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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 20 Jul 2012 (Friday) 13:45
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light meter use with flash ourdoors and underexpoosed background

 
brit84
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Jul 20, 2012 13:45 |  #1

Hello,
Ive recently got a sekonic 358 and want to use it to get more consistent results in my photos.

When I do people shoots outdoors I generally underexpose the background by a stop or so and use the flash to expose my subjects normally.

What I would like to do is use the meter so that I dont have to chimp as much trying to get the flash to the right power level. If I am underexposing for the background how would I set up the meter to expose the subject properly?

Thanks for your help!


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JakAHearts
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Jul 20, 2012 13:48 |  #2

This should be easy. Set the background to the exposure level you want, turn on the flash, meter the light falling on the subject and adjust power accordingly. Your meter can give you the ratio of flash to ambient if required.


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SkipD
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Jul 20, 2012 16:18 |  #3

brit84 wrote in post #14745415 (external link)
Hello,
Ive recently got a sekonic 358 and want to use it to get more consistent results in my photos.

When I do people shoots outdoors I generally underexpose the background by a stop or so and use the flash to expose my subjects normally.

What I would like to do is use the meter so that I dont have to chimp as much trying to get the flash to the right power level. If I am underexposing for the background how would I set up the meter to expose the subject properly?

Thanks for your help!

I hope you realize that you cannot do this if the camera and flash are using ETTL for the flash exposure control. They must both be set up in manual mode.


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Wilt
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Jul 20, 2012 17:15 |  #4

You can simply read the ambient light with the L358, setting exposure to -1EV with shutter speed no faster than 1/200 for flash sync. Then turn on the ETTL flash and shoot a test shot!

If you want ambient brighter or darker than the test shot, adjust aperture on lens. If you want flash brighter or darker, use FEC.

ETTL makes it so simple compared to what we used to have to do!


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Curtis ­ N
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Jul 20, 2012 17:52 |  #5

Wilt wrote in post #14746325 (external link)
You can simply read the ambient light with the L358, setting exposure to -1EV with shutter speed no faster than 1/200 for flash sync. Then turn on the ETTL flash and shoot a test shot!

If you want ambient brighter or darker than the test shot, adjust aperture on lens. If you want flash brighter or darker, use FEC.

ETTL makes it so simple compared to what we used to have to do!

Two potential problems with this approach:
1) The meter might read the E-TTL pre-flash, rather than the "real" flash.
3) E-TTL is inherently inconsistent, which is why we use flash meters to begin with.

I like Skip's approach better. Adjust the flash power manually. The meter will give you a flash/ambient ratio, and you'll soon learn what ratio creates the look you're going for.


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Wilt
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Jul 20, 2012 18:04 |  #6

Curtis N wrote in post #14746467 (external link)
Two potential problems with this approach:
1) The meter might read the E-TTL pre-flash, rather than the "real" flash.
3) E-TTL is inherently inconsistent, which is why we use flash meters to begin with.

I like Skip's approach better. Adjust the flash power manually. The meter will give you a flash/ambient ratio, and you'll soon learn what ratio creates the look you're going for.

But, Curtis, my technique involves reading ambient light only, as the flash is turned OFF, and setting the camera to underexpose.
THEN, my instructions stated to turn ON the ETTL flash and take the first test shot. So #1 does not apply in that case.

I understand your point about the relative inconsistency of ETTL flash output, and the benefit of manual flash output (and using a flashmeter to help set that). OTOH, that method is not as K-I-S-S as simply letting ETTL determine the flash output.


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brit84
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Jul 20, 2012 20:26 |  #7

SkipD wrote in post #14746091 (external link)
I hope you realize that you cannot do this if the camera and flash are using ETTL for the flash exposure control. They must both be set up in manual mode.

I only use manual, flash is off camera generally although I have used it in ettl mode on camera once or twice and agree it is hit or miss.


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brit84
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Jul 20, 2012 20:39 |  #8

Curtis N wrote in post #14746467 (external link)
and you'll soon learn what ratio creates the look you're going for.

So take a reading of ambient then flash. How to i find the average of the two? just use mode to switch between the ambiant and flash settings?


Thanks!


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Jul 20, 2012 21:02 |  #9

brit84 wrote in post #14747093 (external link)
So take a reading of ambient then flash. How to i find the average of the two? just use mode to switch between the ambiant and flash settings?

Thanks!

You do not need an 'average' reading at all. You take two readings (when the flash is not in ETTL, where it can fool the meter with its preflash)


  1. You are reading the ambient by itself, to determine the combination of f/stop and shutter speed which deliberately underexposes by -1EV. That is ONE PART of the frame (the background).
  2. The OTHER PART of the frame (your subject) will read the combination of manual flash output + ambient

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brit84
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Jul 20, 2012 21:21 |  #10

Wilt wrote in post #14747151 (external link)
You do not need an 'average' reading at all. You take two readings (when the flash is not in ETTL, where it can fool the meter with its preflash)

  1. You are reading the ambient by itself, to determine the combination of f/stop and shutter speed which deliberately underexposes by -1EV. That is ONE PART of the frame (the background).
  2. The OTHER PART of the frame (your subject) will read the combination of manual flash output + ambient

Ohoook! think I'm getting it now.

So if my ambient reading is 200 and f4 (assuming this is my underexposed settings) and my flash gave me a reading of f5.6 then I would be good. If it came up as f9 I reduce flash power and so on.

right?;)

thanks again!


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Jul 21, 2012 10:36 |  #11

brit84 wrote in post #14747230 (external link)
Ohoook! think I'm getting it now.

So if my ambient reading is 200 and f4 (assuming this is my underexposed settings) and my flash gave me a reading of f5.6 then I would be good. If it came up as f9 I reduce flash power and so on.

right?;)

thanks again!

Right understanding. This reflects what we often tell folks to do when thinking about flash shots using ambient light, too...a single photo is really two in one: the flash illuminated portion, and the ambient illuminated portion.


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Jul 21, 2012 11:33 |  #12

Indeed, youre getting it! Remember to set your camera ISO and meter ISO the same. Otherwise, youll be chasing your tail all over and thinking "What the F-stop?" :D


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brit84
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Jul 21, 2012 12:20 |  #13

Great!
Thanks for your help again. Bringing the meter into use will really help cut down time needed to get the right shot! I was just having mind failure on using between the two lighting situations.


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light meter use with flash ourdoors and underexpoosed background
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