It's hard to penetrate the murky question of how light affects beers - and even harder to find two people in the trade who agree on it.
Light-strike happens when beer is exposed to specific wavelengths of light, which change some of the bitter hop compounds, altering the nose and flavour.
Some say it hits light beers harder than strong or dark beers, some say it affects some hops more than others, and others say it affects all beers and all hops.
Then there are those who say green glass or clear glass with UV filters give enough protection to avoid light-strike, and brewers such as InBev that extract the light-sensitive particles from hops to market beers like Brahma in clear glass.
An OLN taste test, organised by a leading UK brewer, gave striking results when a golden ale was exposed to varying degrees of sunlight.
Just two days after bottling, having been placed in a sunny spot in a clear bottle with lacquer to protect it against the light, the ale had a distinct nose of Marmite and fresh mint, known as "skunky" notes. A clear bottle without lacquer left in the sun for some days smelt of wet cardboard with Marmite and burnt notes.
A third clear bottle was left on a sunny windowsill for more than a month. The ale was cloudy, had particles floating in it, smelt like a honey beer with skunky, minty notes - and tasted of liquid honeycomb.
While brewers admit that different ≠people experience light-struck flavours in different ways and to different degrees, many are adamant that brown glass is the only way to make sure the beer tastes as good when it is drunk as it does when it is bottled.
Fuller's Bill Simmons says: "For us ≠quality is paramount. We feel that amber bottles give us the very best delivery for our product and that is exactly what we use. Everybody has a different opinion, everybody tastes things differently, but just because they don't notice it doesn't mean it's not there."
But others say light-strike is not such a serious worry and there are calls for innovation from marketers and beer buyers who think clear and green glass bottles could draw new drinkers into the premium bottled ale category.
Refresh UK chief executive Rupert Thompson points out that leading beers in the sector, such as Newcastle Brown Ale and Old Speckled Hen, are in clear glass. "I believe those are good beers, they are very popular and they have been instrumental in growing the sector, so it would be wrong if all beers went into brown bottles. But I think it is for each brewer to make their own decision," he says.
The bulk of Greene King's beers are in clear glass. Take-home director Neil Jardine says: "We firmly believe many of our beers significantly improve their appeal by being in clear glass, as consumers are able to see the colour of the liquid, which in many instances is very appealing.
"Clearly if light gets to a beer it does have an effect. But it is probably going too far to say it has a ≠negative effect, because for many beers it is a part of their flavour profile - and if consumers say they like that flavour profile it is a positive effect.
"It is a bit like wine ageing - the beer tastes different from when it was fresh, but people want it to because it improves and the ≠flavour gets rounder."
Shepherd Neame sales and ≠marketing director Graeme Craig adds: "There is an intrinsic connection between colour and taste in beer. Clear glass empowers consumers to make an informed choice and encourages people to try new beers."
"In recent years we have seen a trend towards a greater use of clear or flint glass, which is thought to look better on the shelf," says Chris Hellin, head brewer at Frederic Robinson, whose award-winning dark ale Old Tom was recently repackaged in a brown glass bottle.
"Obviously the longer a clear bottle is exposed to light, the greater the risk of oxidisation, so one development has been the use of a plastic shrinkwrap on the bottle trays, which can filter out ultraviolet light. In this way the oxidisation by light only comes into play once the tray is split and the bottles are placed on display." Other brewers put clear bottles in cardboard boxes.
Retailers' opinions on light-strike are as divided as brewers'. Some specialists will create an eye-catching display of bottles by shining spotlights on them. Others try to put clear bottles in the darkest corner of the shop to keep them fresh.
Chris Brown, of Southampton's Bitter Virtue, says: "We get a general resistance from people against buying beer in clear glass. They like nice beer, and when they get it home and it doesn't taste nice people learn quite quickly."
"We haven't had any customer complaints regarding light-struck beers, although we have had problems and withdrawn stock based on their appearance," says Booths beer buyer Dave Smith.
Many retailers say they have never had a complaint, and some have never tasted light-struck effects themselves.
Tesco's ale and cider buying manager Ian Targett comments: "It is down to the breweries and their marketing departments to make those decisions. If the brand is going for a traditional look and feel, then brown glass seems to be the way to go. However, if they are looking to capture a younger audience and give a more contemporary feel, clear glass would be the option."
But marketers should remember that different colours are not the only way of standing out on shelves. St Peter's Brewery's distinctively-shaped bottles are all in amber glass, and award-winners such as Old Tom and O'Hanlons' Thomas Hardy's Ale have characteristic looks of their own, without risking light-strike.