Flash Sync Speed w/Hassy & Rollei

[rosts]

You could get an inexpensive hot shoe to PC cord adapter to attach your hot shoe-only transmitter to the Hasselblad's PC connection. Test this thoroughly before using film, since an old lightly used PC terminal might have dirt in it which would prevent sufficient contact to fire the flashes.

 

Thanks a lot! Yes, i guess i saw this adapter at our local store.

 

You meant this one?

 

Edited January 12, 2020 by rosts

[AJG]

Something like that, except it should have a PC cord attached to connect with your Hasselblad.

[Ed_Ingold]

A Sekonic meter is still sensitive to ambient light in flash mode. That's the only reason I can think of for the shutter speed setting to affect the exposure. There is really no way for the meter to know the shutter speed or flash characteristics.

 

The latency of a high quality radio trigger, like Pocketwizard, is low enough to use a leaf shutter at 1/500. Most flash units will work at that speed as well. A few studio flash units have durations of 1/250 second or so at full power. Check the specifications, and lower the power if necessary.

[rodeo_joe1]

On my ancient Sekonic L 718, I definitely get different readings at 1/500 than I do at 1/125 or 1/60 with my White Lightning X 3200 and 1600 studio flashes. One of the many reasons I chose that meter was that it is "gated" and combines ambient light and flash to give the exposure reading. I don't know if that is true for newer Sekonic meters as I haven't used one.

The same goes for the cheap Shepherd FM900 and 990 flash/ambient meters. They have a thumbwheel that sets a gate time between 1/60th and 1/500th s.

 

Old Quantum flash meters do the same thing. Neat little things, but with unreliable battery contacts IME.

The latency of a high quality radio trigger, like Pocketwizard, is low enough to use a leaf shutter at 1/500.

The delay on PWs has been measured to be exactly the same as, or even slightly longer than, that of most cheap Chinese radio triggers. You still need to drop the maximum synch speed of a focal-plane shutter by one or two stops to prevent a black band at the bottom of the frame. And the same delay will cause a shift of synchronisation, and consequent loss of some light, with a leaf shutter at 1/500th. The loss will be on the exponential decay curve, so not that great, but still there.

 

There's absolutely no synch delay advantage to wasting your money on PWs. You still have to wait for a Phase-locked loop circuit to gain lock on the encoding modulation frequency.

Edited January 13, 2020 by rodeo_joe|1

[rodeo_joe1]

That's the only reason I can think of for the shutter speed setting to affect the exposure.

I posted this quite recently on another thread.

It shows a typical flash output curve at full 'power'. You can easily see from the orange cumulative exposure integral curve that light is still emitted up to 9 milliseconds after the flash is triggered. That's 1/110th of a second, and well beyond the nominal 1/500th s of a leaf shutter.

 

Using the orange curve, you can work out that a 1/500th s shutter speed gathers about 70% of the total light, whereas 1/250th s collects about 90%. A very measurable difference.

Edited January 13, 2020 by rodeo_joe|1

[Jochen_S]

I guess it's not a big problem if i would use central shutter where you can sync at any shutter speed with a flash.

I used rangefinder, nominally 1/250 sync speed. According to the results I got above 1/125 sec: Some of the strobes fired in time, others too late. I had two radio triggered ones and the rest triggered via optical slaves, by those two. Maybe radio triggers on all flashes would have helped. Neither my studio, nor my real problem, so I didn't shop to try.

[Ed_Ingold]

I referred to the shutter speed setting on the flash meter, not the camera.

 

The nominal flash duration is the time the intensity is above 50% of the peak level. As the capacitor discharges, its voltage drops, which also changes the color of the flash. That's one reason to avoid long shutter durations (the most important being ambient light effect). Shutter speeds longer than the nominal flash duration add less than 1 stop to the exposure, even on bulb.

 

Flash exposure depends greatly on the environment, subject, and your photographic application. With studio flash units, eg for portraits and group photos, I make test exposures in addition to meter readings. A radio trigger, attached to the meter, facilitates this task. For on-camera flash, you take what you get, perhaps adjusting the compensation in the flash or camera. When possible, I use fill or bounce flash, with an appropriate filter on the flash head.

 

High end studio units, like ProFoto (and shoe flash units), vary the flash power by quenching the flash, which mostly maintains a constant color temperature. Inexpensive units change the voltage applied to the capacitor, hence the color. It's easy to tell, because in the latter, reducing the power setting causes (or requires) the flash to be triggered.