Howard nodded. “He was a real-estate salesman, he used it to make videos of properties he was selling.”

“Ah, that explains it,” said Bonnie. “We’re lucky he had it, because anything less powerful and we probably wouldn’t see half the details we have. You can make that pixel as large as you want, it’ll still be one unit. You’ll just have a big pixel. What neighbourhood averaging does is to smooth out the image by taking an average of the colour and brightness of individual pixels in a predefined area. There was an improvement in the clarity of the images, but the edges blurred and we actually lost some detail, which was to be expected. Median filtering is a similar computer technique, but it uses a median value instead of an average value. It’s a small difference, but a significant one. I ran through a three-by-three neighbourhood and then a five-by-five, right on up to a nine-by-nine. For the worst areas I’d like to use the technique I mentioned, pixel aggregation. You choose a pixel which has properties you can clearly identify in terms of colour or texture and then you gradually move outwards, adding to it pixels of matching qualities, until you grow a defined region. That produces clusters of matching pixels, which can then be highlighted. I’m afraid it’ll take me quite a while with the equipment I have.”

Howard continued to go through the photographs as he listened to Bonnie’s explanation, most of which went way over his head. One of the pictures showed a row of bald, naked figures. “What are these?” he asked.

“Yes, I’m quite proud of those,” she said. “You could barely see them in the original, and the camera only picked them up once, but they’re there all right. They’re what the snipers are aiming at. Four dummies. The sort used in shop window displays.”

Howard put two photographs on the bench. They showed two sedan cars and a large flatbed truck. “I didn’t see these in the video,” he said.

Bonnie nodded eagerly. “They were only there for a few seconds, when the plane was spinning. The quality isn’t good, but you can see the colour and make. They’re Chrysler Imperials, one blue, one white. The truck I’m not sure about. Could be a Dodge.”

“That’s good, really good,” said Howard. He made a mental note to ask the Sheriff’s Department about tyre tracks at the scene.

The next set of pictures showed a group of three people standing together, a middle-aged man with a paunch, a young man, and a woman. The older man was holding something in his hand. There was a magnifying glass on the bench and Howard used it to examine the object.

“It’s a walkie-talkie, I think,” said Bonnie. “I assume he used it to keep in contact with the snipers.”

“Is there any way of magnifying the photographs any further?” Howard asked.