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OmarAl
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Posts: 21
Re: How does a Sync port work?
Good morning gentlemen,
I do apologise for my late reply! Things at home gotten in the way a bit thus slightly forgetting and making it hard to come back and get back to you wonderful people, I hope you understand!
markkuk wrote:
No. When the camera connects the two conductors of the sync port or hot shoe together the flash fires. The duration of the light is determined by the flash, not the camera.
Ahhh I see, I always thought it was the camera, especially since it goes so fast! I understand that the flash would have different intensities of light power but always at the same duration. If that's the case then, how does a flash device determine how long the light should last for? Does the light bulb itself play an important part to this??
chuxter wrote:
No.
First as someone else mentioned, the switch [either mechanical or electronic] pulls the center contact to ground. Thus, the leading edge is negative going. As I mentioned to see this, you will have to pull the line up w/ a resistance [about 5000 Ohms?] going to something like 3-10 volts.
The fall time of the leading edge is VERY short, especially w/ mechanical contacts. Even w/ an electronic switch [transistor], the fall time is probably less than a micro-second. The fall time has absolutely nothing to do w/ the duration of the flash pulse! The pulse just initiates the flash. The duration of the flash pulse is a different and lengthy discussion.
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chuxter wrote:
Yes. The center pin is generally identical to the center pin of the PC socket. There are MANY adapters on the market.
Wow, that was a bit for me to take in and trying hard to understand it too but highly appreciative for you mentioning this! As I have gathered, it is the flash device that determines the duration of the emitted light and not the camera and it all signals (either from mechanical or electronic) from the Ground contact of the hot shoe, thus if I am correct it is like across ALL cameras I suppose??
Rajraj wrote:
Good guess. There is an international standard for flash triggers. ISO 10330 "Photography — Synchronizers, ignition circuits and connectors for cameras and photoflash units — Electrical characteristics and test methods."
It states that for an electronic switch it should pull the flash's trigger voltage down to 1.5V or lower in less than a microsecond and then keep it there for at least ten microseconds. The standard recommends that the camera holds the trigger voltage at 1.5V or lower until the shutter starts to close, though.
The standard for mechanical switches is a bit more complex, since it allows for contact bounce and chatter, but the gist of it is the same; pull down to 1.5V or lower for at least ten microseconds.
That is absolutely fantastic to hear, I'll definitely be checking out ISO 10330 standard for Photography, probably can get a better sense out of it
Although still relevant, since I have a better understanding how or where the signal for the flash originates from i.e. the Ground contact (or signal within the camera?) of a hot shoe which is also technically identical to the Sync port, where does that actually go within the Flash device? What is it inside that would need for it to set the light bulb to emit??
For example, if I was to take a Flash device apart to have complete access to the circuit board, could I set off a flash by touching some pins/contacts or something like that perhaps?