So is there any way to make the release a totally safe issue, that means: a one-contact-release only?
What you are asking for is quite difficult physically. You are trying to make two discrete things happen (focus & shoot) in sync between two cameras with only one signal event.
One way around this is to use a script that initiates the set focus & exposure actions when the one-contact-release happens and also starts a timer. If you can show in the controlled environment of your scanner that the cameras will always complete the focus/exposure operations within a fixed time interval like 2 seconds or less, then the script will wait for that long and then release the actual shot. This is easy to do but means that you will always have that delay to wait for prior to turning the page.
Could I achieve this , if I disable autofocus (I unterstand, that CHDK can make me focus manually?)? Or would this bring me only closer, that is, make the delay shorter, but still depended on the time, that the camera needs to adjust?
That would help a lot - both cameras would fire within a few hundred milliseconds of each other at worst (my guess).
Otherwise the only possibility I see would be a second circuit with a time switch, to make sure about a constant release.
That would be even better - but the script method I mentioned above would do the same thing for "free".
This seems like a good application for the "hold down half press, click full" approach.
...
Waterwingz probably has a better idea of how to accomplish this using the remote code.
This came up a few months ago. It would be quite easy to add an output control module to the USB remote code to do this. The only messy part would be deciding when to release the "half press". After a user defined delay ( range 10 seconds to two minutes maybe ?) Or maybe after two quick USB remote presses to indicate a cancel ( less that 0.5 seconds apart)?
Edit : what about USB=5V initiates the half press and then USB=0V goes to full press. If you then re-assert the 5V within 2 seconds, the sequence continues with half press held. Otherwise the half press is released and everything resets.
Could anyone give me a short idiots guide of how to arrive at my goal to focus manually? I've found the MF-test sheet, where the a2300 is listed. But i have no idea, what this means. Actually i also don't know how to get a script running.
You can set focus manually using the CHDK menus. This is described in the
CHDK Manual : Override Subject DistanceAs far as scripting goes, there is lot's of good stuff about scripting here :
CHDK Scripting Cross Reference including some good links at the top of that page.
There is also the scripting section in the
CHDK Manual : ScriptingThe script function you are looking for is
set_focus(). Please note that the ability to accurately set focus seems to depend on the camera model and to a lesser extent on differences between the same model of camera. Testing will be required to make sure it works to your satisfaction.
If you'd like me to cobble together a script for you that does what we have discussed here just let me know.
