At work recently, I was discussing phone apps and the subject of apps that use internal sensors, including light meters and it got me thinking...
I've been working in the workshop on and off for approx 6 months now on various tasks and while I am very satisfied with the brightness level from the lighting that I installed, I often wondered how close I got to the approx 650lux average I was aiming for. I installed a lux meter app on my phone and compared readings on a few phones at work (using the same app) and we had terribly inconsistent readings between different brand phones. It seems that apps are really not to be trusted for accuracy. So I borrowed a professional illuminance meter from our building maintenance guy at work instead and took it home to perform some measurements.
In my workshop at night with all the lights turned on, I recorded 780 lux at the workbench (directly underneath a twin fluorescent tube fitting, at a height of approx 1.5m) which is a great result. I also recorded average of 430lux at various points around the central area of the workshop. This is still a reasonably good result, as it's still 50% brighter than the light levels at my desk at work of 290lux,
The target of 650lux versus the measured 430lux may seem like a large difference, however a light meter measures on a linear scale and the human eye perceives light on logarithmic scale. I'll skip the actual maths, but despite the lux meter reading 34% less than my target, the perceived light level by the human eye is actually only 19% less bright than I was aiming for. Even so, I've never felt like I needed it brighter (except for detailed work in an engine bay or under a car body, obviously) but it's just nice to be able to quantify my results.
I've been working in the workshop on and off for approx 6 months now on various tasks and while I am very satisfied with the brightness level from the lighting that I installed, I often wondered how close I got to the approx 650lux average I was aiming for. I installed a lux meter app on my phone and compared readings on a few phones at work (using the same app) and we had terribly inconsistent readings between different brand phones. It seems that apps are really not to be trusted for accuracy. So I borrowed a professional illuminance meter from our building maintenance guy at work instead and took it home to perform some measurements.
In my workshop at night with all the lights turned on, I recorded 780 lux at the workbench (directly underneath a twin fluorescent tube fitting, at a height of approx 1.5m) which is a great result. I also recorded average of 430lux at various points around the central area of the workshop. This is still a reasonably good result, as it's still 50% brighter than the light levels at my desk at work of 290lux,
The target of 650lux versus the measured 430lux may seem like a large difference, however a light meter measures on a linear scale and the human eye perceives light on logarithmic scale. I'll skip the actual maths, but despite the lux meter reading 34% less than my target, the perceived light level by the human eye is actually only 19% less bright than I was aiming for. Even so, I've never felt like I needed it brighter (except for detailed work in an engine bay or under a car body, obviously) but it's just nice to be able to quantify my results.
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