Light meter

[windrider86]

I have read about how great light meters are and how easy it can make it when trying to adijust exposure on pictures however, I bought a light meter thru e-bay and have no clue what a lux is. Can anyone shed some light on the this subject as to how to properly read the meter and then adjust the camera accordingly?

[Major_Small]

http://en.wikipedia.org/wiki/Lux
^^ that has some nice examples as to how much lux certain sources of light put out.

[windrider86]

yeow ok but how to I convert that as to how I should adjust my camera modes?

[Major_Small]

you don't have a model that will just tell you that straight up?

I honestly don't have any real experience with light meters, as I use a grey card and my camera's metering system to take care of it.

[yokolok]

i am not a pro on this but here's what i know -

camera in manual mode
wb is set to flash or daylight
shutter to 1/60 or 1/125...
iso 100 or 200 depending on camera

same settings for shutter speed and iso on the light meter...

only thing you adjust is aperture after taking a reading...

what light meter do you have?

[windrider86]

Digital Lux Meter is what it says.
It came with a 4-page manual that gives you graphs on specifications, spectrum and the range and display. Ok well but then how to I know what adjustments to make to my camera for those readings is what I'm asking?

[yokolok]

i had thought it was one of those sekonic light meters etc...but apparently this is totally different...it measures the light or brightness in a certain area...i think you would have to do a lot of measurements and computations before you can arrive at the settings for photography use...

but these are merely assumptions...sorry...wish i could've helped more...

[Major_Small]

From that wikipedia page:

Specifications for camcorders (video cameras) often include a minimum illuminance level in lux at which the camera will record a satisfactory image. A camera with good low-light capability will have a lower lux rating. Still cameras do not use such a specification, since longer exposure times can generally be used to make pictures at very low illuminance levels, as opposed to the case in video cameras where a maximum exposure time is generally set by the frame rate.

While Lux aren't typically used for still cameras, it can be done. Here's how it can be used - First, measure the amount of Lux you've got, and turn that into an exposure value (EV):

Exposure Value at 100 iso

 EV     Illuminance (lx)
-4          0.156
-3          0.313
-2          0.625
-1          1.250
 0          2.500
 1          5.000
 2         10.000
 3         20.000
 4         40.000
 5         80.000
 6        160.000
 7        320.000
 8        640.000
 9       1280.000
10       2560.000
11       5120.000
12      10240.000
13      20480.000
14      40960.000
15      81920.000
16     163840.000

lx=2.5*2^EV

Once you have the EV, you can use this chart to get your aperture/shutter speed:

            a  p  e  r  t  u  r  e     v  a  l  u  e
        1.0 1.4 2.0 2.8 4.0 5.6 8.0 11  16  22  32  45  64
s    1   0   1   2   3   4   5   6   7   8   9  10  11  12
h    2   1   2   3   4   5   6   7   8   9  10  11  12  13
u    4   2   3   4   5   6   7   8   9  10  11  12  13  14
t    8   3   4   5   6   7   8   9  10  11  12  13  14  15
t   15   4   5   6   7   8   9  10  11  12  13  14  15  16
e   30   5   6   7   8   9  10  11  12  13  14  15  16  17
r   60   6   7   8   9  10  11  12  13  14  15  16  17  18
   125   7   8   9  10  11  12  13  14  15  16  17  18  19
s  250   8   9  10  11  12  13  14  15  16  17  18  19  20
p  500   9  10  11  12  13  14  15  16  17  18  19  20  21
e 1000  10  11  12  13  14  15  16  17  18  19  20  21  22
e 2000  11  12  13  14  15  16  17  18  19  20  21  22  23
d 4000  12  13  14  15  16  17  18  19  20  21  22  23  24

Or you can do that second part in your head. As you can see, an EV of 0 would be an aperture of 1.0, a shutter speed of 1 second, and an iso of 100. an increase of the EV by one means increasing the shutter speed OR aperture by one stop. As I understand it, a doubling/halving of the ISO would also have the same effect. Somebody might want to chime in here though, as I'm learning all this as I go here.