Laughter was a serious matter at a clown convention in the Mexican capital, where hundreds of the performers gathered this week to discover some of the secrets of making people laugh.

The most important lesson at the four-day event was the difference between being a simple joker and a top-notch merry-maker.

Master clown Tomas Morales, who organized the 17th annual Feria de la Risa, or Laughter Fair, said what he calls "simple" clowns taunt their audiences searching for flaws, turning the spotlight away from themselves and onto their viewers.

What he describes as "prepared" clowns keep the focus on themselves, entertaining the audience without resorting to the ridicule of others.

Morales, who has been performing for 19 of his 60 years, plays a "grotesque" clown called Llantom and changes his color scheme daily. His fright wig always matches his suit, sometimes blue, other days electric orange, or perhaps yellow.

Demonstrating the kind of humor employed by more sophisticated clowns, Llantom delighted a young boy who held a stuffed toy monkey as he walked across a theater lobby. Llantom introduced himself to the child and told him how much he liked his dog, referring to the plush fake monkey.

Llantom says some of the more sophisticated clowns employ props, such as white-faced, rose-color costumed Paulynn, who carried a white fake dog called Chuleta. Another clown had a fake pet rat in his pocket.

Those attending the clown fair paid $50 to attend workshops teaching skills ranging from how to twist balloons into sculptures to the intricacies of clown makeup and costumes.

But the biggest attractions were afternoon performance competitions at local theaters, with clowns filling red plush seats to draw inspiration as they watched each other's skits. Participating in a theater on a well-lit stage is a real luxury for clowns who have spent the previous year working private parties or in the streets.

Several clowns posed for portraits taken with a digital tablet. Among them were an 83-year-old woman who plays a white-faced clown called Tikitiki, a group of seven teenage boys with cat-like faces known as the Amigatos, and a traditional-style French medieval court jester. A few party-crashers made up to look like famous personalities such as Charlie Chaplin or Albert Einstein made cameo appearances.

Visiting the convention on my time off as a photo editor for The Associated Press, I discovered that quality portraits can be made using a digital tablet as long as there is plenty of light.

I quickly learned that keeping a rock-steady hand is key to prevent blurring. And the tablet's wide screen means you can't be inconspicuous, so I had to work with people gathering behind me to look over my shoulder.