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Archive 2012 · Using Strobes Outdoors - metering ambient
  
 
sherijohnson
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p.1 #1 · p.1 #1 · Using Strobes Outdoors - metering ambient


I had messed around with this in the past and the forum where I had gotten some assistance in determining how to meter the ambient light and then decide how to set the manual flash or strobes based on the results one would like is no longer around. Anyway, I would like to start working on this with some experimentation again. I plan to use my handheld light meter for metering the light. I have an assortment of strobes and flashes.

Any tips are appreciated.



Mar 07, 2012 at 02:04 AM
williamkazak
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p.1 #2 · p.1 #2 · Using Strobes Outdoors - metering ambient


I know others can add a whole lot more but, when shooting weddings and people outdoors, I first attempt to get an ambient reading using an incident meter, or just look at my rear screen on digital after I do some test shots, camera on M. Then, I know the background is correct for me. It is then my job to correctly light the face with a strobe on M or A. I quickly think "fill flash". A stop under for the ambient or a stop over or at the ambient, it does not matter as I am very quickly in the ballpark. I then adjust the flash to taste, keeping in mind that I really want the background where I first metered it. I can then add a key light if I want. Umbrellas can blow away in the wind. Your key light is your choice. Fill flash is my first choice outdoors.


Mar 07, 2012 at 04:59 AM
BrianO
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p.1 #3 · p.1 #3 · Using Strobes Outdoors - metering ambient


sherijohnson wrote:
...Any tips are appreciated.


The first decision is critical: will ambient be your main light, or your fill light?

Once you've analysed the direction, intensity, and specularity of the sun, you can decide how best to use the flash in that scene.



Mar 07, 2012 at 07:00 AM
sherijohnson
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p.1 #4 · p.1 #4 · Using Strobes Outdoors - metering ambient


I think more than anything in the instances I am thinking about, I want the light somewhat balanced for a natural look. I do try to avoid harsh lighting though sometimes I have seen some images that look quite amazing where I think the strobe is a touch stronger than the ambient. I know I need to play around, but I just wanted to get some ideas. I was thinking that I went with something like 1.5 stops over ambient, but like I said, all of my notes were on another forum which has gone by the wayside.


Mar 07, 2012 at 12:21 PM
sherijohnson
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p.1 #5 · p.1 #5 · Using Strobes Outdoors - metering ambient


oh, and when shooting outdoors, I normally use the sun as a backlight on my subjects


Mar 07, 2012 at 12:23 PM
Scott Clark
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p.1 #6 · p.1 #6 · Using Strobes Outdoors - metering ambient


I usually just use the camera to meter the background depending on how I want it to look, then add flash to taste depending on the look I'm going for. You can always chimp/use the histogram to make sure it's where you want before you add any other light. A lot of times I like to underexpose the background (if only a tiny bit) to give a little separation with the subject while still looking natural. Once you get your ambient exposure set, just meter the flash like you would in any other situation.
You might try experimenting with a reflector too...



Mar 07, 2012 at 02:37 PM
cgardner
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p.1 #7 · p.1 #7 · Using Strobes Outdoors - metering ambient


Outdoors backlight there are three lighting components to any ambient exposure: rim-ight (sun), key light (the dominant downward direction of the sky light modeling the face), and fill (the less intense 360 wrap-around fill effect of the skylight).

In an indoor flash shot you'd typically base exposure off the frontal key light. But outdoors in backlight the overall exposure (ISO / Aperture / Shutter) must be "pegged" to the ambient rim light. How you peg the exposure in the sunny highlights is a subjective creative decision. One can set exposure to keep the sunlit white shirt and hair under clipping to retain detail, or choose to blow it for a "hot" look. I prefer retaining detail.

The sun on a clear day is very predictably "Sunny 16" so it's not difficult to set the rim light exposure without a hand-help meter. If using conventional flash your shutter will be limited by x-sync so start by setting ISO to 100 and your shutter speed there (e.g. 1/250th) and your aperture at the predicted "Sunny 16" equivalent (e.g. f/11) and take an ambient only baseline shot then look at it with the camera clipping warning on. If using speedlights with HHS set the aperture you want to work at for DOF then adjust the shutter according to the Sunny 16 rule:

f/16 @ 1/125th
f/11 @ 1/250th
f/8 @ 1/500th
f/5.6 @ 1/1000th
f/4 @ 1/2000th
f/2.8 @ 1/4000th
f/2.0 @ 1/800th

Take a shot, ambient only and look at it with the clipping warning on. Adjust from that sunny 16 baseline until you see no clipping in the sunlit highlights on white fabric. If the subject isn't wearing anything white then adjust so the skin is at least 1/3 stop below clipping. In other works adjust until you see clipping in the sunlit skin or hair, then back down 1/3 stop by adjusting aperture smaller or shutter speed faster.

The resulting ambient only shot will look similar to this one looking grossly underexposed in the shaded side...






I use a towel on a stand to set lights because it allows me to set them without the subject (usually the wife) standing round getting bored and impatient. Unlike a flat target the 3D shape of the draped towel let's me see the rim, key and fill components of both the ambient light and the flash I add SEPARATELY.

For example look at the shot above. It is underexposed in front on the towel, but the downward "key" component of the skylight is modeling it's shape over the background level of the wrap around sky "fill". That's an important concept to grasp shooting outdoors because a face is modeled the same way in natural light with the "key" light angle changing during the day as the sun tracks in the sky in an arc.

At mid-day if you put a person with their back directly to the sun the skylight will create a centered "butterfly" pattern on the face similar to this one...







So before you think about adding any flash to deal with the contrast of the sun you need to observe the natural ambient modeling on the face created by the skylight and pose the face into it just as you would indoors next to a window. Why? Because you want to take full advantage of the soft natural lighting and the angle of the natural light will tell you where you need to put your flash "key" light to duplicate it.

Some go outdoors with flash with the idea of "overpowering the sun". What I'm suggesting here is thinking in terms of avoiding a fight with the sun by keeping it off the entire front of the subject then using your flash to complement the natural modeling of the skylight that is already there but that you may not have noticed.

Try this (if you haven't already): Put a subject in backlight, forget about what the background looks like and expose for highlights on the sky lit face. When you get the highlights on the sky lit face exposed normally you''ll be able to see how the skylight is modeling the face. If you are standing on ground level with the subject their eye sockets will usually be shaded by the brow. The solution to that problem isn't adding flash it's getting the face up into the light more. If shooting portraits outdoors I always bring along a step ladder to raise the camera POV with the subject so they are looking up into the light. If shooting candids I look around and try to find a rock, bench or some other object I can use to get above the heads of the subject.

What does this have to do with flash exposure? In my experience a lot since the ambient light from the skylight is the foundational key and fill components of the facial light the flash is overlapping and will either complement or if poorly placed cancel.

The #1 mistake photographer make with flash outdoors is thinking of it as fill and putting it too low relative to the face of the subject. What happens when flash is at chin level is that it's flat, lifting everything equally. By the time enough of it is added to match the power of the sun (i.e. fighting it and winning) the flash will also cancel all the modeling that was there before flash was added.

Below in an HHS test I was using a single 580ex flash on my bracket at full 1/1 power and adjusted my distance:

















You can see how as flash power increased the modeling of the skylight disappears. This single flash shot, also taken with the bracket better shows the cause and effect on a 3D head.







The flash, being centered, highlight most of what the camera sees. But the flash falls off front>back more rapidly than the skylight so while the front of the face is key lighted by both the sky and the flash back around the ears where the flash isn't as strong the detail revealed is mostly due to just the skylight.

The skylight is always the fill controlling the tone of the shadows. When your flash is level with the face what it does is add additional fill but that fill will fall off front > back creating 3D modeling. As the flash is raised vertically on a bracket or stand it starts modeling the face where it hits with highlights but not hitting other areas as much on the front of the face so you'll see more modeling of the cheeks, nose, eyes, lips, etc. In a backlit single flash shot the ideal angle for the flash is the same angle the "key" component of the skylight is modeling the face about 45.

Again this relates to exposure on the front of the face with flash. If you raise a single flash up off axis but centered on the nose it creates a butterfly pattern, the same butterfly pattern the skylight will already be putting there. So your exposure for the flash in the front needs to be based on exposing those highlights on the face so they look "normal" which is to say about 1/3 stop below clipping (at 240 in the red channel).

What is the simplest way I know to peg the face highlights 1/3 stop below clipping? Raise the power of the flash creating the highlights on the face until I see those highlights clip then back off the flash power by 1/3 stop. Simple common sense usually leads to simple common sense solutions to problems.

What if you use two flashes for key and fill in front on the face?

1) Adjust your fill power based on how light /dark you want the shadows on the face based on the plauyback.
2) Adjust your key power until skin clips the back off key power by 1/3 stop.

Let's say you think this suggestion is total BS and you swear by your meter. I'd challenge you to cover up the playback on your camera, go out and set light only via the meter and compare results.

What I realize back when I did use an incident meter for setting the lights was that my workflow was:

1) Take meter reading
2) Adjust lights
3) Take another meter reading
4) Take a test shot to see how it looked
5) Repeat...

When it occurred to me to turn on the clipping warning in step 4, I realize that when there was something black and white in my subject the playback and clipping warning was what told me the meter readings were correct. A first thought to add a while towel on a stand because I had trouble evaluating the playback. But with the towel I could use the + button to enlarge the image and see if there was still detail in the loops of the fabric in the brightest parts. That's when I realize the hand meter was redundant and it would be faster to just rely on the playback to judge exposure..

Indoors, outdoors, dark background or light the clipping warning on solid white tells me how to peg my rim, key and background exposures.







I like detail in rim-lit skin and clothing so as above I expose the rim light until I see it clip then back down 1/3 stop. Since I want the rim light to contrast with the front side "shaded" side of the white object I want it 1/3 stop below the rim lit parts so I adjust key in front until I see the front clip then reduce power by 2/3 stops. That puts the front side 1/3 stop below the rim lit part. On a white background if I want to see the effect of the rim lighting that is 1/3 stop below clipping as being brighter I need to make my background darker than the rim light. So as with the key light I will raise the background light to the point I see clipping then back it down by about 2/3 stop so as with the key light it is 1/3 stop below the rim light. Outdoors the only difference is the source of the rim light being the sun not the flash and the contribution of the skylight on the front of the subject and background.

There's no rule that rim lit detail can't be clipped and in some cases I will clip it. But for a portrait I like detail in skin, hair and clothing not nuked highlights and base all the other exposure settings of the lights around keeping the sunlit white highlights on the subject no higher that 250 eye dropper reading and skin no higher than 240 in the red channel which clips first.

There's also no rule against using the sun as key light on the front of the face, but that makes it more difficult to control the tone of the ratio of lighting on the face with the flash because the flash will overlap the sunny highlights.

What you'll realize if you think about it is that using flash outdoors to light a face in backlight is exactly the same in terms of where you need to put the light to model it in a natural flattering way. Getting natural looking results with flash indoors or out is a function of light angle. Your key flash needs to wind up about 45 above the eyes to get light in the eyes and cast shadow downward as in natural light, and when you move the key flash off axis to the side and start to notice the dark unfilled shadows one flash creates you'll need to add a second fill flash near the camera (or reflector) to lighten them if you want the shadows lighter than the skylight is making them.

Chuck



Mar 07, 2012 at 03:14 PM
sherijohnson
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p.1 #8 · p.1 #8 · Using Strobes Outdoors - metering ambient


Thanks Chuck, I was hoping you would share your input, you always provide details and are SO helpful


Mar 07, 2012 at 03:31 PM
Mike Mahoney
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p.1 #9 · p.1 #9 · Using Strobes Outdoors - metering ambient


Simple .. meter the ambient to taste first, then meter your strobe(s) to taste

Zach Gray has a method where he will start with his shutter at 1/100 and usually his ISO at 100 as well then he will adjust the aperture until he gets the desired exposure for the background. Takes about one second. Then he adjusts the strobes output to give the desired exposure at that aperture. Simple. And if he wants to then make his background brighter or darker he will ride the shutter speed. Simple.

The Sekonic L358 meter even has a reading that shows the percentage of flash in the overall exposure .. very handy when you're looking to either underexpose the background or keep things pretty even, or anywhere in between. Again, simple.

You can make this as complicated or as simple as you want .. but at the end of it all you just need to measure two different light sources and adjust their exposure.



Mar 08, 2012 at 12:41 AM
Peter Figen
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p.1 #10 · p.1 #10 · Using Strobes Outdoors - metering ambient


Mike is right on the money here. You actually don't even need a meter any more. If you have a decent correlation from how the image looks on your LCD screen, you can balance your exposures in less than a minute and never have to pull a meter out. It's really not complicated at all, but some people sure like to muck it up. The tools have changed and the way we work with them have changed as well - and all for the better. If you're outdoors, a Hoodman loupe is a great thing to have and will make balancing that much easier.


Mar 08, 2012 at 02:10 AM
 

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williamkazak
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p.1 #11 · p.1 #11 · Using Strobes Outdoors - metering ambient


sherijohnson wrote:
oh, and when shooting outdoors, I normally use the sun as a backlight on my subjects

That is my first attempt also, or to the side. Weddings and fast moving situations are harder to manipulate but we try our best.



Mar 08, 2012 at 03:34 AM
BrianO
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p.1 #12 · p.1 #12 · Using Strobes Outdoors - metering ambient


sherijohnson wrote:
I think more than anything in the instances I am thinking about, I want the light somewhat balanced for a natural look. I do try to avoid harsh lighting though sometimes I have seen some images that look quite amazing where I think the strobe is a touch stronger than the ambient. I know I need to play around, but I just wanted to get some ideas. I was thinking that I went with something like 1.5 stops over ambient, but like I said, all of my notes were on another forum which has gone by the wayside. ...oh,
...Show more

That narrows things done nicely. Here's how I do it; it might be different than the way the other person did it, but it should give you similar results:

Using the meter in incident mode with the dome (if it has one) extended, face the meter toward the sun and take a reading. Let's say for this example it's f/5.6.

Now, decide if you want the backlight to be a little brighter, a little darker, or the same as your main light. I usually go for a little lighter when the sun is acting as a backlight rather than fill.

So, in this case I'll want to expose my subject somewhere between f/4 and f/5.6. So I face the meter's dome toward my main light and take a reading, then adjust the light's power up or down until it reads f/4 (or whatever). If I only have one light, I'm done. If I have a fill light then I'll meter it, and I'd probably want it a stop or more dimmer than the main light, so f/2.8 or less.

In this situation, the sun would create a rim light or hair light that would be brighter than the hair lit by the main light.

If I wanted a different look -- one with a bit more pop to the subject, but not obviously flash lit -- I'd go the other way, and make my main light a bit brighter than the sunlit exposure. So, using f/5.6 for the ambient again, I'd set my main light somewhere between f/5.6 and f/8. For even more pop I might go as high as f/11.

In either of the above cases, I'd set my camera's aperture to whatever f-stop the main light was set for, and my shutter speed midway between sync speed and whatever minimum speed I could use (based on subject motion, camera shake, etc.). Oh, and you need to have that shutter speed dialed into the meter before you start taking readings.

By having the shutter set at the mid point, I could refine the ambient exposure a bit lighter or a bit darker as needed by adjusting the shutter speed, which would have no effect on the flash exposure.

As I say, this is only one way of doing it, but it has worked for me.



Mar 08, 2012 at 05:26 AM
sherijohnson
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p.1 #13 · p.1 #13 · Using Strobes Outdoors - metering ambient


BrianO wrote:
That narrows things done nicely. Here's how I do it; it might be different than the way the other person did it, but it should give you similar results:

Using the meter in incident mode with the dome (if it has one) extended, face the meter toward the sun and take a reading. Let's say for this example it's f/5.6.

Now, decide if you want the backlight to be a little brighter, a little darker, or the same as your main light. I usually go for a little lighter when the sun is acting as a backlight rather than fill.

So, in
...Show more

Brian, Thanks, I think this is closer to what I was looking for. Hopefully I have decent weather over the next day or two so I can get out and experiment with this again. Yesterday I focused on doing more of a studio type shoot and of course that is entirely different than shooting outdoors in the day time.



Mar 08, 2012 at 11:47 AM
Sheldon N
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p.1 #14 · p.1 #14 · Using Strobes Outdoors - metering ambient


Mike Mahoney wrote:
The Sekonic L358 meter even has a reading that shows the percentage of flash in the overall exposure .. very handy when you're looking to either underexpose the background or keep things pretty even, or anywhere in between. Again, simple.

You can make this as complicated or as simple as you want .. but at the end of it all you just need to measure two different light sources and adjust their exposure.


Agree with the endorsement for the Sekonic and using the Percentage readout to know your balance between flash and ambient.

I took this snapshot of my son last night to test a new modifier, and used the Sekonic 358. The percentage of flash to ambient was around 50% on the meter, don't remember exactly. It doesn't really look like a strobe photo, but without the flash the image was quite different.







RZ67 Pro II, 150mm f/3.5, Aptus 22, Gridded Chimera Strip



Mar 09, 2012 at 06:38 PM
BrianO
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p.1 #15 · p.1 #15 · Using Strobes Outdoors - metering ambient


Sheldon N wrote:
...I took this snapshot of my son last night to test a new modifier...RZ67 Pro II, 150mm f/3.5, Aptus 22, Gridded Chimera Strip


Very nice. Ya gotta love that medium format.



Mar 09, 2012 at 07:13 PM
sherijohnson
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p.1 #16 · p.1 #16 · Using Strobes Outdoors - metering ambient


Sheldon, thanks for sharing that image. I need to study up on the percentage thingy, that is the lightmeter I have. I see the sun is shining right now, so hoping I can talk my model into going out and doing a few pics


Mar 09, 2012 at 09:22 PM
Sheldon N
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p.1 #17 · p.1 #17 · Using Strobes Outdoors - metering ambient


Keep in mind that the reading is for the percentage of light between strobe/ambient that's actually hitting the dome. It doesn't know what light is coming from behind it, for example if you were shooting a backlit subject. The sun from behind might be 4-5 stops hotter than the ambient light.

It works in my example because he's sitting in open shade. If he had been sitting in direct sunlight then I might have needed to be at 90 or 100% strobe to match the power of the sun from behind. Then there would be much less ambient fill on his face, darker shadows, etc.



Mar 09, 2012 at 09:53 PM
sherijohnson
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p.1 #18 · p.1 #18 · Using Strobes Outdoors - metering ambient


well I was able to negotiate with my model I am VERY happy with the results I am getting with this so far. I appreciate the info shared so far, feel free to give me additional ideas regarding placement of my lights. I think I got what I was looking for so far in regard to exposure, just wish I had a more scenic place for test shots, but gotta work with what is handy for now.








Mar 09, 2012 at 11:06 PM
sherijohnson
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p.1 #19 · p.1 #19 · Using Strobes Outdoors - metering ambient


Sheldon N wrote:
Keep in mind that the reading is for the percentage of light between strobe/ambient that's actually hitting the dome. It doesn't know what light is coming from behind it, for example if you were shooting a backlit subject. The sun from behind might be 4-5 stops hotter than the ambient light.

It works in my example because he's sitting in open shade. If he had been sitting in direct sunlight then I might have needed to be at 90 or 100% strobe to match the power of the sun from behind. Then there would be much less ambient fill
...Show more

right, I would have probably figured that out if I was thinking about it. I always turn the lightmeter to meter the light in the direction it is coming from



Mar 09, 2012 at 11:41 PM
Steve Wylie
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p.1 #20 · p.1 #20 · Using Strobes Outdoors - metering ambient


So is this the look you were going for? Your flash exposure on her face is fine, and the background is quite dark. If that's what you were hoping for, then you succeeded. If you were looking for more balance, then slowing the shutter speed to let more ambient light in would bring the background up. Remember, aperture affects flash; shutter affects ambient. One good way to test this would be to start with your exposure as you have it in this image, and then successively slow your shutter speed by whatever increment your camera is set at (1/2 or 1/3 stop), and see how the background gets brighter with each adjustment. Don't change aperture, just shutter speed.

As to light placement, this looks pretty close to camera level as noted by the lack of shadow under the nose. I might elevate it a bit and take it just a little wider to the left to create a nice loop shadow under the nose.

Hope this helps.




Mar 10, 2012 at 12:53 AM
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