Two recent street snapshots from Barcelona. The top image taken in the Raval, the lower image in the Boqueria.

Mouse-over to toggle between black-and-white and colour versions – on an iPad, tap the image quickly.

A frequent problem with street photography in Barcelona is getting good subject isolation. We are now starting the summer tourist season and the streets are packed with people. It often seems impossible to take a picture, with people continuously bumping in to you or inadvertently blocking the shot. And even when it does work the backgrounds are often chaotic and distracting.

One way to diminish the chaos is to use a shallow depth-of-field and render the images in monochrome. People here wear a lot of bright colours and in the first image this is quite distracting, even though the background is nicely blurred. Yet in the second image the reverse is true. Here, the low angle means that the background is the roof of the market, and rendering the colours helps to distinguish the subject.

So while a purist might argue that street photography should always be in black-and-white, in reality every image should be treated according to its merits and the needs of your own personal style.