the sensor with one hand while holding the base with readout in the other.
- Claims accuracy only to 0.1 lux: By contrast, the LT300 claims accuracy down to 0.01. 0.1 is likely dark enough for many users, but not those concerned with super low light scenes.