Module 2H: Off-camera Flash Notes

Using a flash off-camera provides significant control over lighting.
- Control over the quality of light.
- Control over the direction of light.
- Control over the lightness or darkness of backgrounds.
- Control over the quantity of light.

Moving the flash off-camera allows the use of various lighting modifiers like umbrellas and softboxes.
These modifiers transform the flash into a larger light source, resulting in softer light.

Off-camera flash enables the creation of desirable directional lighting patterns.
Additional flashes can be used for fill, hair, background, and kicker lights.

Off-camera flash allows for consistent exposures, independent of camera-to-subject distance.
The flash remains stationary on a stand, freeing the photographer to move without altering exposure settings.

Speedlights can be used off-camera with adapters, but monolights offer advantages.
Monolights are designed for light stands and often have built-in radio receivers.
Transmitters for monolights can control light output and manage multiple lights simultaneously.
Monolights generally offer more power and a wider range of lighting modifiers, making them ideal for outdoor use.

Multiple factors influence the amount of light on the subject:
- Flash power.
- Flash zoom head position.
- Flash output settings.
- Flash-to-subject distance.
- ISO value.
- Lighting modifiers.
Using an incident light meter is the most reliable method to measure flash output on the subject.
Take a test exposure with the meter at the subject's position to determine the f-stop.

Speedlights and monolights allow for reducing flash output, similar to a dimmer switch.
Adjustments can be made in one-stop, 1/3-stop, or 1/10-stop intervals.
Some speedlights use ratio values to indicate output levels:
- 1/1 = Full Power
- 1/2 power = 1 stop reduction
- 1/4 power = 2 stop reduction
- 1/8 power = 3 stop reduction
- 1/16 power = 4 stop reduction
- 1/32 power = 5 stop reduction
- 1/64 power = 6 stop reduction
- 1/128 power = 7 stop reduction
Some flashes, particularly monolights, use a numerical scale (e.g., 9 or 10 for full power) where each number decrease represents one stop less in output.
- 9 = Full Power
- 8 = -1 stop
- 7 = -2 stops
- 6 = -3 stops
- 5 = -4 stops
- 4 = -5 stops

Successfully balancing flash and ambient light is crucial for off-camera lighting.
Example: If ambient exposure is $f/8$ at $1/125$ second and the flash meter reads $f/11$ at power level 8 (on a monolight), the equivalent speedlight setting would be $1/2$ power.
Adjusting the monolight down to 7 (two stops reduction) results in a flash meter reading of $f/8$ .

Lighting can appear "flashy" when the background is brighter than the ambient light on the subject, requiring flash to balance the subject's exposure.
The goal is to match the subject's exposure to the background exposure.

An image taken with ambient light measured $f/4$ at $1/125$ second.
An image taken with an off-camera flash set one stop less than the ambient light (measured $f/2.8$ ) creates subtle directional lighting.
This technique adds highlights and shadows without making the flash noticeable.
Flash meters can assist in achieving the desired result.

The percentage readout on flash meters compares the relationship between flash and ambient light.
50% indicates equal ambient and flash contribution.
Below 50%, ambient light dominates; above 50%, flash dominates.
Adjusting flash output to 50-75% is a good range for natural-looking images.
Many monolights allow fine-tuning in $1/10$ th stop increments.