2

What's the technical challenge here? Is it more of a marketing decision to encourage you to pay more for TTL based models (let's disregard other advantages of TTL for the moment). If we can have flash with high enough burst frequency we should be able to fill the frame regardless of the shutter speed or 'slit height' right? Feel free to go as technical as you need, I can handle that. Thanks in advance.

6

The problem that is solved via high speed sync has nothing to do with the power of the flash and everything to do with the curtain transit time of the camera. Above a camera's sync speed the second curtain begins to close before the first curtain is completely open. Therefore very precisely timed multiple flashes must be emitted from the flash as the open slit between the two curtains moves across the film/sensor plane. Manual flashes are not capable of this precision because they are not capable of two way communication between the camera and flash. The are only capable of receiving a single command to fire.

HSS requires the pulses from the flash to be timed to the particular shutter speed selected and must also take the camera's shutter transit time into account. Transit times and sync speeds vary from one camera to the next. Even if the flash could be manually set to the shutter speed selected in the camera, how would a manual flash with only a fire communication capability know the precise shutter transit time and thus be able to calculate the timing of the pulses needed? Then there's even the issue that one camera's 1/500 second may actually be 1/478 second and another camera's may be 1/511 second.

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    hey thanks for taking your time. I understand the technicality at work here. I think you misinterpreted. I didn't say anything about power. I said 'high enough burst frequency'. Here's what I was thinking. Lets say we're firing at 2000th of a second. Our camera can do 250th as its max 'native speed'. So the slit height is 16mm at 250th (assuming its an APS model. 24mm for full frame 35). As we go from 250th to 2000th our slit height becomes 1/8 or 2mm. That means if we can fire 8 flash pulses within 250th of a second, or 32 times in one second, we should be able to fill the frame right? – zeebazu Jan 8 '15 at 14:26
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    @zeebazu That comment aside, though, the basic answer is here: the standard manual flash interface just has one switch and no communication, so it's impossible to coordinate this. And if you add more complicated communication, there's little advantage in not going all the way to a full camera-driven-TTL flash. – mattdm Jan 8 '15 at 14:33
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    @zeebazu: Eight pluses within 1/250th would be 2,000 pulses per second. – Blrfl Jan 8 '15 at 14:38
  • Thanks mate, you're absolutely right. 2 Khz pulse. What a stupid calculation mistake to make! For some reason I mixed 1/250th with 250 millisecond, no idea why! – zeebazu Jan 8 '15 at 14:45
  • @mattdm okay that makes sense. To add a high frequency PWM based pulsing system, the cost addition means its just simply wiser to pay little extra and get a full blown ttl model with all the extra goodies that come along with it. thanks again, both of you. NOW I am wondering why don't we have flashes with motorized head to change light angle remotely (not zoom) and flashes that can remotely alter their color temperature lol! That's a question for another day. Cheers guys. Since I am not registered, I can't seem to 'thumbs up' your comments :\ – zeebazu Jan 8 '15 at 14:56
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Godox has several lines of flashes (everything from speed lights to studio strobes) that are manual with HSS. The challenge is HSS requires the trigger interface with the cameras proprietary flash protocols and so if you're doing all that you might as well do TTL. Godox gets around this by making HSS an off-camera only function. So the flash has a single firing pin but if if you use the right radio trigger the flashes will utilize HSS with a variety of cameras.

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Back in the day I had a camera that selected between Flash bulb and the then new electronic flash. The Flash bulb didn't have a brain nob did it need to communicate with the camera. It was that the Bulb would be instructed to fire as the first curtain began its travel and would burn longer covering the duration of the exposure.

The original question is still valid. If the flash is set to have a specific duration of 1/250 second then it is only a matter of timing the initial start of the burst.

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