The Berne Convention evolved from a 19th century initiative started by Victor Hugo in France.
It's primary aim is to protect the rights of authors of creative work.
It says so in Article 1 (6): "The works mentioned in this Article shall enjoy protection in all countries of the Union. This protection shall operate for the benefit of the author and his successors in title."
Moreover these rights are exclusive to the author : Article 9 (1) Authors of literary and artistic works protected by this Convention shall have the exclusive right of authorizing the reproduction of these works, in any manner or form.

Authorship rights, as described by the Berne Convention, give approximately the same rights of reproduction as does the South African Copyright Law 1978.

In the European civil law jurisdictions, the rights of authors and the owners of copyright are one and the same and, hence, inseparable.
In the common law jurisdictions which have evolved through the adoption and application of English law, copyright ownership rights can be detached from authorship rights and treated differently.

South Africa is one country where this happens.

The Berne Convention is often referred to as an international copyright treaty. This is true only for countries where author's rights and copyright ownership rights are inseparable. In jurisdictions using common law, it is not true. This leads to the situation whereby copyright ownership issues are local to the country of origin but authorship rights (including copyright ownership) are international and accrue to the author outside the country of origin and hence are protected by the laws applicable in the country of publication. There are very few countries which do not give their authors copyright protection - even for commissioned work.

Put another way: copyright ownership in South Africa can belong to anyone in SA who can then have the freedom to exploit the rights given under the Copyright Act only within South Africa. As soon as work goes abroad, the copyright ownership becomes an author's right which then falls under the protection of the Berne Convention.

Hence work done here, for which the photographer does not own copyright, cannot be sold abroad without the photographer's permission of (and hopefully payment to)the photographer without infringing on the photographer's copyright.

The Berne Convention is quite explicit in neither recognising nor protecting the ownership of copyright in the country of origin.
It says " (2) The enjoyment and the exercise of these rights shall not be subject to any formality; such enjoyment and such exercise shall be independent of the existence of protection in the country of origin of the work. Consequently, apart from the provisions of this Convention, the extent of protection, as well as the means of redress afforded to the author to protect his rights, shall be governed exclusively by the laws of the country where protection is claimed."

Support for this argument comes from the US film industry where the end film credits often have the line : "So and So Production Company are the authors of this film for the purposes of the Berne Convention" In claiming authorship, the production company is also claiming copyright protection as part authors rights in all Berne signatory countries.