LONDON: There is no such thing as an optimal length for a TV ad, with most video campaigns likely to benefit from a mix of ad lengths, each being used to achieve slightly different objectives.

So says Darren Poole, global brand director at Millward Brown. Writing in the current issue of Admap, the focus of which is TV strategy, he notes that the market research agency is testing "significantly fewer 30-second TV ads and many more 15-second TV ads than it was in the 1990s". More clients are also investing in longer 60-second ads.

But an analysis of more than 132,000 TV copy test results revealed that, in general terms, all ad lengths can be equally efficient at generating brand-linked memorability and delivering primary messages.

Poole cautioned, however, that one should not simply assume therefore that ad length doesn't matter and opt for cheaper 15-second slots. When communication objectives are complex, longer ads are better suited to the task. Similarly, longer ads deliver better on involvement.

A combination of the two can work better than either in isolation. "Cut-downs are a critical element of every media plan," said Poole, as he outlined how one UK food brand had aired a 30-second ad in two bursts and achieved an Awareness Index of 6, slightly above average.

The following season, a 10-second cut-down was introduced into the mix, and the Awareness Index rose to 11, almost doubling the efficiency of the campaign, while communication stayed strong.

To get results like this, added Poole, advertisers need to use the memorable elements of the original in the cut-down in an intelligent way and to think whether the structure of the full-length ad actually lent itself to being cut down.

Vines and YouTube offer extremes that advertisers also need to consider as they move towards overarching video-based media planning, rather than having separate strategies for TV and digital.

For the former's six-second format, Poole advised keeping content "simple but not simplistic" with only one explicit message. The longer options the latter allows have to be creatively engaging and integrate the brand into memorable moments.

"Ultimately, what works best for your brand depends on what you are trying to achieve," Poole concluded.

Data sourced from Admap