[Leica] Hotshoes on cameras w/out batteries

[leica at rcmckee.com (R. Clayton McKee)]

On 7 Jun 2005 at 12:35, Frank F. Farmer wrote:

> 1) Cameras like the M4-P have hot shoes, but no batteries to speak of.
>  How does such a camera trigger the electrical contact on the hot
> shoe?  
> 
> 2) Why was this changed on the M6TTL?  Does it have to do with the TTL
> flash meter?  
> 
> 3) Will a "classic" M6 w/out a battery trigger a flash in its hot shoe?


For a nondedicated, single-pole flash unit like a 283, all the camera 
has to do to fire the flash is close the circuit between the two 
contacts on the shoe.  It's a timing issue, no more.  That's easy to 
do with a mechanical switch.  (4Ps and before had multiple pc sockets 
because the timing lag for a bulb flash is different from that for 
electronic flash.  By the time the 6 was coming out, bulb flash was 
mostly extinct so there was no need for the M sync.  A handful of the 
very last 4P run had m6 top plates and rangefinders, and theydidn't 
have the M-sync either.  85 or 86 production here.)

When you go into TTL or even AE flash, you've got electronic control 
data being passed back and forth between the processors.  That's a 
whole other set of issues... I'm guessing even the main circuit on 
the M6TTL is electronically operated, just for the sake of design 
simplicity.  

The classic M6 has a single-contact hotshoe, as I recall; I'd bet 
lots of your money that it's mechanically triggered as well.  I don't 
have any convenient way to test that, though... both my bodies are 
4P's.


--


R. Clayton McKee                               www.rcmckee.com
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