Canon Speedlite 580EX II and High speed sync

[Dockland]

Ive just ordered a Canon Speedlite 580EX II to my 40D and have read a little about High speed sync on flash. How does that work?
Can I take a picture @ 1/8000 and still get flash sync? I thought it was lockt to max 1/250? Can someone explain the benefits and pros and cons.

Thanks

Tim

[cdifoto]

You can shoot at 1/8000th but you'll have virtually NO range left, so you'll probably never do that. There's not much reason to anyway.

[twofruitz]

There is a mode with a H next to the flash symbol which fires the flash during the shutter release. I am not sure about the workings of it, but I used flash for tennis photos last week at about 1/2000 and they seemed to be evenly lit.

[NewattheGame]

By selecting the high speed synch setting, the flash will synch at any shutter speed but its range will fall away dramatically as shutter speed increases. Below 250 the flash pulses between shutter opening and closing (or when the leading blade opens and before the traling blade closes). Above 250 the shutter is already closing before the full flash output is delivered, this limits its range? More knowledgable people can verify?

[Dockland]

This seems to be a nice feture. Ive looked at photos on this forum, a lot of portraits is awesome with settings around 1/8000 high speed sync in fill flash enviroment. That was the main reason that I decided to buy this external flash.

[SkipD]

Originally Posted by Dockland

Ive just ordered a Canon Speedlite 580EX II to my 40D and have read a little about High speed sync on flash. How does that work?
Can I take a picture @ 1/8000 and still get flash sync? I thought it was lockt to max 1/250? Can someone explain the benefits and pros and cons.

For you to understand "high speed sync", you first need to understand the concept of the focal plane shutter and the "max sync speed". At the end of this explanation I get back to the "high speed sync" thing.

Focal plane shutters (common on SLR cameras) consist of two "curtains", usually made of rubberized cloth (in old film cameras) or very thin metal. The first curtain (which I will call the "leading" curtain) normally covers the film or sensor, hiding it from the light coming through the lens. When you take a photo, the leading curtain moves across the film/sensor to expose it to the light. After the leading curtain has moved, another curtain (which I will call the "trailing" curtain) starts to move, again covering the film/sensor to hide the light from it.

At shutter speeds below the "Max Sync Speed", the leading curtain travels all the way across the film/sensor, fully opening the film/sensor to the light, before the trailing curtain starts to move. At higher shutter speeds, the trailing curtain starts to move before the leading curtain has completely travelled across the film/sensor. What happens to create the very fast "shutter speeds" is that an open slot between the two curtains travels across the film/sensor.

While old focal plane shutters (like in my Nikon F cameras from the 1960's) travelled horizontally, the shutters in most modern SLR's travel across the short distance of the film/sensor frame. The concept of "curtains" turns into one of "blades", but the travel concept is still the same. The leading blade moves first, uncovering the film/sensor, and the trailing blade follows, covering up the film/sensor.

The advantage of the blade style of focal plane shutter is that it can move across the whole film/sensor area faster than the old style curtains. Thus, the maximum sync speed is higher than in the old cameras (max 1/60 for my old Nikon F's, and 1/250 for the 20D).

The concept of a maximum sync speed, however, still applies. If you try to use a flash at higher shutter speeds (faster than the shutter speed at which the leading curtain/blade is fully open before the trailing curtain/blade starts to move), part of the film/sensor will be covered by one or the other of the curtains/blades when the flash (with a very short duration) goes off. Part of the film/sensor will not "see" the light from the flash, and that part of the image will be either black or very dark.

In the "high speed sync" mode, Speedlites emit a series of very short pulses of light for a long enough period to emulate a constant light source while the focal plane shutter moves across the film/sensor. The power output of the Speedlite is very low during the "high speed sync" operation because if it was putting out high power pulses it could not recycle fast enough.

The only use for "high speed sync" that makes any sense to me is for using the flash as a fill in an otherwise very brightly lit situation.

[martinsmith]

Great flash....bit pricey. I've not regretted buying mine, but the bargain was my 2nd hand Noink unit.

[Dockland]

Thank you all and special thanks to SkipD for exellent explanation.

[Inspired Photography]

Awesome post Skip, nice one.

As others have said... try and avoid High Speed Sync unless you really need it.

Rob

[sfaust]

While I also recommend to avoid high speed sync anytime you need more than a fill effect, I highly recommend to use high speed sync for fill flash effects when you also want to use wider aptertures to soften the background. It works perfectly in that scenario.

[René Damkot]

Originally Posted by cdifoto

You can shoot at 1/8000th but you'll have virtually NO range left, so you'll probably never do that. There's not much reason to anyway.

That's a bit exagerated...

[A.S.I.G.N. Observatory]

I have been turning on the high speed sync on the back of my 580EXII with the little lightning bolt H button on the rear. The same lightning bolt and little H appears on the 580 display. I've tried shutter speeds faster than 1/200th of a second on my 5D MK II.

There is STILL a black portion of the photo.

WHY?

[AntonLargiader]

Possibly there's a contact problem between the flash and the hotshoe? Your actions seem correct. In fact, I don't think there's anything you can actually do to create banding with a properly functioning camera and Canon ETTL flash. The camera just won't allow it; the shutter speed will drop automatically to sync speed. At least, it does on my T2i.

I'm thinking that the camera doesn't know the flash is there, because otherwise it would either limit itself to 1/250 or else tell the flash when to fire in order to expose the whole frame. Sounds like the flash is firing from the center hotshoe pin, and not via the stuff that communicates things like HSS and 2nd curtain sync.

[John Sheehy]

Originally Posted by Dockland

Ive just ordered a Canon Speedlite 580EX II to my 40D and have read a little about High speed sync on flash. How does that work?
Can I take a picture @ 1/8000 and still get flash sync? I thought it was lockt to max 1/250? Can someone explain the benefits and pros and cons.

Basically, it is just a fast-flashing strobe light during the period of exposure. Rather than waiting for both shutter curtains to be open and then making one short blast, it pulse the entire time from when the first curtain starts to move, until the sensor is covered again.

It is nothing more than extra light, as it does not stop action at all; only your shutter speed does. If something is moving very fast lengthwise in the frame, it will skew, just like with ambient light at high shutter speeds.

The guide number decreases tremendously as you increase the shutter speed. At 1/8000, you will only see much of a flash influence at high ISOs, wide apertures, and/or close subject distances.

[A.S.I.G.N. Observatory]

Originally Posted by AntonLargiader

Possibly there's a contact problem between the flash and the hotshoe? Your actions seem correct. In fact, I don't think there's anything you can actually do to create banding with a properly functioning camera and Canon ETTL flash. The camera just won't allow it; the shutter speed will drop automatically to sync speed. At least, it does on my T2i.

I'm thinking that the camera doesn't know the flash is there, because otherwise it would either limit itself to 1/250 or else tell the flash when to fire in order to expose the whole frame. Sounds like the flash is firing from the center hotshoe pin, and not via the stuff that communicates things like HSS and 2nd curtain sync.

That was it exactly!!! I took the flash off the hotshoe, put it back on, secured it and gave it a bit of a wiggle. Now it works. Thanks heaps mate!

Just took a photo at 1/320 sec and NO banding! Awesome sauce.

Baz.