Rachel North just couldn't believe her eyes. "I was passing the infra-red camera over the landscape when two figures appeared on the monitor. It was so exciting."
She was carrying out a technical analysis of the Courtauld's Holy Trinity (see photo above) for her final-year research project when the infra-red beam picked out previously undetected figures of St Tobias and the Angel Raphael, revealing that the artist must have changed his mind at a late stage about where exactly to put the figures.
Tobias and Raphael were repositioned from the left to the right-hand side of Christ and their size increased.
Ms North speculates that a patron could have demanded the change as a condition of donating money in order to complete the painting.
This patron could have been the guild of doctors and spice merchants which backed the convent that is thought to have owned the Trinity.
The materials and techniques of the painting, considered to be the only major panel by Botticelli in which important parts are executed by anonymous assistants, were being analysed by Ms North using infra-red imaging, spot analysis and dozens of X-rays, in an attempt to determine its provenance as well as its attribution.
She has concluded that the cherubs at least were painted by assistants.
Ms North said: "They churned out a lot of cherubs in those days."
"I was going to do lasers," says another final-year student, Leone Ainapore, 26, "but then I heard the department was getting new equipment funded by the Getty Grant Program, a computer and an infra-red Videcom camera."
Instead of the expensive custom-designed program, such as the Metropolitan's Mosart or Vasari used by London's National Gallery, Courtauld decided to buy a mainstream software program, Adobe Photoshop 3.
Mrs Ainapore's task was to set up the equipment and establish the first published protocol for its use in capturing, processing, storing and outputting images.
"Digital image processing is a very powerful tool and there is a danger of enhancing an image to the point where you have inserted something that wasn't actually there," she warned. But this is the way forward for conservation departments. Our system is not better but offers an alternative for smaller, less well-off institution."
Also completed this year were research into the theory and practise of Italian retouching techniques which, unlike those of the UK, deliberately choose to restore losses using an obvious hatching technique, and gelled solvents for varnish removal.