Graduation season arrives with a very specific problem attached, and it isn't lighting. It's that almost every UK gown is black, most hoods are lined in one loud faculty colour, and the two of them together will fight whatever you put behind them unless you've thought about it in advance.
I get asked about this every June and again in November, so here's the version I'd give over the phone.
Dark on dark is where grad portraits go wrong
Put a black gown against a near-black canvas and the shoulders vanish. You get a floating head, a pair of hands and a shapeless mass where the tailoring should be. It can be done, with a firm separation light behind the subject holding the edge of the gown, and I've seen it done beautifully. But it's a lighting problem you've chosen to create, and on a day when you're shooting thirty people it's a problem you'll solve thirty times.
Mid grey is the answer that keeps working. Dark enough that a white shirt collar and the mortarboard don't blow into it, light enough that the gown reads as a garment with folds in it. Something like Warm Grey Staple at £170 for the 100 × 135 cm handles head and shoulders, and Dove Light at £430 gives you the full 180 × 270 cm for standing portraits. The whole grey shelf is worth a scroll, because the useful range here is narrower than people expect. Very light greys start to look like a passport booth. Charcoal takes you back to the floating-head problem.
Deep blue is the other one that earns its place, and it's my favourite for gold-trimmed gowns and academic dress with warm hood linings. A light dusty blue at £430 sits behind the subject without pulling colour into skin the way a green or a red will. If the university's own colours lean blue, this quietly does a job the client notices without knowing why.
Warm browns and rusts are the ones I'd think twice about. They're gorgeous for autumn family work and they do nothing for a black gown, which just sits on top of them like a hole cut in the frame.
Size depends on who else is in the shot
Nearly every enquiry I get about graduation is for single portraits, and for a single standing figure with a bit of air above the mortarboard, 180 × 270 cm is enough. £430, hangs off a normal stand, packs into a car.
The reason I'd still push you toward the 270 × 270 cm at £570 is that graduation is never only the graduate. Parents turn up. Grandparents turn up in numbers on the day itself. Three or four people across the frame need the extra width and you can't crop your way out of it after the fact. It's our most popular size for exactly this reason, and it isn't only graduation photographers buying it.
If mum, dad, two siblings and a proud grandmother are all getting in, 270 × 340 cm at £680 gives you room to sweep the canvas under their feet rather than showing a floor edge. The size ladder lays out every step with the prices.
Home studio, or the hall on the day
These are two different jobs and one backdrop rarely does both well.
A booked home or studio session is where canvas belongs. You've got time, the light's yours, the gown is on a hanger rather than being wrestled straight, and the texture in a painted surface gives the portrait some weight. Families order prints from those sittings, and a painted ground holds up at 20 × 16 in a way a flat colour doesn't.
Event day is a production line, and I'd be doing you a disservice pretending otherwise. Two hundred people, forty seconds each, someone's uncle in the queue asking how long. On that day you want something you can hang in ten minutes, that survives a mortarboard corner scraping it, and that costs little enough not to matter when it gets marked. Seamless paper. Ours is £89.99 for a 2.7 × 10 m roll and when the bottom metre gets ruined you cut it off and pull down more, which is a thing you can't do to something I've painted. There's a full paper kit at £273 if you want the drive brackets with it.
Buy the canvas for the sessions that pay for prints. Buy the paper for the day that pays for volume. They aren't competing for the same money.