Does flash limit shutter speed?

joshhuntnm

I was taking some Sr. Pics today and using the flash to fill shadows. Unless I am mistaken, the flash being on seemed to not allow the shutter to go above. . . I think 200. is this right?

I have a canon xti and was shooting in AP.

DoctorIt

joshhuntnm wrote:

I was taking some Sr. Pics today and using the flash to fill shadows. Unless I am mistaken, the flash being on seemed to not allow the shutter to go above. . . I think 200. is this right?

I have a canon xti and was shooting in AP.

Yes, the flash sync speed is limited on all cameras. Pro bodies will typically give you a slightly higher sync, maybe 1/500. I think my D2h used to give me 1/250


HOWEVER, you'll find that the "true" exposure time will be much less than 1/200th since it is being dictated by the fire duration of the flash. In other words, the shutter may be open for 1/200 of a second, but the flash will only fire for approximately 1/1000th of a second. So in a dark setting, with flash as your primary light source, your "effective" exposure is more like 1/1000th.

For example: if you look at the exif on the following photo, you'll see its 1/15s - there's no way you can freeze a water droplet crown and satellite drops with that long of an exposure. What the exif doesn't say is that I shot that in a fairly dark kitchen with my flash set at 1/8 power (which means an even shorter flash duration) giving me an effective exposure of something like 1/3000s.

joshhuntnm

Thanks. I had read about flash sync but never understood it.

I read somewhere about a second flash curtain, but never understood that either. I don't guess that will help me.

What I am wanting to do is use the flash as a fill in fairly bright light, and keep the apeture open pretty wide.

cool pic by the way. I am thinking it took a few tries to get that one!

Richard

joshhuntnm wrote:

Thanks. I had read about flash sync but never understood it.

I read somewhere about a second flash curtain, but never understood that either. I don't guess that will help me.

What I am wanting to do is use the flash as a fill in fairly bright light, and keep the apeture open pretty wide.

cool pic by the way. I am thinking it took a few tries to get that one!

To combine bright light, wide aperture and flash, you need to put the flash in high speed synch mode. Don't know what flash you are using, but many have this feature.

joshhuntnm

Richard wrote:

To combine bright light, wide aperture and flash, you need to put the flash in high speed synch mode. Don't know what flash you are using, but many have this feature.

I use a canon 580. I will look that up. thanks.

Richard

joshhuntnm wrote:

I use a canon 580. I will look that up. thanks.

Great...the 580 has a button on it to switch into high-synch mode.

pyry

joshhuntnm wrote:

Thanks. I had read about flash sync but never understood it.

I read somewhere about a second flash curtain, but never understood that either. I don't guess that will help me.

There's basically two shutters in an slr. When the shutter is closed and ready to take a frame the first curtain covers the sensor (or film) and second is open. When you take a shot, things start happening:

1. shutter button is pressed, mirror moves up and the lens aperture stops down.

2. The first curtain begins to move across the frame.
3. After exactly the selected shutter speed the second curtain starts across the frame to close the shutter. With very short shutter speeds the first curtain is still moving when the second curtain begins to chase it down.

4. The shutter closes fully, the image is recorded, curtains move back to square one, mirror flips down and lens aperture opens up. A small gnome living inside the camera resets his crank and yells "Next!"

Co-operation of a flash can be accomplished by firing either when the first curtain has fully opened or just before the second curtain begins to close, the latter is called second curtain sync.

The fastest shutter speed at which the first curtain makes it all the way open with just enough time to spare for firing the flash, before the shutter starts to close, is the cross-sync (it's also the point at which the first and second curtain syncs become the same thing). This is determined by how fast the little gnome can make the curtains move.

High-speed sync gets past that limit by firing the flash continously at a very high rate (we're talking more than 20000 little flashes per second). This way, the flash is turned on first, then the curtains move, and finally the flash turns off. The result is that the shutter curtains do not need to open fully for the flash to illuminate all of the frame. There's penalty in the form of less light available from the flash.

Hope this helps!

pathfinder

Josh, there is a lot of information about the EOS and non-EOS flash systems at the top of the Finishing Forum in the stickies.

When shooting out of doors in bright light with fill flash, I leave my flash in High Speed Synch routinely. As mentioned there is a slight penalty in light loss, due to the continous vs single flash mode of HSS, but the 580 handles that with aplomb.

Without High Speed Synch, the camera is unable to go higher than 1/200th of 1/250th ( EOS cameras ) and it is easy to not notice this as there is no big alert when shooting in Av mode or Manual Mode.. And then your pictures are over exposed.


I prefer to shoot with the 580ex in ETTL in Manual Mode with HSS enabled. Second curtain shutter is useful when shooting in dark environments for that blurred, streaking sort of image. Some pros leave 2nd curtain always enabled - little downside to doing this.

jeffreaux2

I agree with everything Pathfinder said.

I Mainly shoot in AV mode and use the 580 in High Speed Synch mode and in Auto ETTL. It works fine. Then it is just a matter of thumbing the flash exposure compensation wheel to adjust the amount of light you are throwing. 2nd curtain synch would be useful especially for panning type shots where you are trying to use a slower shutter speed to capture some movement before ...."flash"....freezing your subject in the frame. When outdoors, I ALWAYS set the flash to HSS mode. There is nothing to be lost by doing this, and very much to gain.....especially when using large apertures for portrait work.

pathfinder

One of the appeals for the G9 point and shoot, besides RAW and nice image quality, is the ability to use the EOS flash system.

There was a blog recently on the Strobist where he says he can get the G9 to synch with a manual flash at 1/2500th of a sec - but he did not describe exactly what he did to achieve synching at this high a speed. Should be an interesting follow on article I suspect.

Why would you want to synch with a shutter speed of 1/2500th, you ask? It allows you to shoot out of doors in full sunlight, and have the sun lit portion of the image be 3 full stops darker than the flash illuminated portion of this image - powerful stuff!! Cool! The 580ex and the Vivitar 285HV both have plenty of power to override full sunlight out of doors if used properly. But they do not normally allow you to drive sunlit areas 3 stops further into the darkness, with most standard DSLRs. The Nikon D70 does synch at 1/500th.

pyry

pathfinder wrote:

One of the appeals for the G9 point and shoot, besides RAW and nice image quality, is the ability to use the EOS flash system.

There was a blog recently on the Strobist where he says he can get the G9 to synch with a manual flash at 1/2500th of a sec - but he did not describe exactly what he did to achieve synching at this high a speed. Should be an interesting follow on article I suspect.

Why would you want to synch with a shutter speed of 1/2500th, you ask? It allows you to shoot out of doors in full sunlight, and have the sun lit portion of the image be 3 full stops darker than the flash illuminated portion of this image - powerful stuff!! Cool!

That is a creative idea right there

Super-high x-syncs can't actually utilize full power from the flash, because the pop would be longer than the exposure. So, I'm thinking, you could get the same or even more extreme results with a normal slr and an nd-filter.

ziggy53

pathfinder wrote:

...

There was a blog recently on the Strobist where he says he can get the G9 to synch with a manual flash at 1/2500th of a sec - but he did not describe exactly what he did to achieve synching at this high a speed. ...

Many P&S and advanced digicams don't have sophisticated mechanical shutters. Instead they use a simple shutter (more like a cover) for the imager and then the imager itself has an electronic shutter which is really just how the imager is activated.

I used to regularly use both the Sony F828 and Minolta A2 digicams with electronic flash at 1/2000th. Nothing special required, just a flash with simple sync and manual controls will do.

ziggy53

pyry wrote:

That is a creative idea right there

Super-high x-syncs can't actually utilize full power from the flash, because the pop would be longer than the exposure. So, I'm thinking, you could get the same or even more extreme results with a normal slr and an nd-filter.

Just remember that the ND filter will attenuate both the ambient light and the flash. You won't get much reach if you add too much ND filtration.

The effects of ND filters and FP/HSS mode are similar except with FP/HSS mode autofocus and viewfinder brightness are much better.

pathfinder

pyry wrote:

That is a creative idea right there

Super-high x-syncs can't actually utilize full power from the flash, because the pop would be longer than the exposure. So, I'm thinking, you could get the same or even more extreme results with a normal slr and an nd-filter.

I doubt you will find a portable flash that will over drive sunlight by three stops while sporting an ND filter on your lens. I could be wrong I s'pose.

An ND filter decreases flash and ambient light, while HSS does not diminish ambient light but allow shutter speeds much higher than standard synch of most focal plane shutters at 1/200th or so.

pyry

pathfinder wrote:

I doubt you will find a portable flash that will over drive sunlight by three stops while sporting an ND filter on your lens. I could be wrong I s'pose.

An ND filter decreases flash and ambient light, while HSS does not diminish ambient light but allow shutter speeds much higher than standard synch of most focal plane shutters at 1/200th or so.

You might find the very same flashes that will give you the 3 stops at higher than usual x-sync. Because you cannot fit a full pop into 1/2500 s. So I'm thinking it's worth a shot.

pathfinder

David Hobbe seems to think you can.....