Keep It Bite Size
What's the best length for a video? How long's a piece of string?
OK, that's a bit glib. My usual response to this question is actually- as short as possible and as long as necessary.
It might be that the viewing environment and audience dictates how long you can take to deliver your message- from 15 seconds on a trade show stand to 15-20 mins in a training video- but sometime you just have more information to present than will comfortably fit within the audience's attention span.
Here's where breaking your training, induction, awareness or product knowledge video into standalone sections or modules can give it more cut-through and better message retention. Whether it's delivered as video clips in a PPT presentation, on a standalone DVD, or as streaming clips on a web site your message becomes a lot more user friendly and targeted to specific audiences.
In a linear presentation such as a conference or induction session delivering the video portions of the message spread throughout the session rather than in one hit aids memory retention and is less onerous on the inductor.
It also allows you to tailor presentations to specific audiences. In a Health and Safety induction scenario it means that you can present information on just the areas relevant to that session's inductees- the guys working in the tunnel don't need to sit through (or watch the inductor shuttling through) the section on working at heights. The potential client at a new business pitch can be presented with information on just the areas of your service or product that they're most interested in or are important to them without watching a spiel on all the things they already know.
On a DVD, having a simple start-up menu allowing your audience to go straight to the sections of most interest to them- giving them a choice- suggests you have the confidence to give them control of the process and respect that they'll navigate their way to the right choice by themselves. You can always have a Play All button too.
In live presentations breaking your video support into smaller bites also allows for more dynamic light and shade in the presentation, not to mention the opportunity to have some fun with the medium. You can start straight in with a 'trailer' for the upcoming presentation, provide live summation and exposition of the information in between the video clips, leave the 'last word' to satisfied clients or customers.