Thoughts on Trailing Curtain Sync

[Joseph McAllister]

On Jul 2, 2010, at 13:53 , John Sessoms wrote:

> The K-10D and K-20D both allow you to set the on-board flash to  
> trailing curtain sync. How difficult would it be for them to make  
> the hot-shoe also fire on the trailing curtain when a non-dedicated  
> "flash" is installed?
>
> E.G. like with a radio-sync transmitter or Vivitar 285HV? Dedicated  
> flash like the AF-540FGZ has its own circuitry to talk to the camera  
> and can be set to trailing curtain sync.
>
> Is this something they could do with a firmware update?
>
> Or is it something that would require radical hardware revision?
>
> For that matter what do the dedicated pins on the Pentax shoe tell  
> the flash? I know what the big one in the center does, and it's  
> obvious which one is ground.


Everything you need to know except the actual format and content of  
the "digital" signal and the "mode" format.

http://kmp.bdimitrov.de/technology/hot-shoe/index.html

Here's a diagram of a circuit to isolate an old high voltage flash  
from the hot shoe about half way down the page. I know, you didn't  
ask, but, it can't hurt to have a copy on your hard drive!

http://www.flickr.com/groups/strobist/discuss/72157607929201242/

And the Hot Shoe and 5P cable pins, in case you wanted to know. Near  
bottom of page.

http://forums.dpreview.com/forums/read.asp?forum=1036&message=28607959

Lots and lots of data about the Pentax AFxxxFGZ flashes compared to  
others manufacturers.

http://knol.google.com/k/pentax-p-ttl-hot-shoe-flash-comparison#

also a more technical tome:

http://www.jr-worldwi.de/photo/index.html?ist_DS_internalflash.html

Joseph McAllister
pentaxian at mac.com

THE SENILITY PRAYER :
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The good fortune to run into the ones I do, and
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