Flash & Shutter Speed Question

[Gazer]

Hi. I was wondering whether someone might be able to help me with what is likely a fairly simple issue. For some reason, I cannot set my shutter speed faster than 1/250sec while using my onboard flash or my external flash. My camera's custom function flash sync is off. I'm using an EOS 40D and my external flash is the 580EXII. I recently picked-up the flash and I've only begun learning how to use it.

Thank you for any input.

[oldwolf]

That's the max sync speed of the 40D. The only way you'll get a faster shutter speed is if you set the flash to high speed sync and keep it on the camera. If you go off camera with your flash then you'll be limited to 1/250 sec for the max sync speed.

[OsmosisStudios]

oldwolf is correct: the maximum sync speed is 1/250

What happens is that 1/250 is the fastest speed at which the sensor can be exposed to the light at once. The shutter system is comprised of two curtains: one that blocks the sensor when the camera isnt taking a picture and one that comes up to replace it during exposure. When you press the shutter button, the first curtain is raised up and out of the way, exposing the sensor, while the second curtain rises up.

1/250 is the fastest speed at which the two curtains leave the sensor completely exposed . If you were to go higher, you'd end up with black bands on the top and/or bottom of the frame: this is one or both of the curtains blocking the light from the flash.

[Gazer]

Thanks Oldwolf. You say I can get a faster shutter speed by setting my flash to high speed sync and keep it on camera. Two questions: 1) does this mean that if I'm operating my flash off of my camera (ie: on it's own tripod with a cable remote), I cannot set my shutter speed higher than 1/250th?; and 2) if I leave the flash physically attached to my hotshoe, is there a maximum shutter speed I can use?

Thanks again.

[Digidave]

Originally Posted by Gazer

Thanks Oldwolf. You say I can get a faster shutter speed by setting my flash to high speed sync and keep it on camera. Two questions: 1) does this mean that if I'm operating my flash off of my camera (ie: on it's own tripod with a cable remote), I cannot set my shutter speed higher than 1/250th?; and 2) if I leave the flash physically attached to my hotshoe, is there a maximum shutter speed I can use?

Thanks again.

Actually, you set your camera to high sync speed. I tried a little experiment with my Nikon D80 & the SB800 speedlight attached one day. I've seen pictures with a black bar running across the bottom or top of the photo & people asking what happened. The answer was almost always that they went beyond their sync speed. So I tried it, being the curious sort that I am. I took a self portrait in the shade of a tree & wanted to see if I could get better exposure of the background. I don't remember how many shots I actually took but it was quite a few. Just kept speeding up the shutter speed. I got all the way to 1/4000th of a sec.. That's the fastest a D 80 will go. Result was a bunch of pictures that looked exactly the same. Never did get the black bar across the bottom or top. All exposures were exactly the same. I'm sure there is a mathematical reason for it that would be way to technical to get into here. Keep in mind that I was taking a photo of a static subject. I don't know what the results would be with a moving subject. Would it cut down on ghosting? Try experimenting.

[i speak in math]

Originally Posted by Digidave

Actually, you set your camera to high sync speed. I tried a little experiment with my Nikon D80 & the SB800 speedlight attached one day. I've seen pictures with a black bar running across the bottom or top of the photo & people asking what happened. The answer was almost always that they went beyond their sync speed. So I tried it, being the curious sort that I am. I took a self portrait in the shade of a tree & wanted to see if I could get better exposure of the background. I don't remember how many shots I actually took but it was quite a few. Just kept speeding up the shutter speed. I got all the way to 1/4000th of a sec.. That's the fastest a D 80 will go. Result was a bunch of pictures that looked exactly the same. Never did get the black bar across the bottom or top. All exposures were exactly the same. I'm sure there is a mathematical reason for it that would be way to technical to get into here. Keep in mind that I was taking a photo of a static subject. I don't know what the results would be with a moving subject. Would it cut down on ghosting? Try experimenting.

The Nikon D40, D50, D70 and D80 have a hybrid mechanical/electric shutter that allows a mechanical shutter sync speed of 1/200 but switches to an electrical sync at speeds above that. Most camera do not for good reasons. That is why you didn't get any trailing curtains in you shot; it wasn't using the curtains at all. Normally, you set the camera and speedlight to HHS and the speedlight will flash pulses very quickly while the shutter curtain slides across the sensor resulting a what appears to be a continuous exposure of light.

[oldwolf]

Originally Posted by Gazer

Thanks Oldwolf. You say I can get a faster shutter speed by setting my flash to high speed sync and keep it on camera. Two questions: 1) does this mean that if I'm operating my flash off of my camera (ie: on it's own tripod with a cable remote), I cannot set my shutter speed higher than 1/250th?; and 2) if I leave the flash physically attached to my hotshoe, is there a maximum shutter speed I can use?

Thanks again.

1) You can set your shutter speed to whatever you want to. Whether you get a nice picture without a black bar across it is another matter hehe.

2) Not sure on the max shutter speed. Never really tried it out. Sorry. It should tell you in your manual that came with the flash.

[Gazer]

Thanks everyone. I appreciate your input.