I installed udev 078-1 from testing, and removed hotplug, as required. Previously, gphoto2 required the following hotplug script, /etc/hotplug/usb/usbcam:

<snip>
GROUP=users

if [ "${ACTION}" = "add" ] && [ -f "${DEVICE}" ]
then
chmod o-rwx "${DEVICE}"
chgrp "${GROUP}" "${DEVICE}"
chmod g+rw "${DEVICE}"
fi
</snip>

to permit non-root operation. The result of this script could be seen in /proc/bus/usb, for example:

/proc/bus/usb/001:
total 0
-rw-r--r-- 1 root root 43 2005-12-19 14:05 001
-rw-r--r-- 1 root root 43 2005-12-19 14:11 003
-rw-r--r-- 1 root root 57 2005-12-19 14:12 004
-rw-r--r-- 1 root users 57 2005-12-19 18:24 012

Without hotplug, the usbcam script is not run, ownership of all usb devices remains root:root, and user operation is no longer possible.

I tried adding a local udev rule to change ownership of the relevant device to root:users, e.g.

/dev/u*
cr--r--r-- 1 root root 1, 9 2005-12-18 11:01 /dev/urandom
crw-rw---- 1 root root 189, 0 2005-12-19 14:05 /dev/usbdev1.1
crw-rw---- 1 root users 189, 11 2005-12-19 18:24 /dev/usbdev1.12
crw-rw---- 1 root root 189, 2 2005-12-19 14:11 /dev/usbdev1.3
crw-rw---- 1 root root 189, 3 2005-12-19 14:12 /dev/usbdev1.4

but it made no difference.

TIA.