As a starting point the use of any portable electronic device aboard aircraft is prohibited. There are a few exceptions such as portable voice recorders, hearing aids, pacemakers and electric shavers.
An operator may give a conditional permission for the use of a PED during non-critical parts of a flight if it determines that the device will not interfere with aircraft systems. An operator may however also decide not to allow any PEDs to be used aboard including those listed as acceptable.
So the answer to your question on whether digital cameras are allowed is; Yes, if the operator allows it and it is a non-critical phase of flight. Otherwise the answer is no.