Any first-time visitor to Brazil is struck by how racially mixed its people are. Of the country's population of 175 million, almost half are black or of mixed race - and "mixed" encompasses a huge variety. But visit university campuses and you will get quite another picture. Of the 6.8 per cent of Brazilians who enter higher education, the vast majority (83 per cent) are white.
In an attempt to reverse this, President Luiz Inacio Lula da Silva is introducing positive discrimination in the form of quotas for black (pretos) or partly black (pardos) students.
Universities are allowed to choose what criteria they set to implement such quotas. The University of Brasilia (UnB), the country's first federal university to adopt positive discrimination, has opted for what is arguably the most controversial route: photographs.
The university, explains Dione Moura, who belongs to UnB's social, ethnic and racial commission, took photos of candidates and analysed them "scientifically" according to racial characteristics, to decide if applicants qualified as "negro" (including black and mixed-race). A spokesperson for UnB says the analysis of photos is based on phenotypes, including hair, skin colour and facial features, which together form "a group of physical characteristics that identify blacks and mixed-race people in Brazil".
Of 4,385 candidates who attempted to enter through this quota system, 4,173 were accepted. The rest failed the photographic "race" test.
Maria-Tereza Moreira de Jesus, a black poet and writer, has reservations about the scheme. "Racism exists - from how one is treated in a shop to being interviewed for a job," she said. "But basing entrance on race is another form of racism."
Critics say that positive discrimination is not the answer to inequality. If black students are failing the examination for the state universities - considered the nation's best - it is because preparation in the public sector at high-school level is inadequate, not because the universities or society are racist.
But Moura says the inequality that exists in Brazil - from income levels to types of work - is mirrored by the inequality in access to education. She argues that UnB's new policy will result in an increase in the proportion of black students from 2 per cent to 20 per cent.
It is too early to tell just how successful these schemes will prove in eradicating racism. However, the quotas have made one thing clear: in a country as racially mixed as Brazil, deciding who is black is no easy feat.