580EX Stroboscopic question

[dwdallam]

In the manual, the 580ex explains that you set the Hz for how many flashes per second, then the next setting is for how many flashes, and then the next setting is for flash intensity.

I don't understand the difference between flashes per second and flashes.

"You can set the firing frequency (number of flashes per sec. expressed a
Hz), the number of flashes, and the flash output."

One thing Canon manual are--very concise. So concise that they sometimes are indecipherable!

What I've been doing is simply setting the Hz per second, leaving the middle setting blank, and using bulb to fire the shutter. Works fine, but I'm wondering what the middle setting actually does. I've set it to two or three and get no difference in my results.

[David Sutton]

I took it to mean the total number of flashes (up to a maximum of 10) So if you set the frequency to 4Hz, and the number to 8, you should end up with the shutter opening for 2 seconds. I can't believe how instruction manuals nowadays have turned into such weighty tomes.
Cheers, David

[David Sutton]

No, I've got it wrong again I think. The maximum number of flashes depends on the power output. So if the output is 1/4, you may only get 2 flashes. But at 1/32 power you may get 20 flashes. The 10 maximum refers to how many times you can try this without resting the flash in between.
David

[wollom]

No, I've got it wrong again I think.
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I think both posts are close Taquin.

"Frequency" is a measure of "cycles per second" or Hertz (Hz). So 10 Hz means 10 cycles per second. 5 Hz means 5 cycles per second.  Etc.
Number of Flashes is the number of times the 580 will flash.

For example,  10Hz & 5 flashes means the 580 will do multiple flashes at a intervals quick enough to do 10 flashes per second but will only do 5 flashes ie. 5 flashes in half a second.

Of course the power output must be low enough to allow the 580 to recharge enough for 5 flashes in half a second.

The camera shutter speed you set determines how many flashes are captured.  In the example above a shutter speed of half a second will 'see' all 5 flashes. A shorter exposure would 'miss' some flashes.

But I'm not sure I've made things any clearer...
Wollom

[dwdallam]

I think both posts are close Taquin.

"Frequency" is a measure of "cycles per second" or Hertz (Hz). So 10 Hz means 10 cycles per second. 5 Hz means 5 cycles per second.  Etc.
Number of Flashes is the number of times the 580 will flash.

For example,  10Hz & 5 flashes means the 580 will do multiple flashes at a intervals quick enough to do 10 flashes per second but will only do 5 flashes ie. 5 flashes in half a second.

Of course the power output must be low enough to allow the 580 to recharge enough for 5 flashes in half a second.

The camera shutter speed you set determines how many flashes are captured.  In the example above a shutter speed of half a second will 'see' all 5 flashes. A shorter exposure would 'miss' some flashes.

But I'm not sure I've made things any clearer...
Wollom
[a href=\"index.php?act=findpost&pid=198731\"][{POST_SNAPBACK}][/a]

What's the difference between number of flashes in Hz and "number of flashes?" And you can lave the number of flashes blank and you get a number of flashes equal to the Hz setting. Try this: Put your camera on bulb and set the power to it's lowest on flash, and Hz to 5. It just keeps firing as long as your finger is on the button.

[David Sutton]

What's the difference between number of flashes in Hz and "number of flashes?" And you can lave the number of flashes blank and you get a number of flashes equal to the Hz setting. Try this: Put your camera on bulb and set the power to it's lowest on flash, and Hz to 5. It just keeps firing as long as your finger is on the button.
[a href=\"index.php?act=findpost&pid=198937\"][{POST_SNAPBACK}][/a]

My manual says:
If you set the power to the lowest setting and the firing frequency to between one and five Hz (flashes per second) you will have a maximum of 100 flashes before it gives up (you didn't keep your finger on the button long enough!).
However, if you set the frequency to say, twenty Hz, the maximum number falls to 40 flashes.

Here's an example:
Say you are photographing someone doing a long jump. You want six images on the photo showing them leaving the ground on one side, travelling through the air and landing on the other. So you set the number of flashes to six.
Beforehand, you timed how long the jump lasts, and it is two seconds. Two seconds divided by six flashes equals three flashes per second.
So you dial in 3 Hz.
Cheers, David

[dwdallam]

My manual says:
If you set the power to the lowest setting and the firing frequency to between one and five Hz (flashes per second) you will have a maximum of 100 flashes before it gives up (you didn't keep your finger on the button long enough!).
However, if you set the frequency to say, twenty Hz, the maximum number falls to 40 flashes.

Here's an example:
Say you are photographing someone doing a long jump. You want six images on the photo showing them leaving the ground on one side, travelling through the air and landing on the other. So you set the number of flashes to six.
Beforehand, you timed how long the jump lasts, and it is two seconds. Two seconds divided by six flashes equals three flashes per second.
So you dial in 3 Hz.
Cheers, David
[a href=\"index.php?act=findpost&pid=199034\"][{POST_SNAPBACK}][/a]

OK so why not leave the number of flashes blank, set the Hz for three flashes and set your aperture to 2 seconds?  See that's what I don't get. You don't need to set the No. of flashes to get the same effect.

Maybe I should rephrase my problem:

If I want a shutter speed to 2 seconds and I want 3 flashes per second, I can simply dial in 3Hz and use a two second shutter speed, or leave the shutter open with bulb for as long as I need if I don't or can't time the total event time. So, that leaves me asking--What is the function of "number of flashes" ?

[David Sutton]

Uh, I find myself interested in this but never going to use it. I must keep taking the pills.

OK so why not leave the number of flashes blank, set the Hz for three flashes and set your aperture to 2 seconds?  See that's what I don't get. You don't need to set the No. of flashes to get the same effect.

[a href=\"index.php?act=findpost&pid=199046\"][{POST_SNAPBACK}][/a]

Sure, I can't see why this wouldn't work if you are shooting on manual.
Now for some conjecture. What if you have the camera set to Av or P ? Also to take my example above, the photo would be framed for exactly six flashes. Setting the shutter speed to two seconds may be no guarantee of not getting five or seven flashes, especially if the batteries on the camera or flash are getting low.
I guess it comes down to what works reliably for you. David

[dwdallam]

Uh, I find myself interested in this but never going to use it. I must keep taking the pills.

Sure, I can't see why this wouldn't work if you are shooting on manual.
Now for some conjecture. What if you have the camera set to Av or P ? Also to take my example above, the photo would be framed for exactly six flashes. Setting the shutter speed to two seconds may be no guarantee of not getting five or seven flashes, especially if the batteries on the camera or flash are getting low.
I guess it comes down to what works reliably for you. David
[a href=\"index.php?act=findpost&pid=199053\"][{POST_SNAPBACK}][/a]

You mean that settings actually will increase your shutter for as long as it takes to get all the flashes in?

[David Sutton]

You mean that settings actually will increase your shutter for as long as it takes to get all the flashes in?
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Just tried this on a 40D. No, the settings do not override the camera shutter. There goes that theory.

[dwdallam]

Just tried this on a 40D. No, the settings do not override the camera shutter. There goes that theory.
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So that's what you were thinking? If so, we're back to square one.

[David Sutton]

So that's what you were thinking? If so, we're back to square one.
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Not really. I did notice that if I wanted a certain number of flashes it was really convenient to just dial it in and set the camera to bulb and release the shutter when the flash stopped. No math involved.  
David

[wollom]

No, the settings do not override the camera shutter.
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Howdy. Just confirming, in Multi mode the flash frequency (Hz) and number of flashes are independent of the camera shutter speed. (changing the shutter speed does not change the settng on the flash)

Why?
I'd say this comes down to how you might use the Multi mode.  I'm not sure if you've shot pics in this mode - lots of stuff happens faster than you'd think, and, too many flashes on one exposure can muddle the image, (and often you'll be trying to control and ambient exposure too).

For example: photograph someone skipping/jumping rope in daylight.
1. The ambient exposures (for example) is 1/30 sec @f4. (reduce the exposure a bit so the effect of the flash will be visible) Actual exposure 1/30 @f5.6
2. Set the flash output power.  Let's say 1/64 power looks right.
3. Set the flash frequency. 30hz means only one flash will be captured. 180hz means 6 flashes captured.
4. Try out varying the number of flashes. Maybe 6 flashes mushes too many images together.  Maybe 2 falshes looks like a mistake.  4 flashes looks good.
5. Go for the shot.  The flash might keep up with the camera for 2 or 3 frame bursts; Bzzt, Bzzt.... Bzzt,Bzzt,Bzzt.... Bzzt.....

Now if you really want to do your head in...  Mutli flashes at the same power can look a bit boring.  What about a second flash with different settings? A third? Coloured gels?

Cheers

Wollom

[dwdallam]

Not really. I did notice that if I wanted a certain number of flashes it was really convenient to just dial it in and set the camera to bulb and release the shutter when the flash stopped. No math involved.  
David
[a href=\"index.php?act=findpost&pid=199157\"][{POST_SNAPBACK}][/a]

OK so you mean dial in the Hz and use bulb like i was doing? But we still are not any closer to understanding "number of flashes."

[dwdallam]

Howdy. Just confirming, in Multi mode the flash frequency (Hz) and number of flashes are independent of the camera shutter speed. (changing the shutter speed does not change the settng on the flash)

Why?
I'd say this comes down to how you might use the Multi mode.  I'm not sure if you've shot pics in this mode - lots of stuff happens faster than you'd think, and, too many flashes on one exposure can muddle the image, (and often you'll be trying to control and ambient exposure too).

For example: photograph someone skipping/jumping rope in daylight.
1. The ambient exposures (for example) is 1/30 sec @f4. (reduce the exposure a bit so the effect of the flash will be visible) Actual exposure 1/30 @f5.6
2. Set the flash output power.  Let's say 1/64 power looks right.
3. Set the flash frequency. 30hz means only one flash will be captured. 180hz means 6 flashes captured.
4. Try out varying the number of flashes. Maybe 6 flashes mushes too many images together.  Maybe 2 falshes looks like a mistake.  4 flashes looks good.
5. Go for the shot.  The flash might keep up with the camera for 2 or 3 frame bursts; Bzzt, Bzzt.... Bzzt,Bzzt,Bzzt.... Bzzt.....

Now if you really want to do your head in...  Mutli flashes at the same power can look a bit boring.  What about a second flash with different settings? A third? Coloured gels?

Cheers

Wollom
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Sounds good. You point out an important aspect of this situation too by using 1/30 instead of one second, with ambient light, which means you will have to set the shutter.

But what about "number of flashes?"

[dwdallam]

Sounds good. You point out an important aspect of this situation too by using 1/30 instead of one second, with ambient light, which means you will have to set the shutter.

But what about "number of flashes?"
[a href=\"index.php?act=findpost&pid=199194\"][{POST_SNAPBACK}][/a]

Are we giving up on this question?

[timhurst]

Are we giving up on this question?
[a href=\"index.php?act=findpost&pid=199865\"][{POST_SNAPBACK}][/a]

It simply means it will stop once it has flashed x number of times.

i.e:

display reads: 1/128__10--__1Hz
in plain english: 1 pop per second at 1/128 power for 10 pops

display reads: 1/32__5--__10Hz
in plain english: 10 pops per second at 1/32 power for 5 pops


It's up to you to keep the shutter open long enough to record all the pops you want while balancing against ambient exposure. Which is why it's easiest to shoot in the dark using bulb.

[wollom]

Which is why it's easiest to shoot in the dark using bulb.
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Tim, that's a good clear explanation of the 'number of flashes'

The great thing about this setting is that it doesn't require the bulb/blackout thing.  It's portable, flexible, and with several units working together, powerful enough for multi pop on the fly.  Something that [a href=\"http://en.wikipedia.org/wiki/Harold_Eugene_Edgerton]Harold Edgerton[/url] could only have dreamed about in 1937.

Cheers

Wollom

[dwdallam]

It simply means it will stop once it has flashed x number of times.

i.e:

display reads: 1/128__10--__1Hz
in plain english: 1 pop per second at 1/128 power for 10 pops

display reads: 1/32__5--__10Hz
in plain english: 10 pops per second at 1/32 power for 5 pops
It's up to you to keep the shutter open long enough to record all the pops you want while balancing against ambient exposure. Which is why it's easiest to shoot in the dark using bulb.
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Hey Tim, that was pretty much what I was seeing through experimenting, but the manual doesn't connect BULB and # of flashes. I keep wondering why these manuals are so cryptic?

I can see now that the # of flashes give you the ability to have a really fast Hz w/o using the entire shutter time, that is, w/o having to strobe the entire time. But I was wondering if you could offer some explanation as to how these two things work in concert with one another, with examples like you gave above? You know, some practical application that would dictate why you would want 10 flashes per second (10Hz) and then want only 5 total flashes? Off the top of my head I would say the one reason would be something like a very fast moving object--maybe a humming birds wings, but you don't want the strobes going off anymore than three times because it would blow the image?

Thanks again.

[timhurst]

Hey Tim, that was pretty much what I was seeing through experimenting, but the manual doesn't connect BULB and # of flashes. I keep wondering why these manuals are so cryptic?
[a href=\"index.php?act=findpost&pid=200009\"][{POST_SNAPBACK}][/a]

Well they aren't really connected at all. Strobe mode is just a form of manual mode so anything you set up on the flash is independent of anything you do on the camera. There's no TTL going on here but obviously the settings on either camera or flash will combine to influence the exposure. Save yourself some headaches and run the camera in manual when using the strobe mode.

I can see now that the # of flashes give you the ability to have a really fast Hz w/o using the entire shutter time, that is, w/o having to strobe the entire time. But I was wondering if you could offer some explanation as to how these two things work in concert with one another, with examples like you gave above? You know, some practical application that would dictate why you would want 10 flashes per second (10Hz) and then want only 5 total flashes? Off the top of my head I would say the one reason would be something like a very fast moving object--maybe a humming birds wings, but you don't want the strobes going off anymore than three times because it would blow the image?
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I think you've pretty much got it. The frequency (Hz) allows you to match up to what your subject is doing e.g. let's assume a hummingbird's wing goes from the fully up position to the fully down position in 1/8 of a second and you want to record the wing in 4 positions - up, 1st quarter, 2nd quarter, down. The strobe will need to flash 4 times within that 1/8 of a second so the frequency will need to be set to 1/32 of a second.

In this scene the hummingbird is hovering so the torso is stationary but the wings are moving. This results in the torso (and anything else not moving in this scene) getting 4 flashes in one position and the wings getting 4 flashes but in four different positions. Flashing the torso 4 times at 1/128 power (equivalent to 1 flash of 1/32 power) gives us a proper exposure at f8. The wings are only going to get hit once though at 1/128 power in each position so they will be under exposed. Our shutter speed must be set to at least 1/8 of a second or slower to catch all the flashes. As we've settled on our aperture and flash power settings the shutter is our last way of controlling the ambient light exposure. The ambient must be sufficiently low for the wings not to disappear against the background and the darker the background the better the ghosted wings will look. Which is why most of this stuff is shot in a dark studio against black. In a dark studio the ambient isn't significant so bulb is convenient if firing your strobes and camera independently.

Settings would read
Flash: 1/128__4--__32Hz
Camera: f8, 1/8sec or slower depending on ambient
Photographer: tanked up with Red Bull and a very twitchy trigger finger

This is the simplest approach though and if you can control all your lighting (or it's within workable limits) you could have any combination of strobe and continuous lighting. Think a scene full of different athletes doing their thing some being strobed and some being lit continuously and blurred.