The semantic differences between "black but beautiful" and "black and beautiful" seem to be really important to me, and although most editions (http://biblehub.com/songs/1-5.htm) give some form of contrasting conjunction, I read recently in "Black Legacies: Race and the European Middle Ages" by Lynn Ramey that the original Hebrew is more closely translated as 'and,' and that the translation 'but' started with Jerome's Vulgate (nigra sum sed formosa). I don't know Hebrew at all, so I'm curious as to why the discrepancy? And if it was a mistranslation by Jerome, why is it maintained in so many contemporary versions?
I can't comment directly on scholarly consensus, but I can give you an overview of the translational issue.
Here's the Hebrew of 1:5, for those playing at home:
שְׁחוֹרָ֤ה אֲנִי֙ וְֽנָאוָ֔ה בְּנ֖וֹת יְרוּשָׁלִָ֑ם כְּאָהֳלֵ֣י קֵדָ֔ר כִּירִיע֖וֹת שְׁלֹמֹֽה׃
That first word (שְׁחוֹרָ֤ה), reading right to left, translates as 'black', the second word is "I", and the third word (וְֽנָאוָ֔ה ) "beautiful" with the conjunction ו is normally translated "and", but it can have a range of meanings, which I get to below.
The LXX goes with: Μέλαινά εἰμι καὶ καλή : "I am black and beautiful"
The Vulgate goes with: Nigra sum, sed formosa : "I am black, but beautiful"
Modern English translations tend to opt for contrast.
The key question is really 'what is the relationship between "black" and "beautiful" in the poetic context, is it mere conjunction, or does it imply contrast?' Most commentators understand that the reference to blackness here is not a racial descriptor, but a hyperbolic expression for 'tanned'; in the historical context (and this remains similar in numerous contexts today), a deep sun-tan is a sign of outdoor, manual labour, and so pertains to low socio-economic status and thus paleness of skin as a sign of wealth and leisure, is a concomitative feature of beauty. Given that Israelites were not historical black-skinned, this is a likely understanding, in which case understanding 'beautiful' and 'black' to be a juxtaposition is legitimate.
(Modern) English translations do not really base themselves off the LXX/Vulgate tradition, except for a few rarities. Almost all modern translations work from a Hebrew text. There are some good and important questions to be asked about blakeness, reception history, and the Bible, but in terms of a direct question of how to understand Song of Songs 1:5 in its historical setting, I don't think reading it in terms of race is accurate.