Film vs. Digital... Die, Die, Die! (was: VCF suggestions...

[Tony Duell]

> My Contax RTS, which is at least 30 years old, needs a battery to
> release the shutter.

I don't dispute there were electronic cameras going back about 40 years. 
But fully mechnnical ones exist too. There have even been automatic 
exposure cameras that don't use a battery... (Contact me off list if you 
want to know about lock-needle mechanisms and a strange camera with a 
pneumatically-timed shutter).

> 
>  Tony> Mroe seriously, the batteries taken by most film cameras were
>  Tony> standard primary batteries and are a lot easier to find than a
>  Tony> custom Li-ion or NiMH pack for a digital camera.
> 
> I forgot what the Contax needs.  A primary battery for sure, but I
> don't think it's one of the usual AA or such.

Most electronic cameras need either 3V or 6V. Some of the later ones with 
motors use AA or AAA cells, the ones that just use the battery for the 
meter and chutter control often use silver oxide batteries.

> 
> It might be as bad as a set of nice microphones I have (Signet) --
> which require an 8 volt mercury battery.  Seriously not PC, and hard
> to find even 10 years ago, probably completely nonexistent now.

AFAIK Mercury cells are no longer made :-(

Some older cameras had a fairly simple exposure meter circuit that 
depended on a constant and known battery voltage (which was the case with 
a mercury battery). Put a modern alkaline cell in there and you get the 
wrong exposure. 

Others used a bridge circuit, with the correct exposure being the balance 
point of the bridge. These are independant of battery voltage [1] so it's 
relatively easy to keep them going now.

[1] Well some of these cameras had the meter scaled either side of the 
balance point for 1 stop over/under exposure. This won't be accurate if 
you use a non-mercury battery, but there's a trivial and obvious workaround.

Pentax (idiots!) made a camera with a bridge circuit where the correct 
exposure was just off balance. The official reasone was so that if the 
battery was dead you didn't get the pointer on the correct-exposure mark. 
But of course this thing depends on the right battery voltage.

More modern electronic cameras tend to include voltage regulator circuits 
anyway.

-tony