Hi Anand,

If this is just a one-off hobby project, you can probably get by with the minimalist approach of feeding Vcc through an internal protection diode, but I would not call the method desirable/acceptable/reliable for anything I intended to sell as a product.

I would prefer to just add my own diode inline with the Vcc supply if I needed the 0.6V drop.

If you're going to use to use the 12F675, I would go with an external LP 32kHz crystal for sure. That drops your current from Fosc = 4MHz INTOSC at ~500-700uA @ 3V down to ~18-20uA @ 3V.

Then adjust WDT prescaler for whatever delays you need, and have all delays during sleep periods. I/O output levels stay the same during sleep, and that can save a ton of power. If timing isn't critical.

The stress on the low current is, because there IS no battery driving this circuit
If it's operating from the camera battery, which it appears to be, it definitely is battery powered...