How measuring Light Intensity on a cheap way?

[alessandro2011]

I found this resource:
Measuring Light Intensity with your Camera's Meter
but i don't known how much accurate and reliable is the result obtained from this system because i haven't a lux light meter.
Someone could make some test on different hours for understand if is good and/or possibly understand if there is one standard deviation, which remains unchanged during the measurements so that is possible add it to get the more correct result?

Note:
1) It isn't necessary take the shoot, it's sufficient see the histogram on the camera.
2) It isn't important the subject.

[Ray]

Alessandro,

That is going to be an approximation only, as things like the true color and reflectivity of your piece of white paper, and how close you get the shooting directly perpendicular to it will affect the resulting readings, as will the fact that most cameras have "stepped" intervals, and not a continuous stream of f-stops and shutter speeds.

However, in determining the needs of plants, they will be close enough.

[alessandro2011]

Some day ago, when was present a nice day, i make an experiment, i have simulated one shoot at one leaf of Salvia officinalis that i have on my small
terrace at 12.00 a.m. on full sun, based on the histogram i have used these setup:
ISO: 100
Aperture: f/5.6
Exposure: 1/500
The result was:
Lux 10760
I have the impression that was too lower.
But i simulated that shoot, normally, don't perpendicular, i will make another attempt when the weather will be better, because i want understand how this particular affect the result.
However i have underestimate what big difference make even a single stop on the final result ...