There is a common conception that flash and photojournalism cannot get along. After all, flash can be obtrusive, and the preparation required for softer, off-camera flash setups can be problematic for photojournalists reacting to rapidly unfolding events. Moreover, many feel there is no room for subjectivity in news reporting, and using flash creatively risks disturbing the authenticity of a scene.

Not everyone agrees with this, however. "We are always told flash and reportage do not mix," says Italian Canon Ambassador Fabio Mirulla, whose wedding photography captures matrimony in a natural, photojournalistic manner. "But we often face situations where having a good Speedlite in your kitbag can solve very difficult moments or help you produce something creative without interfering with what is happening in front of you."

Here, Fabio lists five wedding-reportage flash techniques that he believes can also apply to photojournalism and documentary photography.

In busy situations with lots of people, a photojournalist can use flash to draw attention to a single, important subject, highlighting what is important without entirely removing context.

"Very often, numerous elements dominate and disturb a scene, making it difficult to accentuate a single subject," Fabio begins. "Using a flash enables me to 'clean' an image, giving importance only to what interests me. This is a good technique at any big event, especially when you have a crowd of people but only one subject, for example at a concert, a theatre or a conference."

By firing a flash directly at a single subject within a crowd, usually a bride or groom, Fabio isolates the subject from surrounding chaos. In situations of vibrant colour, he applies a coloured gel which contrasts with the dominant ambient tones, furthering the isolation. He prefers to position a single Canon Speedlite 600EX-RT remotely, roughly perpendicular to his subject, using a narrow zoom, around 70mm, to channel light accurately. "This allows for a three-dimensional effect, avoiding flattening the subject by using frontal flash," he says.

"The flash power must be enough to illuminate the subject and cancel out other external light," he adds. "I use manual flash, as TTL flash metering could be misled by other light sources."

Fabio deploys flash in confined spaces to highlight precise parts of a frame within a wider, and often deliberately underexposed, context. Not every photojournalist is constantly in the thick of the action, and creative techniques such as this can help add interest to everyday commissioned imagery such as portraits for interviews and other features.

"For photojournalism, you could use this technique when you have a small space and need to concentrate on only that – for example, photographing a subject in a phone box at night," says Fabio. "You could also use this wherever you have two different situations, such as rooms, in your view and you want to highlight only one."

Using flash in tight spaces concentrates a huge amount of light in a very small area, so Fabio employs a diffuser, even when the flash power is low, to soften the light and avoid blowing out highlights. "In small spaces, you don't need high flash power," he explains. "I prefer a flash zoom around 35mm to ensure a wide, even lighting.

"I use Live View to get an idea of the exposure of my background and ambient lighting," Fabio says. "I also shoot three or four test shots beforehand, to ensure I have the perfect exposure."

As well as their numerous creative applications, shadows can be useful for bringing out-of-shot elements into frame. In situations with audiences out of view, such as press conferences or interviews, this technique can enable you to tell a deeper story than a single image might otherwise allow.

Photojournalists and documentarians often cover events at night. When working against a dark sky, separating subjects from the background and creating a sense of depth can be difficult. Fabio often encounters this problem at weddings. To overcome it he uses a cross-lighting flash setup. "In these cases I place a flash behind my subjects and another in front to make them readable," he says. "If the couple decides to splash the champagne, the effect is certainly impactful." While this technique does require more of a setup than photojournalists might typically employ, keeping it in mind for when the opportunity arises could make for some truly unique shots.

For this technique Fabio controls each flash using a separate group, as each serves a different purpose. "The frontal flash is the primary light source; the back is just to outline the bride and groom against the darkness," he explains. "The flash groups are usually at different distances from the subject, meaning I need different power settings."

The frontal flash needs enough power to expose the subjects – overcoming any unpredictable lighting factors such as fireworks – but not so much as to blow out highlights or create harsh shadows. "The power is always around 1/32," says Fabio. "The back flash must be zoomed very wide, 24mm to cover the entire background. And not too much power, just enough to fill the frame. With only a little light, you can outline elements like water droplets."

"If I want to amplify the movement of the wedding party, I combine slow shutter speeds and a voluntary movement of the camera to create trails of light with still subjects," says Fabio.

The flash can be used on or off-camera to achieve this technique, but in the quickly changing situations it suits best, on-camera provides the highest degree of flexibility and freedom of movement. Fabio shoots handheld, slowing his shutter to around or below 1/10 sec.

"I choose a rather long exposure," he explains. "The flash shot freezes the subject and then, with a large movement of the camera, I look for the light sources on the scene to create trails.

"You can use this in any chaotic situation where you need to amplify movement to tell the story, for example during a riot," he continues. "If you use this technique, you emphasise strong feelings and energy. This technique enables you to render a chaotic moment in a three-dimensional way, like a movie."