# using a light meter outdoors



## photosoto (Jan 26, 2012)

I was considering buying a light meter eventually and I understand how to use the light meter to get the 'correct' exposure for flash, but how do you incorporate the ambient light as well?  For example, what if I wanted the background to be underexposed but get the 'correct' exposure for the subject?  adjust to a faster shutter speed and compensate with a larger aperture?


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## Josh66 (Jan 26, 2012)

Most light meters will tell you the ambient-to-flash ratio.

For example, it might say that with the current settings, the exposure would be 80% flash, 20% ambient.  Then you just adjust the settings to get that ratio where you want it.


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## Big Mike (Jan 26, 2012)

A hand held meter can be great for getting your exposure just right for your subject, whether it's flash or ambient light.  The key is that is measures incident light (the light falling on the subject) not reflected light (the light reflecting off of the subject).  

But many light meters can also be used to measure reflected light, good for measure the background.  But your camera has a built-in 'reflected light meter' so you could just use that for the background.

In your example, you could aim the camera at the scene/background and adjust your settings until the meter reads -1.  
Now you can use your flash meter to test your flash's output.  Dial in the ISO that is on the camera (on the meter) and adjust the flash power or distance until the reading until the meter gives you the same aperture that the camera is set to.  That should give you a properly exposed subject (from flash) and a background that is one stop underexposed.  

But yes, if you need to adjust the ambient part of the exposure, then you can use the shutter speed because it won't affect the flash exposure.


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## photosoto (Jan 26, 2012)

thanks for the great responses.... any suggestions on a light meter?  There are so many things that I want to buy for photgraphy but I think a light meter is going to be a necessity.  Getting  the right exposure shouldn't be a continual crapshoot.


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## Big Mike (Jan 26, 2012)

The most commonly recommended these days, seem to be the Sekonic meters.

The basic flash/ambient model is (I think) the L308S.  It should be enough for most people, but it lacks a few features of the next model up, the L-358...which seems to be the one that most people choose.


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## 2WheelPhoto (Jan 26, 2012)

I use a 358. I love it when using combined flash/ambient outdoors especially. Not only does it provide the value of each type light, but it shows the ratio and if one or the other changes it changes ratio values.  

When i walk into a studio with this meter, I can instantly know what the lights are doing which beats popping off shots for me.

Also, when setting up two or more lights I can easily find the difference in fstop values.

I really enjoy my light meter!


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## Rockadile (Jan 27, 2012)

Would I have to close down the aperture if 1/200 shutter speed isn't enough to underexpose the background?


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## gsgary (Jan 27, 2012)

Rockadile said:


> Would I have to close down the aperture if 1/200 shutter speed isn't enough to underexpose the background?



No because your aperture controls the flash exposure, you need more flash power


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## Rockadile (Jan 28, 2012)

gsgary said:


> Rockadile said:
> 
> 
> > Would I have to close down the aperture if 1/200 shutter speed isn't enough to underexpose the background?
> ...


Is it the same in a non flash situation? Only shutter speed affect ambient exposure? Wouldn't something like f/2.8 at 1/200 be brighter than say f/8 at 1/200?


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## gsgary (Jan 28, 2012)

Rockadile said:


> gsgary said:
> 
> 
> > Rockadile said:
> ...




When shooting flash and ambient you have to think about 2 exposures, ambient only there is 1 exposure so in your example if the ambient exposure was F4 1/200 one shot would be over exposed and one would be under exposed, here's an example wher flash and ambient are about equal


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