[photo-3d] Re: 3D Camera Synchronisation

["Robert Brand" <rb@xxxxxxxxxx>]

Allan Griffin wrote:   My own testing indicates that your independent
processors and their independent mechanical shutter mechanisms
are no where near as "very close" as you appear to suspect.
I have found that accepted manufacturing tolerances (+ & -) can
add up to several milliseconds unless you are both very lucky
and you do everything right.

You refer to "independant processors and their independent mechanical
shutter mechanisms". In twinned cameras that are joined at the shutter
mechanism, I must point out that they still have totally independent
mechanical shutter mechanisms. Unless you cut the cameras up and do what RBT
have done with these, then the shutters are still totally separate
mechanisms and have the same issues as those joined at the shutter switch.
No difference.

Also the type of manufacturing tolerances you mention are nothing to do with
the microprocessors. They are not subject to tolerances in the same way that
mechanical items are. In simple single chip processor cameras with identical
software, if triggered at the same point in their routine, should take the
same time to do things. If we can eliminate variables as much as possible
(my earlier posting), separate processors should trigger the shutters at
almost the same time. It is then up to the mechanical aspects of the
shutters. If they are different, they will affect both twin cameras that are
sync'ed at the shutter switch as much as ones that are sync'ed at the
shutter itself. If the shutter mechanism produces eractic or delayed results
due to age or mechanical problems, that is what you will live with in both
types of sync. I do not believe enough cameras have sync'ed at the shutter
to know for sure about the reliability of the sync. Do you have significant
numbers of conversions or was this a small sample?

It also does not do twin rig cameras any good to be left for periods of time
without use. They should be exercised regularly every month to keep the
shutter mechanism (and if the motor that drives it in many cameras) free
from any stickiness that results from lack of use. I recently did not use my
Ricohs for a year and it took many weeks for them to start to get back to
normal sync. I can assure everyone that this was not due to electrical
issues - just good old mechanical stagnation. I am happy to say that the
effect does not appear to be permanent. Many people with sync problems on
Ricoh's will find improvement if the cameras are used regularly. If unused
for a period of time I suggest a firing 20 or so "blanks" before loading
film. If you have film in the cameras and they have been in storage, set the
cameras to multiple exposure and waste a frame but fire the camera 20 or so
times to get the mechanisms freed up.

Allan, thanks for the questioning mind. It keeps me "honest??" and helps get
to the heart of anything that I overlooked to mention earlier.

Finally let me say that all this aside, twinning at the shutter is a cleaner
way to go if you do not want to have the extra trouble of blocking out eye
pieces, etc. It also allows for accurate sync of auto bracketing and camera
controlled rapid shots - something connecting to the shutter switch will
never do. There are also many things they will NOT do and it comes down to a
choice of what suits you best. Just don't get comfortable with the though
that any solution is a cure-all. There are sure to be plenty of issues. I
personally would like 4 Ricohs. That would allow me to have both types of
sync. I'm off to talk to my boss about more pay....

Regards, Robert Brand


 

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