High-Speed Sync for Speed Graphic

[AeroK]

I want to use a strobe in conjunction with the focal-plane shutter in my Speed Graphic. Normally, one uses slow-burn flashbulbs because the shutter has vertically sliding slots -- different widths for different speeds. Regular strobes are way too fast and therefore only expose a small part of the frame.

High-speed sync simulates a slow-burn flashbulb by firing many times in rapid succession while the focal-plan shutter wipes across the film.

My question is: Has anyone figured out to connect the Speed Graphic's flash contacts to a strobe (or trigger) for high-speed sync with anything like Godox or any other strobes?

...doug

[Tin Can]

https://www.bhphotovideo.com/c/produ...to_Bipost.html

However they are a tight and hard fit

I think you need to use slow shutter speeds and let the flash stop the action

I sometimes shoot without lights on

[Oren Grad]

Physically connecting the flash should be simple enough with a bipost sync cord. I think what you need to find out is the travel time of the SG shutter curtain at different tension settings compared to the travel time of the small, bladed focal plane shutters in modern SLR and mirrorless cameras for which HSS has been promoted. My guess is that the Speed Graphic curtain will be way too slow, that the HSS flash pulse sequence won't last nearly long enough to cover it. And if it does, the power will probably be so attenuated that it's not especially useful. But it's a great question, I too would like to hear about it if someone has found a way to make it work.

[AeroK]

I too would like to hear about it if someone has found a way to make it work.

I need to dig into the wiring of HSS strobes. It's probably not something as simple as a contact closure, but it might be possible to control it with an Arduino or something like that. I fear you're right, Oren -- that HSS won't last long enough for the relatively slow shutter speeds of the focal-plane shutter.

[Oren Grad]

I need to dig into the wiring of HSS strobes. It's probably not something as simple as a contact closure...

It might be. If the HSS setting is made on the flash rather than from the camera's menu, and the exposure mode is set for manual or for AE controlled via on-flash sensor rather than camera-controlled TTL AE, there might not be anything that needs to be communicated between camera and flash other than sync closing. In theory the duration of the HSS pulse sequence might be customized to different camera bodies via some signal through the dedicated flash contacts, but in practice I suspect that it's a fixed parameter.

[AeroK]

...if the HSS setting is made on the flash rather than from the camera's menu, and the exposure mode is set for manual or for AE controlled via on-flash sensor rather than camera-controlled TTL AE, there might not be anything that needs to be communicated between camera and flash other than sync closing. In theory the duration of the HSS pulse sequence might be customized to different camera bodies via some signal through the dedicated flash contacts, but in practice I suspect that it's a fixed parameter.

Just a guess, but I would think the manufacturer would design a system in which the strobe was aware of the shutter speed so it didn't have to keep flashing once the shutter was fully closed. Big difference between asking the strobe to cover 1/500 seconds versus 1/8000.

[Tobias Key]

Just a guess, but I would think the manufacturer would design a system in which the strobe was aware of the shutter speed so it didn't have to keep flashing once the shutter was fully closed. Big difference between asking the strobe to cover 1/500 seconds versus 1/8000.

I don't think that is what happens. The shutter always takes the maximum sync speed (say 1/250th) to open then fully close at high speeds. The slit between the shutters (the shutter is never fully open at higher speeds) creates the higher shutter speeds. So the burn of the HSS flash is always 1/250th or whatever but at higher speeds the maximum power is cut as the gap between the shutters narrows. The shutter curtains themselves always travel at the same speed it's the timing of the second curtains release that controls shutter speed. So what you would need to look for is a flash that burns for the amount of time it takes for the the speed graphic shutter to fully open and fully close. I don't know how long that takes with a speed graphic but if it takes 1/30 with a Pentax 67 I would guess it would take a 1/15 or an 1/8 second with a Speed. I don't know where you would find a flash that burns for that long.

[Oren Grad]

Just a guess, but I would think the manufacturer would design a system in which the strobe was aware of the shutter speed so it didn't have to keep flashing once the shutter was fully closed. Big difference between asking the strobe to cover 1/500 seconds versus 1/8000.

So what you would need to look for is a flash that burns for the amount of time it takes for the the speed graphic shutter to fully open and fully close. I don't know how long that takes with a speed graphic but if it takes 1/30 with a Pentax 67 I would guess it would take a 1/15 or an 1/8 second with a Speed. I don't know where you would find a flash that burns for that long.

What Tobias said. The relevant parameter isn't the marked shutter speed, it's the curtain travel time, because that's the duration during which some part of the sensor or film is being exposed.

[AeroK]

...the shutter always takes the maximum sync speed (say 1/250th) to open then fully close at high speeds. The slit between the shutters (the shutter is never fully open at higher speeds) creates the higher shutter speeds.

That makes sense Tobias. I think you're probably right. Thanks.

...doug

[AeroK]

...the shutter always takes the maximum sync speed (say 1/250th) to open then fully close at high speeds...So what you would need to look for is a flash that burns for the amount of time it takes for the the speed graphic shutter to fully open and fully close.

I'm still on my first cup of coffee for the day, but how about this: Assuming Tobias is correct and that the total duration of the HSS flashes are within a 1/250-second window, then I should be able to use the Speed Graphic's focal-plan shutter at 1/250 or faster. I just need to figure out how to trigger the flash. Might start experimenting today. ...doug