Selkii wrote:
I agree with putting camera back to factory settings, but just an idea...My husband had a similar problem with his T2i. He kept shooting, heard the click, still no photo. But, when he pressed down harder (more than he had previously been doing), it worked. He doesn't know why it should require more of a "push" than before, but it works.
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Selkii, I just learnt that this happen when mirror lockup is enabled. For good measures, I disabled this option and the Viewfinder is now taking photos as normal.