shutter wont go above 200 with flash attached

[DeepSpring]

I have a sigma 500 st flash on my rebel xt. When the flash is mounted In manual mode Av and Tv the flash won't go above 200 and I can not understand why. is there something in the camera I can change?

 

[darin3200]

That's the flash sync speed. You can probably find some stuff on good about it. Basically it becomes hard to coordinate the shutter firing and the flash of light. It also becomes a problem with subjects different distances away because some of the light won't get back in time.

So the camera 'protects' you from doing that. Sometime try shooting in manual with a 1/500, 1/1000 and 1/2000 shutter and you'll see why

 

[W.Smith]

But a flash's duration is measured in thousandths of a second. So if you're trying to take a flash photo of a rallye car careening past you at 60mph, you'll 'stop it cold'!*
Your flash's duration has effectively become your camera's shutter speed.

*if the camera/flash combo didn't move!

 

[tempra]

The shutter takes 1/200th of a second to operate, however it isn't fully open for all of that time.

When the shutter is released, a gap the size of the sensor slides across the sensor, so there is only a fraction of a second that it is fully open (less than 1/200th) and if your flash fires at a 1/1700th, if it fires too early or too late, the moving shutter will cut off the light from that part of the frame.

So, if your shutter is fully open for 1/1500th at 1/200 shutter speed (arbitrary number, but the maths are possible) and your flash fires at 1/1700 then you have a tiny amount of leeway to get all of the light into the frame, hence why the sync speed is set to that.

I think. :mrgreen:

 

[DeepSpring]

Ok thanks guys I got it. At first I was freaking out somehting was wrong with my camera or something like that. Now as I was hoping to use the flash for outdoors fill flash as well as the low light stuff it's time to invest in a neutral density filter.

 

[W.Smith]

Ok thanks guys I got it. At first I was freaking out somehting was wrong with my camera or something like that. Now as I was hoping to use the flash for outdoors fill flash as well as the low light stuff it's time to invest in a neutral density filter.

You could also dial down the output of your flash to 1/2, 1/4, or even 1/8 of full power. And/or use a [ame="http://www.youtube.com/watch?v=RNCmuExlHvM"]bounce card[/ame].
Plus its cheaper and quicker than ND filters.