I have been re-reading Wikipedia's article on Phonetic transcription. It's a huge subject, and the article does a reasonable job of covering the basics, but I have some problems with the sections “Versus orthography”, “Narrow versus broad transcription” and “Types of notational systems”. I'll be going through these one by one, so here I'll just comment on the first one.
I believe there are a couple of oversimplifications in “Versus orthography”. The statement “Other languages, such as Spanish and Italian have a more consistent (but still imperfect) relationship between orthography and pronunciation (phonemic orthography)” implies that no language has an orthography that is genuinely "phonemic", but the Wikipedia article Phonemic orthography states that “That ideal situation is rare but exists in a few languages”. There is another oversimplification in the statement “phonetic transcription can provide a function that the orthography cannot. It displays a one-to-one relationship between symbols and sounds, unlike traditional writing systems”. But phonetic transcriptions of a single utterance may identify different numbers of sounds: Lodge (2009, pp. 67-8) shows five different phonetic transcriptions of the word ‘cab’, some of which contain a symbol for the aspiration component of the initial /k/ and others a symbol for the final release of /b/. Laver (1994, p. 558) gives an illustration of successive efforts at transcription of a Czech utterance by a transcriber who was an expert in phonetics but not a speaker of Czech. Three transcriptions of the word [prɒstʃi] (“simpler”) have different numbers of symbols. This shows that the principle of one-to-one correspondence between a phonetic symbol and a single sound is not strictly true in practice: what we identify as “a sound” is often arbitrary. The other part of this claim, that orthography is not able to offer a one-to-one correspondence between letters and sounds, is shown to be incorrect by the statement quoted above from the phonemic orthography article. I hope to modify this section to take account of these points.