SETTING STROBE AND AMBIENT LIGHTS IN OUTDOOR PHOTOSHOOT

How to work with strobe and ambient light in outdoor shoot

July 25, 2016   1765 views

BASIC PICTURE

basic aperture and shutter speed in outdoor shoot with strobe light

Let's start with the fact that in every outdoor shoot we have two objects: the model and the background. And this article is dedicated to this question: if we have just single strobe lighting unit and want to light the model with it how can we correctly expose strobe and continuous lights?

The basic thing we should understand is we will have strobe light over the model and continuous light over the background: totally different types of light. As you remember from my articles the first type could be correctly exposed with only the aperture adjustment, the second type - with both aperture and shutter speed.

Yes, the exposure of external strobe unit is limited by aperture. The shutter speed is always 1/200 sec (if we use 35mm cameras, not medium format). If we make it shorter we will lose some part of the picture with black line, if we make it longer we will just add some portion of ambient light into the picture but the exposure of the strobe light will be the same. This very short explanation will let us understand: we should use totally different principles of working with every type of light.

Now let me describe my outdoor scene. A pair of models stand in front of my camera and I put one 500 Watt/sec strobe lighting unit on the c-stand with the boom (and with sandbags, of course, too) in front of them (it stands out of the frame). This pair of model has the sun behind their backs. And it is very good condition because if we use additional light in outdoor shoot as a key light we have to reduce amount of ambient continues light over the model. The most simple ways are either put the models into the shadow or turn them with their backs to the sun.

So let’s make the first picture without any strobe lighting. (I added a pair of two continuous lighting unit on the both sides of the models facing to the camera as a prop and they don’t light the models.)

setting of aperture and shutter speed in outdoor shoot with strobe light

Camera data: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/100 sec, F-Stop: f/11, ISO: 50

I used these settings of the camera to expose correctly the background behind the models. I didn't think about models. I would light them with strobe light later. You see that they look like the black silhouettes, the best situation I could imagine.
Let’s look at these settings.
ISO - 50, the less amount I had in my camera. The sun bright and I didn’t want to close aperture too much.
Shutter speed - 1/100 - I always use this amount as a basic shutter speed. Maybe later I could feel I need to make background a little darker without changing all setting. I will short the shutter speed to 1/200 sec and make the background darker for one stop. Barely I need to do it more than for one stop.
And aperture - f11.0 - the amount to correctly expose the background.

Now Let's discuss the lighting modifier. Such aperture (you understand that f11 with ISO50 means f16 with ISO 100) is very closed and not every lighting modifier could handle with full body lighting for two models. For this we should keep the lighting unit at the minimum 5-6 feet (1.5-2 meters) distance from the models. We have no wide choice for getting this power with 500 Watt/sec strobe lighting unit: standard reflector or beauty dish. Softbox and umbrella would barely cope with this work. Maximum aperture we could get with softbox or umbrella will be f8-11 (with ISO 100). You know such big losses of light happen when we use these lighting modifiers. So I choose a beauty dish, this modifier could squeeze f22 (with ISO 100) on maximum, 500 Watt/sec power.

Ok, so I put the beauty dish over the strobe lighting unit and directed it to models. As usual to distribute the light evenly all over the models I turned the beauty dish a littler down, directed an axis of light to models’ feet. Look at the picture, this is what I got. I adjusted power of strobe lighting unit to get appropriate amount of the light over the model. The level was one stop less from maximum power.

outdoor picture without strobe light

Camera data: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/100 sec, F-Stop: f/11, ISO: 50

Now when we got nice picture let’s change amount of strobe and ambient light to understand properly how it works. Let’s play with shutter speed and aperture and look what happens. I made illustrations for that.

OPEN APERTURE

At first let’s open aperture for two stops.

open aperture in outdoor shoot with strobe light

Camera data: Camera: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/100 sec, F-Stop: f/5.6, ISO: 50

You see that the aperture affects both ambient light and strobe light.

MAKE SHUTTER SPEED LONGER

But what if I need to make background brighter (ambient light) and keep the same amount of light over the models? Right!I need to make shutter speed longer. For example for two stops: from 1/100 sec to 1/25sec. In this case we didn’t touch the aperture and the amount of strobe light is the same. Here it is:

setting of shutter speed in outdoor shoot with strobe light

Camera data: Camera: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/25 sec, F-Stop: f/11, ISO: 50

CLOSE APERTURE

But now let’s close aperture. Right! It affects again both ambient and strobe light.

close aperture in outdoor shoot with strobe light

Camera data: Camera: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/100 sec, F-Stop: f/22, ISO: 50

MAKE SHUTTER SPEED SHORTER

But what if we want to make the background darker? The simple solution doesn’t work because we can use shutter speed shorter than 1/200. Look at the picture. Shatter speed here is set to 1/500 and you see that some part of the picture just is not exposed. That always happens when you try to use the shutter speed shorter than 1/200 with strobe light.

shutter speed shorter than 1/200 in outdoor shoot with strobe light

Camera data: Camera: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/500 sec, F-Stop: f/11, ISO: 50

Here it is. But what to do?

MAKE BACKGROUND DARKER

What if we need to make the background darker for two stops. There are only one solution. To make the shutter speed shorter (we can do it just only for one stop - form 1/100 to 1/200 sec). And then to close aperture for one stop. (You remember we need to make background darker for 2 stops.
The first step will not affect strobe light. But the second one will have an effect to both strobe and continuous light (models and background). So to return brightness of models to basic level we should compensate it with increasing of power of strobe light for one stop. To maximum power of the strobe unit. That is it.

make background darker by setting of aperture and shutter speed in outdoor shoot with strobe light

Camera data: Camera: Canon EOS 5D, Focal Length: 28 mm, Shutter speed: 1/200 sec, F-Stop: f/16, ISO: 50

I hope this article will help you to understand outdoor lighting with strobe unit. Make these exercises and you will understand it properly.
Good Luck!