This unusual image of Portsteward Strand may challenge the conventions of traditional documentary photography but, as Cathal McNaughton explains, sometimes the most unassuming scenes offer surprising photo opportunities

Award-winning Cathal McNaughton has more than ten years? experience covering conflicts and breaking news for national newspapers and international press agencies. He shares his best press photographs and reveals how he captures a subject in ways that others haven?t seen

I took this image at Portstewart Strand, which is a sandy beach that stretches for two miles along the coast in Portstewart, County Londonderry in Northern Ireland.

I wasn?t on an assignment but, as any photographer knows, a photo opportunity can arise at any time, morning, noon or night. My mind is switched on to making photographs as long as I?m awake.

I had gone to the beach because it was a sunny day. When I was there a couple of things struck me. One was the brilliant azure-blue sky and I could see that this would make a lovely backdrop for a picture. As I wandered down to the beach I saw a bright orange-red ice-cream van parked on the sand, and the blue sky provided the perfect backdrop.

It was a beautiful crystal-clear day and the light was very bright. Consequently, I tried to make a feature of the bold colours. For this image I wanted to capture something that was pleasing to the eye, and the power of the picture comes from the contrast between the blue and orange-red colours.

Every time I lay down on the sand to photograph the ice-cream van it drove off. I don?t know if this was because the driver didn?t want me to take the picture or if it was just a coincidence. We kept playing this cat and mouse game ? him driving up the Strand and me running after him until, thankfully, someone walked over to buy an ice cream so he had to stop. Luckily, the person was a woman pushing a bright orange-red pram. It was almost exactly the same colour as the van ? and this provided the perfect tie-in for the composition. I knew this was my chance to get the picture.

I had a few seconds to prepare myself before the woman reached the van. In my head I had already composed the picture so, once I was in position, all I had to do was wait until she was where I wanted her to be in the frame.

There are only three components in this image ? the blue sky, the orange-red ice-cream van and the woman with the pram. If I had added anything else the image might have been too overpowering and the composition too messy.

Although the image looks simple, the composition was critical. I wanted to show as much of the ice-cream van against the blue backdrop as I could, and from where I was positioned this was difficult to do. I had get down as low as possible and shoot upwards. If I had shot this from just an inch higher the composition would have been ruined because too much of the sand would have been in the composition. Ideally, I would have liked the wheels of the van to sit on the horizon, but in the end this wasn?t possible.

I used a 24-70mm lens with my Canon EOS 5D DSLR. If I had used a wider lens the horizon line would have been distorted and any straight lines curved. That would have thrown the whole composition.

I was working handheld and rarely use a tripod as it doesn?t suit my style of photography. I?ll often change my mind about how a composition should look, so for me shooting handheld is best.

The main subject is quite small in the frame in comparison to the surrounding sky. The subject doesn?t always have to be big in the frame to capture your attention as sometimes a small subject will draw your eye more than something big.

If you practise studying your surroundings you can learn to anticipate what might happen next. I try to think what the effect of the thing might be before it happens rather than reacting when something happens. If you can learn to do this it will give you a huge advantage when it comes to making decisions about composition and shutter speed, for example.

Sometimes I?m happy for my pictures to be nicely composed or to have strong, bold colours ? they don?t always have to have a narrative. Although I?ve been shooting in colour for a number of years I?m only now beginning to understand how to use it properly. While some images look effective in black & white, some scenes work better in colour. It?s a question of learning to use colour sparingly so it isn?t overpowering. If the ice cream van hadn?t been red, I probably wouldn?t have taken the picture at all. It was those two elements ? the blue sky and orange-red ice-cream van ? plus the woman walking by that made the picture.

Cathal McNaughton was talking to Gemma Padley

To take part in one of our free street photography masterclasses with Cathal, send an email with your name, address, telephone number and a couple of sentences about your photographic interests and experience to appicturedesk@ipcmedia.com

To see more of Cathal?s photography, or to book a place on one of his workshops and field trips, visit www.cathalmcnaughton.com