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DPChallenge Forums >> Photography Discussion >> Using "high-speed sync" on 5D and 420EX
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Showing posts 1 - 6 of 6, (reverse)
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 04/10/2008 07:04:34 PM · #1
So I've never quite understood this. If I'd like to use a shutter speed of 1/500th and use a flash to assist in the lighting I can do this by shooting with the flash set to the H with lightning bolt right? Is there any reason to think the picture will freeze any differently than if I were to simply shoot 1/500th without flash (assuming I could get the same amount of light)? Is there some limit to how short a shutter speed I can use? Could I do it with 1/2000th? What's the limiting factor? How bright my flash can output?

I know it seems like a basic gap in my understand, but hey, what can you do? :)
 04/10/2008 07:10:24 PM · #2
From my understanding the faster the shutter the shorter the effective distance of the flash. I think it's more for fill flash then for freezing action, though I'm sure it can be used that way for studio work.
 04/10/2008 07:34:45 PM · #3
I think you just need to play around with it to find out. I have the Sigma 530 DG Super and can sync all the way down to 1/8000th but i have to be at around f/2.8 depending on distance if i want to use it as the sole lightsource (which it generally is at those shutterspeeds) and at ISO 100. So i'm fairly certain you can do some significant action stopping with the 420, even if it means bumping the ISO...

The way i understand it is that the flash starts firing (a single long burst) before the shutter opens, and continues firing after the shutter has closed. Meaning that yes - the amount of light (watt-seconds or whatever) outputted by the flash plays a significant role, and that yes you will get the same action freeze as with continuous light (minus the obvious positioning of said light).

ETA (in response to Dirt_Diver) The above is only for the high speed synch functionality of a flash btw.

Message edited by author 2008-04-10 19:39:40.
 04/10/2008 07:35:30 PM · #4
Not sure if this will help you but to me it seems what you are trying to do won't work.

Not saying you don't already know about this but it could help.
//www.youtube.com/watch?v=NfKzY4wMixQ&feature=PlayList&p=BC5A73FEA8B7D7D2&index=1
 04/10/2008 08:19:19 PM · #5
Originally posted by DrAchoo:
So I've never quite understood this. If I'd like to use a shutter speed of 1/500th and use a flash to assist in the lighting I can do this by shooting with the flash set to the H with lightning bolt right? Is there any reason to think the picture will freeze any differently than if I were to simply shoot 1/500th without flash (assuming I could get the same amount of light)? Is there some limit to how short a shutter speed I can use? Could I do it with 1/2000th? What's the limiting factor? How bright my flash can output?

I know it seems like a basic gap in my understand, but hey, what can you do? :)


OK, When you fire the flash in a non High Speed mode, when the shutter opens, it opens all the way to expose the entire sensor, and the flash fires one big pulse of light at your subject. When you put the flash in HSS mode and set the shutter to a speed over the regular sync speed, when the shutter opens, it does not open all the way, but the two curtains make a slit that moves across the sensor, exposing it. The flash, instead of firing one large pulse of light, fires many smaller pulses for the entire time, giving the effect of a much longer light pulse that will illuminate the subject for the entire time the slit is moving.
 04/10/2008 08:22:19 PM · #6
High Speed Shutter vs Ordinary Flash Sync
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