Do you remember the rather endearing home-made adverts for local restaurants and carpet shops that used to appear in cinemas? Their lack of sophistication, especially in contrast to the professional adverts that surrounded them, provoked mirth but almost certainly did not encourage a surge of customers.

Those ads have disappeared, but a similar amateurishness can be now seen in some businesses' printed and online marketing and publicity materials.

It seems so easy and cheap to take digital pictures that some companies have been tempted to dispense with the services of professional photographers altogether, instead issuing their employees with cameras.

But this can be a false economy, because an amateur, even one who can take decent snapshots, can rarely achieve the results of a trained and experienced professional.

Hundreds of pounds spent on advertising space or website design will be wasted if photographs are not top quality. An unprofessional approach can actually damage a company's image.

Advertising aside, there are many situations where it is a good idea to involve staff in taking photographs, especially if they have had some basic training.

Keith Barnes set up The Photographers' Workshop in St Clement's, Oxford, in 1982. As well as providing services for professional photographers, the company has always been involved in training non-professionals.

Its Oxford School of Photography offers a range of courses for people who have a personal interest in photography, as well as bespoke courses for companies wanting staff to use digital cameras, and/or image software such as Photoshop.

Mr Barnes explained: "Corporate clients will have different reasons for training their staff in photography. I take a careful brief to understand what it is they want to achieve and then produce a course to meet their needs."

For example, he designed a course for a major civil engineering company so its technical staff could record work in progress on building sites. The images had to be accurate and detailed, so appropriate advice could be offered when problems arose.

Another company needed its staff to take pictures of prototype products to share with colleagues working in other parts of the world, so they could give feedback on the designs.

Cost effectiveness is often an issue for small companies.

Mr Barnes said: "We produced a course for a company that was introducing a line of gift products they wanted to sell online. Because this was a start up, they wanted to take their own product photographs to keep costs low."

Once the company was successfully established, they were able to invest in professional photography. Not-for-profit organisations may face slightly different issues.

"Charities often want their volunteer workers to be able to contribute to newsletters because they cannot justify using professional photographers," said Mr Barnes.

"Some clients, who consider staff involvement important and regularly produce in-house magazines or intranet articles, may want to learn how to photograph staff in the workplace, or on staff development days."

Mr Barnes has also taught workshops where the purpose is more general team-building than a specific work-related training need.

"Instead of doing an assault course, a firm may offer a creative photography option."

Mr Barnes stressed the importance of developing people's visual awareness about what makes a strong image, as well as technical skills.

Everyone can benefit from looking carefully at pictures and learning about composition. What marks a professional, he said, is "the ability to see an image the way someone untrained will not."

Asked to share his top technical tips, Mr Barnes said: "Always use the highest resolution/file size possible.

"This may mean you can save fewer pictures on your memory card, but you can easily and cheaply buy more memory."

Many people make the mistake of thinking that images saved at low resolution for a website can also be used for printed materials, when in fact a far higher resolution is required.

He added: "Read the camera's manual - it sounds dull, but it works. And use the controls appropriate to the picture you are taking. Don't just use the fully automatic mode."

However, Mr Barnes stressed the need for companies to continue to employ professionals for some jobs..

"More enlightened clients are realising there is more to a photograph than just owning a clever camera, and that the skills of a professional photographer are worth paying for.

"How clients present themselves to the world is important and cannot be left to amateurs. Those who don't realise this will suffer."