Optical Slaves in Strobes

Hello all,

I was wondering what the synch speed is for most optical slaves integrated
into studio flashes. I was considering using a on camera dedicated flash as
a fill, and to set off strobes. The flashes synch much faster than the
traditional synch (1/4000 or 1/8000 depending on camera flash) versus
1/180th of a second.

Thanks!

Robert Meyers

"McLeod" wrote in message
...
On Tue, 12 Oct 2004 23:55:08 -0700, "Robert Meyers"
wrote:

Hello all,

I was wondering what the synch speed is for most optical slaves integrated
into studio flashes. I was considering using a on camera dedicated flash
as
a fill, and to set off strobes. The flashes synch much faster than the
traditional synch (1/4000 or 1/8000 depending on camera flash) versus
1/180th of a second.

Thanks!

Robert Meyers


I'm not quite sure I understand your question. If you are shooting
with 35 mm you will have to shoot at your maximum sync speed of your
camera or lower.

Your on camera flash will trigger your slaved flashes instantaneously
(but not quite at the speed of light!).

Some older flash units have quite slow sync speeds. I have used some
older Bowens Monolights that recommend a shutter speed (with medium
format) of no more than 1/400 of a second.

I don't know if this helps.

I was wondering if I could use the high speed synch for propretary flashes
to cheat
the max x-synch of the camera. This sounds like the answer is yes?

Thanks!

On Tue, 12 Oct 2004 23:55:08 -0700, "Robert Meyers"
wrote:

Hello all,

I was wondering what the synch speed is for most optical slaves integrated
into studio flashes. I was considering using a on camera dedicated flash as
a fill, and to set off strobes. The flashes synch much faster than the
traditional synch (1/4000 or 1/8000 depending on camera flash) versus
1/180th of a second.

Thanks!

Robert Meyers


I'm not quite sure I understand your question. If you are shooting
with 35 mm you will have to shoot at your maximum sync speed of your
camera or lower.

Your on camera flash will trigger your slaved flashes instantaneously
(but not quite at the speed of light!).

Some older flash units have quite slow sync speeds. I have used some
older Bowens Monolights that recommend a shutter speed (with medium
format) of no more than 1/400 of a second.

I don't know if this helps.

On Wed, 13 Oct 2004 03:38:11 -0700, "Robert Meyers"
wrote:

I was wondering if I could use the high speed synch for propretary flashes
to cheat
the max x-synch of the camera. This sounds like the answer is yes?

Thanks!

No. You cannot cheat the max x-sync of your camera with studio
flashes. HSS is a different beast altogether.

On Wed, 13 Oct 2004 03:38:11 -0700, "Robert Meyers"
wrote:

I was wondering if I could use the high speed synch for propretary flashes
to cheat
the max x-synch of the camera. This sounds like the answer is yes?

Thanks!

No. You cannot cheat the max x-sync of your camera with studio
flashes. HSS is a different beast altogether.

"Robert Meyers" wrote in
:

"McLeod" wrote in message
...
On Tue, 12 Oct 2004 23:55:08 -0700, "Robert Meyers"
wrote:

Hello all,

I was wondering what the synch speed is for most optical slaves
integrated into studio flashes. I was considering using a on camera
dedicated flash as
a fill, and to set off strobes. The flashes synch much faster than
the traditional synch (1/4000 or 1/8000 depending on camera flash)
versus 1/180th of a second.

Thanks!

Robert Meyers


I'm not quite sure I understand your question. If you are shooting
with 35 mm you will have to shoot at your maximum sync speed of your
camera or lower.

Your on camera flash will trigger your slaved flashes instantaneously
(but not quite at the speed of light!).

Some older flash units have quite slow sync speeds. I have used some
older Bowens Monolights that recommend a shutter speed (with medium
format) of no more than 1/400 of a second.

I don't know if this helps.

I was wondering if I could use the high speed synch for propretary
flashes to cheat
the max x-synch of the camera. This sounds like the answer is yes?


Depends what you're trying to do, but for the most part, the answer
is "no".

Maximum sync speed on most cameras is determined by the shutter
mechanism, and has nothing to do with the flash. The shutter curtains (that
open to expose the film) can only move so fast physically.

There are two shutter curtains in most SLRs, and they both move the
same direction across the film - one opens, say moving left to right, and
the other closes in the same direction, following it. For high shutter
speeds, the first one doesn't even open all the way before the second one
starts to close, and they both move across the film at the same time. The
gap between them is the actual shutter speed, but the film never gets
exposed all at once - it's actually exposed by a slit between the curtains
that passes across the film.

Flash durations are usually extremely brief, much shorter than the
shutter speeds. So when they go off, they only expose the portion of the
film currently uncovered by the shutter curtains, and what you get is a
narrow band on the film that's properly lit - the rest is underexposed.

So maximum sync speeds are actually the highest speed the camera can
manage where both curtains are open all the way at the same time - it
pretty much tells you how fast the curtains can move.

High Speed Sync flashes are made to go off several times in rapid
succession, carefully timed to illuminate each patch of film as that slit
travels. This is pretty hard to get around - it requires precision
communication between camera and flash.

However, this would not stop you from locking the shutter open for a
longer period and using the flash as the sole illumination for the image -
for instance, in a very dark room. How you might accomplish this is up to
you, but the method of flash metering has to be taken into consideration.

Hope this helps. Good luck!


- Al.

--
To reply, insert dash in address to match domain below
Online photo gallery at www.wading-in.net

"Robert Meyers" wrote in
:

"McLeod" wrote in message
...
On Tue, 12 Oct 2004 23:55:08 -0700, "Robert Meyers"
wrote:

Hello all,

I was wondering what the synch speed is for most optical slaves
integrated into studio flashes. I was considering using a on camera
dedicated flash as
a fill, and to set off strobes. The flashes synch much faster than
the traditional synch (1/4000 or 1/8000 depending on camera flash)
versus 1/180th of a second.

Thanks!

Robert Meyers


I'm not quite sure I understand your question. If you are shooting
with 35 mm you will have to shoot at your maximum sync speed of your
camera or lower.

Your on camera flash will trigger your slaved flashes instantaneously
(but not quite at the speed of light!).

Some older flash units have quite slow sync speeds. I have used some
older Bowens Monolights that recommend a shutter speed (with medium
format) of no more than 1/400 of a second.

I don't know if this helps.

I was wondering if I could use the high speed synch for propretary
flashes to cheat
the max x-synch of the camera. This sounds like the answer is yes?


Depends what you're trying to do, but for the most part, the answer
is "no".

Maximum sync speed on most cameras is determined by the shutter
mechanism, and has nothing to do with the flash. The shutter curtains (that
open to expose the film) can only move so fast physically.

There are two shutter curtains in most SLRs, and they both move the
same direction across the film - one opens, say moving left to right, and
the other closes in the same direction, following it. For high shutter
speeds, the first one doesn't even open all the way before the second one
starts to close, and they both move across the film at the same time. The
gap between them is the actual shutter speed, but the film never gets
exposed all at once - it's actually exposed by a slit between the curtains
that passes across the film.

Flash durations are usually extremely brief, much shorter than the
shutter speeds. So when they go off, they only expose the portion of the
film currently uncovered by the shutter curtains, and what you get is a
narrow band on the film that's properly lit - the rest is underexposed.

So maximum sync speeds are actually the highest speed the camera can
manage where both curtains are open all the way at the same time - it
pretty much tells you how fast the curtains can move.

High Speed Sync flashes are made to go off several times in rapid
succession, carefully timed to illuminate each patch of film as that slit
travels. This is pretty hard to get around - it requires precision
communication between camera and flash.

However, this would not stop you from locking the shutter open for a
longer period and using the flash as the sole illumination for the image -
for instance, in a very dark room. How you might accomplish this is up to
you, but the method of flash metering has to be taken into consideration.

Hope this helps. Good luck!


- Al.

--
To reply, insert dash in address to match domain below
Online photo gallery at www.wading-in.net

"Robert Meyers" wrote:
I was wondering if I could use the high speed synch for propretary flashes
to cheat the max x-synch of the camera. This sounds like the answer
is yes?

No. What HSS does is keep the flash on _longer_, so that it continues
to illuminate the subject while the "slit" between the front and rear
curtains travels across the sensor (digital or film).

If you were to use HSS to trigger a typical monolight, you'd end up
with a stripe (probably horizontal) that's fully exposed; the rest
of the shot would show varying degrees of underexposure.

What's the shooting situation where you envision requiring high
shutter speeds?

Different systems offer various options for off-camera HSS, but they
all require dedicated flash units. To be honest, I played with HSS
when I first got my F100 and haven't used it since. If a situation
requiring a high shutter speeds and mix of natural and off-camera
lighting arose tomorrow, I'd either rent a continuous fluorescent
light or use a medium format camera with a leaf shutter lens.

--
Michael Benveniste --
Spam and UCE professionally evaluated for $419. Use this email
address only to submit mail for evaluation.

"Robert Meyers" wrote:
I was wondering if I could use the high speed synch for propretary flashes
to cheat the max x-synch of the camera. This sounds like the answer
is yes?

No. What HSS does is keep the flash on _longer_, so that it continues
to illuminate the subject while the "slit" between the front and rear
curtains travels across the sensor (digital or film).

If you were to use HSS to trigger a typical monolight, you'd end up
with a stripe (probably horizontal) that's fully exposed; the rest
of the shot would show varying degrees of underexposure.

What's the shooting situation where you envision requiring high
shutter speeds?

Different systems offer various options for off-camera HSS, but they
all require dedicated flash units. To be honest, I played with HSS
when I first got my F100 and haven't used it since. If a situation
requiring a high shutter speeds and mix of natural and off-camera
lighting arose tomorrow, I'd either rent a continuous fluorescent
light or use a medium format camera with a leaf shutter lens.

--
Michael Benveniste --
Spam and UCE professionally evaluated for $419. Use this email
address only to submit mail for evaluation.

Robert Meyers wrote:

Hello all,

I was wondering what the synch speed is for most optical slaves integrated
into studio flashes. I was considering using a on camera dedicated flash as
a fill, and to set off strobes. The flashes synch much faster than the
traditional synch (1/4000 or 1/8000 depending on camera flash) versus
1/180th of a second.

1) Studio strobes 'dump' all of the power in the caps when triggered. The
power level chosen sets the amount of cap charging. At low power settings, a
studio strobe dumps in about 1/10,000 to 1/1,000 of a second, at high power
settings, it might be as much as 2 ms. Leaf shutter lenses typically go up to
1/500 so it is a convenient fit. (Some leaf shutters go even faster). Needless
to say, the shutter needs to be fully open when the strobe fires.

The optical signal from the camera strobe to the slave travels about 1 foot per
nanosecond. So negligible. The trigger time from receiving the pulse to
closing the circuit at the slave is less than a microsecond. Negligible.

In short, to use the studio strobes, you must operate your camera at its sync
speed or slower regardless of the sync speed capability of the attachment flashes.

2) 1/4000 (1/8000) synch is really not sync'd at all. Often called High Speed
Sync (HSS), the flash is modulated to output a long series of tiny bursts while
the shutter 'slit' is in movement. The flash actually begins firing before the
first shutter begins moving and is still firing after the rear curtain gets to
the other side. During travel, tiny bursts of light are fired.
http://www.photozone.de/bindex3.html

This is highly inefficient as part (sometimes most) of the 'return' light is
falling on the shutter curtains not film, making a GN 56 m flash into a GN 3 m
flash at 1/8,000.

Again, you cannot use the HSS mode as fill if the shutter speed is above the
sync speed of the shutter if you are triggering studio lights as well.

3) Wireless HSS
On Minolta cameras and flashes, off camera HSS is available (Maxxum 7,
3600HS/5600HS flash).

In the end, HSS is not that useful that often.

Cheers,
Alan
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