October at the Scottish National Portrait Gallery and the BP Portrait Award rolls once more into town. An award aimed at encouraging artists to focus on portraiture, it is open to anyone aged 18 and above with a First Prize of £20,000 and a discretionary additional £5,000 commission.

Perhaps the key to the mix here is the "anyone", the admirable open call to artists amateur and professional this year expanded by the Prize’s decision to receive digital submissions. With entry simplified to the production of a jpeg and an email, it was a move that hugely increased the number of international submissions received – 2,748, to be precise. The initial haul from 92 countries was whittled down to a “shortlist” of 456 paintings which were then viewed by the judges on canvas, or whatever medium the artist had chosen. The venture must have seemed colossal.

There are artists here from Spain and Israel, Scotland, America and shores far beyond. But just because the trawl has been widened does not, of course mean that the quality has deepened. The BP haul is always a rather mixed bag and this year is no exception, with somewhat rare forays into the artistically-inspired amongst the technically proficient offerings.

Amongst the more engaging offerings, and those that have something to say as portraits, are Irina Karkabi’s engaging portrait of Abu Muhammad, a Palestinian who had come to the artist’s Haifa studio to do renovation work. The twinkling eyes have it, here. Sobering, too, is David Jon Kassan’s portrait of Sam Godolfsky, his arms crossed protectively across his body, revealing the number branded into his skin at Auschwitz.

The Prize Winners are rather less interesting. The overall winner, Matan Ben Cnaan, has painted a tough but rather dull biblical allegory of the Jeptha story centred on a worldly-wise friend, his stepdaughter and their far-from-cuddly family dog. Painted in the Jezreel Valley, the picture is filled with blinding light and dark shadow, although there is something very unconvincing in the clash between figures and background.

Second prize winner Michael Gaskell’s technically impressive but unrewarding Flemish-inspired portrait of his 14 year old niece Eliza sees him coming second for the fourth time in the prize’s history whilst third prize winner Borja Buces Renard fields a portrait of his mother and his brother on a sofa. The backstory, of Sunday evenings spent discussing art, is a reassuring affirmation of the vitality of family life as it should be, but as with many of the stories elsewhere in the exhibition, it doesn’t quite translate.

And painful family circumstance and domestic decrepitude seems to be the defining feature of this year’s award. There is tenderness in parts, not least Grace O’Connor’s image of her sister washing her mother’s hair (My Mother, My Sister), and there are rare flashes of colour, such as Paul P. Smith’s portrait, Esther Sexton aged 12. But largely this is a rolling caravan of depression, of elderly faces daubed in institutionalized greys, of glum nudes and glummer faces, of couples resolutely not holding hands, of scowling kids. Wrinkles abound, an essay in super-photorealistic exactitude. Portraits of backs, and backs of heads, seem, too, to be in vogue, although neither Daniel Cove’s Back Portrait no.8 (a frustrating-sounding series, if ever there was one), of the back of a bare-footed woman standing rather too close to what one assumes to be a front door, nor Rebecca Orcutt’s What Now, of a friend lying on the floor facing away from the viewer, moved me in any way. The eyes, as they say, are the window to the soul, and there’s no soul here.

For where, to put it bluntly, is the joy in this gallery of downward-turned faces, posturing self-consciously on the border of tedium? Where are the imaginative leaps of portraiture that truly expose the subject? In their snapshot concentration on exposing ordinariness, a raw concentration on family relationships dominated by awkward otherness, loneliness or alienation, the leap to connect with the viewer frequently falls short. It is, one hates to say, very pedestrian in places, not least with its unrewarding emphasis on photorealism which is used in a highly meticulous manner by a number of the exhibitors, although rarely with any concomitant artistic reasoning.

Perhaps the issue is the obvious nods to the Old Masters made by many of the portraitists, who ape the format of past masters without necessarily finding that rare quality that makes a portrait a truly fascinating thing. Spanish artist Jordan Sokold captures the spirit in his slim, thoughtful, likeable portrait head of his friend Tenold, but it is less frequently found elsewhere.

The trouble is, amongst these frequently gloomy portraits and self-portraits of mothers and fathers and grannies and grandads, the ambition is often too narrow and insular, the desire to simply copy the exactitude of the face – or back – in front of the artist too overwhelming, and somewhere in there the truth of the portrait has been lost amongst the trees.

BP Portrait Award is at the Scottish National Portrait Gallery, Queen Street, Edinburgh, until February 28, 2016

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