Copyright law restricts the legal right to copy photographs to those who have permission. Permission can only be granted by the copyright holder or their agent.

'Copy' in this context includes making prints, publishing or distributing photographs in any medium, or making copies of files and distributing them electronically. It includes plagiarism, the taking of a photograph based on another. If the copy resembles the original image closely enough to be recognisable as a copy of the original, copyright has been infringed.

Thanks to international agreements, copyright law is broadly similar in most countries of the world.

The original intention of copyright was to provide a means to ensure the public had a copious supply of 'good books' to read, and this principle has been extended to other forms of creative work such as paintings, music, designs of buildings and photographs.

The early proponents of copyright took the view that it was not sensible to rely on wealthy individuals to find the time and generosity to do creative work and donate it to the public. It limited the character, quality and quantity of work created, and there needed to be another mechanism capable of supporting the creative work of 'ordinary men'. The choice was between patronage (which we would nowadays recognise as employment) whereby the patron would acquire ownership in return for sustaining the work of the author, and copyright, which created proprietorial rights for the author so that an income could be realised from the work itself.

This principle has remained unchanged, although the world has certainly altered a great deal. Copyright is now widely perceived as a tool of monopoly and price control in the hands of large corporations, but for individual creators there remains no alternative mechanism of fair reward.

As soon as you place your work on the public web, you lose the innocence of not having to pay any heed to copyright. Your work may be used for any purpose unless you take care to control what others may do with it. There are no effective physical means to prevent anyone who can see your images from copying them, perhaps using them commercially or on sites and in ways that you personally disagree with or find abhorrent. Your copyright is the only tool you have to restrain such things.

Copyright is unfortunately deeply tedious and dull, and the temptation is to allow any use without considering the possible consequences. Some people have utilised the Creative Commons licenses to formalise their generous wish to share to an extent that they find acceptable whilst reserving rights they wish to retain. This is certainly worth considering, but be aware that Creative Commons licenses are complicated and consequently widely misunderstood even by some of the people who use them. They are also interpreted quite often as a sign of someone who is unlikely to enforce their rights, so may be safely disregarded. All told, it's simpler to use a copyright statement and require people to ask for permission.

Ultimately you have to decide whose photos they will be. They are yours by right, but unless you take care they will be taken from you by opportunists who have no interest in you, and whose only interest in your work is how much profit they can make. Any photograph that is good enough to use commercially or steal is not worthless.

Copyright is automatically conferred by making the photograph so there is nothing to do. This is the standard position in most countries of the world that are signatories to the Berne Convention.

Some countries operate copyright registries where you may additionally record your ownership of copyright with the benefit of additional legal protection. EG registration with the US Copyright Office allows much higher punitive damages to be sought from infringers.

The UK does not currently operate a registry. This may change. Registration was a key proposal of the 2007 Gowers review of intellectual property law.

Copyright expires 70 years after the death of the author. At that time the work becomes public domain and available to anyone to use without permission or payment.

However, even if a photo is sufficiently old for for the original copyright to have lapsed, agencies that have gone to the trouble of scanning old work often assert that the electronic version is a new work and that they own copyright. So the age of the photo is not a reliable indication of copyright status.

The author of a photograph automatically owns copyright unless they have created the photo in the course of their employment, in which case the employer owns copyright. In either case copyright can be assigned to someone else by agreement, but the assignment must be in writing.

'Moral rights' are certain legal rights under the 1988 Copyright Designs and Patents Act. They include

• The right to be identified as the author, eg byline credit
• The rght to object to derogatory treatment of a work (but only, curiously, where the author has been identified)
• The right not to have work falsely attributed, ie someone else's work appear with your byline
• The subject has a right to privacy in certain photographs, eg photos taken for private or domestic purposes may not be distributed, published, broadcast or exhibited to the public without consent. This includes weddings, private portraits etc.

There are very significant limitations to the rights to be identified as the author and to object to derogatory treatment of work:

• Moral rights do not apply to photos made for the purpose of reporting current events. Whilst news is clearly exempt of moral rights, almost any journalistic photography may be ineligible. This get-out clause and the following one were late additions to the legislation c/o lobbying by newspaper and magazine publishers - the very areas where these rights would be most significant.
• Moral rights do not apply to work published in newspapers or magazines
• Where they may apply, they must be asserted to do so by the author, usually by means of a statement such as 'Full moral rights are asserted by the author in accordance with the 1988 Copyright Designs and Patents Act', or even 'Byline obligatory'.
• Moral rights may be waived (in writing) but cannot be assigned to another party. Rights-grabbing clients often insist on a waiver so even the right to a byline is lost.
• There are limited legal sanctions for violating moral rights. A complainant may apply to the court for an injunction to prevent violation, but there are no penalties available for failing to print a byline. However photographers own terms of supply can stipulate penalties that are enforceable as contract conditions.

An included work is someone else's copyright material that appears in your photograph. Provided the inclusion is incidental, this does not infringe. The difficulty is deciding whether incidental or deliberate copying is involved. The courts use the question 'is the copy a substantially new work?' to decide this point.

This all means you have to be careful when photographing. Putting someone up against a background of a painting might be unwise, unless the painting truly is an incidental inclusion. Buildings and scupltures are copyright, but as public works they may be photographed, although a sculpture in a private location may not.

A further consideration is the inclusion of registered trade marks such as company logos. Again, incidental inclusion is OK, but a straightforward photo of a logo may constitute an infringement. Some companies are very aggressive, the London tube 'roundel' being a famous case in point. Many stock libraries exclude any image that includes the roundel whether incidentally or not, thanks to threats of legal action.

There are various ways in which a photograph or other artwork may 'derive' from another. The most common example is montage, where elements of multiple images are combined to make a new but 'derivative' work.

Compositing in this sort of manner is very routinely done by photographers and graphic designers. The new work will be copyright of its author, but infringement will arise if permission was not obtained for inclusion of someone else's copyright imagery. The owner of the original can then sue for damages or even claim joint copyright in the new work.

Note that you do not have to use an entire work for this to arise, even small elements cut from the whole are problematic. Nor does modifying those elements avoid problems unless they have been altered to the poiint that they are unrecognisable. If recognition is possible, it's an infringement.

Plagiarism, where a new work is based wholly or in part on someone else's copyright work, may also be a form of derivative work. Again, recognition of the original is the key factor.

There are not at present any special fair use provisions for derivative works in UK law, although legislation to permit fair use for the purpose of parody is expected, having been recommended by the 2007 Gowers Report

As the owner of copyright of your work, nobody may use your work without permission. In recent years, publishers and competition organisers very frequently embed clauses within terms and conditions that take unjustifiably extensive rights in any work that you submit to them. It is common for such clauses to assert blanket permission for any commercial use including the ability to sell on to other publishers or exploit in other media, and to waive your moral rights to a byline or to object to misuse.
Despite such T&C nearly always asserting that 'you retain copyright in your work' effectively the rights taken are as extensive as copyright itself, They just steal the economic value. Always read T&C carefully so you know exactly what you are agreeing. Also be on the alert for liability clauses that make you legally and financially responsible for actions of the publisher that are beyond your control.
The reason for rights grabs is of course that the 'grabber' wants the photograph to be their financial asset, not yours. Amateurs who don't think of their work as having monetary value should consider that it certainly does have value to the 'grabber', and they are effectively demanding a blank cheque. This is generosity they would be unlikely to bestow on a needy stranger in the street, let alone well-heeled corporates and their shareholders. Professionals should recognise that their work is the only asset they will ever own, and giving it away c/o 'rights grabs' is a fastrack to insolvency in the same way that 'Buy One Get Twenty Free' would be a dumb way to run a shop.

It is a legal framework for intellectual property, so inevitably it is a mechanism to regulate who owns what and who pays whom. Some would argue that this makes copyright law itself undesirable because it stops people sharing freely. However the implication of sharing freely is that nobody will bear the costs of creating the work except the creator. And that is exactly why copyright was oriiginally introduced, because without some means of ensuring reward, only the rich could afford to create anything and it was believed to be unhealthy to rely on the rich alone for creative works.

The situation has changed considerably since. Because of digital communications copies can be stored and circulated at near-zero cost and in vast numbers. And the explosion of interest in photography means that a huge population of photographers is busy creating and sharing. But still there are limits to what amateurs can achieve in their spare time and out of their own pockets. If we want photographers to take personal and financial risks, to cover subjects that require more depth than just weekends and holidays, then there has to be money involved, and copyright as a framework for the market seems inescapable.

Copyleft is the generic name for licensing schemes that permit some free copying, adaptation or derivative work provided the copy is also issued with an identical licence.

Note that copyleft is not in any sense the opposite of copyright, and seldom means the same as 'public domain' (where no copyright exists). Copyleft licences actually  rely on copyright for their enforceable limits on what may be done. For instance copyleft usually forbids copying for commercial purposes and without attribution. Breaking the terms of a copyleft license is no different from any other infirnging use.

Copyleft licensing is most commonly applied to software, where Free Open Source Software has proved highly successful, typically using the GNU General Public Liicense. This allows software to be freely used,  improved and distributed by users but disallows commercial exploitation or rebranding. Revenues are not derived from sales but from indirect services such as installation, training, and consultancy.

There are attempts to adapt copyleft principles to writing and artistic works such as photographs, Creative Commons licenses being the best known. The intention is to encourage sharing without necessarily relinquishing economic rights or bylines. However a major problem is that rather often neither the terms nor consequences are well understood by photographers or photo users and clients. Creative Commons licences are widely interpreted as meaning the copyright user has little interest in asserting the terms so are relatively safe to steal. This perception is reinforced by an almost total lack of case law against infrinngers.

Creative Commons and other 'share-and-share-alike' licenses are sometimes called viral licenses, because they require anyone who creates a derivative work to apply an identical license to their new work. Sharing with others is thereby perpetuated.

Your photographs are your work and they are your asset. If you work as a professional photographer they are your only asset. Copyright is your title to that asset.

Make no mistake, the reason others want your work is so that it benefits them. For non-commercial use this may be acceptable, you may choose to donate your work to support charities or other causes you approve of. But it is difficult to imagine why anyone would give away their work to commercial entities whose only real interest is using your work to make money for themselves. If you license your work for a fair fee, it benefits you as well. But if you assign copyright or give a free license, you must be one of those rare people who hand out wads of money in the street to strangers who are sometimes better off than you are. Who, by the way, would not think about supplying you with free goods and services just for a credit.

If you really have no interest in money and think charging for use of your work is somehow vulgar or distasteful, ask for it anyway and then donate to your favourite charity.

Please remember that even if you do not care about copyright, others do. If you allow free use of your work it undermines every other photographer who wants or needs to retain their rights. It sends a message to clients that photographs are valueless and photographers are gullible. The law reforms that gave authors control of their own work were hard won, and are an ongoing battle to maintain; commercial publishers would like nothing better than to be able to use photographs without payment or permission, as their constant lobbying for free use of 'orphan works' demonstrates. Moreover they commonly disregard assertions of the moral right to be identified as the author.

Another major issue is that of control of how the image may be used. If you do not restrict use, you have little practical influence on whether your work may be used in ways you consider objectionable.

Finally, also bear in mind that photographs can change in significance and value unpredictably with the passing years. What may seem of little interest today may be special and far from commonplace someday.  Whose photographs are they anyway? Yours, so keep it that way.

If you pay for admission you create a contract with the owner, and terms of admission are often used to restrict or take rights in your photos. These are often stated in small print on the ticket itself so you cannot claim you were not made aware of the terms of the contract. Motorsport and other sports venues are particularly fond of these conditions, sometimes claiming all intellectual property rights of anything you create, but they crop up at music venues and all manner of other places. They are open to legal challenge, mainly on the grounds that they are unfair and/or that the terms were not stated before payment. It's worth remembering that a copyright assignment has to be in writing. But a court would ask why you didn't immediately return the ticket and ask for a refund if the terms were unacceptable. The safest course is to boycott such venues - and report them in the forums here, so others can do likewise.