Off camera flash sync/shutter speed

It seems to me when I mount my 430ex on a receiver, my shutter speed can't go any faster than 1/250 of a second, if I do that I can see my shutter closing and creating a big patch of darkness on my photo. However fill flash works fine when I mLunt the flash on my camera, I can go any shutter speed I want.

Is it my trigger's problem or that's just how it is?

The problem is that you are hitting the camera's synch speed.

The shutter is made of two curtains. There is one covering the sensor, and another one up out of the way. When you take a photo, the first curtain moves out of the way to expose the sensor. Then, the second curtain drops in to cover the sensor again. The time that the second curtain waits is the actual shutterspeed. So if you shoot at 1/250, then the second curtain drops down 1/250 second after the first curtain does. In order for a flash to work, it needs to fire at a point where the entire sensor is exposed. it does this as soon as the first curtain is out of the way.

But the curtain only move so fast. And if you take a photo at a shutter speed faster that 1/250, the second curtain is starting to close before the first curtain has dropped all the way off the sensor. So, when the flash fires at the moment the first curtain is out of the way, the second curtain has already started to close. That means that the second curtain is stopping the light from the flash from reaching a part of the sensor. Only the ambient light (from before the flash fires) is registered by this part of the sensor. This is why you are getting the black bars - the ambient light isn't bright enough to produce an actual image, so it looks tremendously underexposed.

The reason why you can use any shutter speed when you have the flash on camera is because Canon flashes have a function called FP mode. It stands for Focal Plane (no idea why). What this mode does is pulse the flash several times instead of using just one big flash. That way it manages to cover the entire sensor, even though it is never completely exposed all at once. It's basically filling in the black bars with a second flash. The downside to this is that you lose a bit of flash power. This mode is what's letting you get the faster shutter speeds. Have a look at the screen on your flash. I bet in the top center you have a lightning bolt with an H next to it. That's the FP mode, or high speed synch.

When you have your flash mounted on a radio receiver, the flash is only getting the signal "Fire now!" when the first curtain is completely out of the way. it doesn't know that the second curtain has already covered part of the sensor.

Unfortunately, that's how it is. You can use the wireless system built into Canon's flashs to enable FP mode with an off camera flash. You'll need to buy a master unit for the camera. I recommend a 580EX. You might be able to get a second hand mark 1 for pretty cheap. Look on ebay.

^
what he said.

Does the 430 ex have high speed sync mode? If it does, you can shoot higher than sync speed, but I dont' know the specs on that flash.

suecassidy wrote in post #12469335
Does the 430 ex have high speed sync mode? If it does, you can shoot higher than sync speed, but I dont' know the specs on that flash.

Only if the flash is mounted in the hot shoe, being controlled off camera with a Canon master flash or the newest Pocket Wizards. HSS does not work with most wireless triggers.

time to read the flash manual.

Tiberius47 wrote in post #12468156
You can use the wireless system built into Canon's flashs to enable FP mode with an off camera flash. You'll need to buy a master unit for the camera. I recommend a 580EX. You might be able to get a second hand mark 1 for pretty cheap. Look on ebay.

does ettl work wirelessly like this also? if so can it also be done with a canon mr-14ex? i knew i could use the ringflash to trigger my 430ex but thought it had to be in manual mode. if i could have used it for ettl im really going to regret that i sold it a couple of weeks ago.

The 580EX can be used to trigger the 430EX wireless ettl but it's infared so range and conditions are limited.

The Outlaw wrote in post #12470211
does ettl work wirelessly like this also? if so can it also be done with a canon mr-14ex? i knew i could use the ringflash to trigger my 430ex but thought it had to be in manual mode. if i could have used it for ettl im really going to regret that i sold it a couple of weeks ago.

Yes, the MR-14EX and the MT-24EX macro lites can both perform as a master in Canon's E-TTL II system.

The ST-E2 also triggers off camera flash wirelessly, as do the pop-up flashes on the 60D, 7D, and T3i. However, these off-camera solutions do not permit high speed sync and are limited to the max flash sync speed (eg. 1/250 sec on the cameras listed above). That is true even when using ETTL, which I do all the time with my 430EX on my 60D. The 430EX will do high speed sync when on camera. However, high speed sync drains the batteries quickly, slows recycle times, and reduces the maximum amount of light the flash can produce. I basically never use high speed sync.

scroller52 wrote in post #12470175
time to read the flash manual.

If you aren't contributing to thread, why waste your time typing?

I like both an explanation and a visual. Even though this a PW ad the first 3 minutes has a great animated explanation. This really helped me out.

http://www.pocketwizar​d.com …wizard_controlt​l_optimiz/

The Outlaw wrote in post #12470211
does ettl work wirelessly like this also? if so can it also be done with a canon mr-14ex? i knew i could use the ringflash to trigger my 430ex but thought it had to be in manual mode. if i could have used it for ettl im really going to regret that i sold it a couple of weeks ago.

The Canon wireless system supports ETTL.

ScullenCrossBones wrote in post #12470335
The 580EX can be used to trigger the 430EX wireless ettl but it's infared so range and conditions are limited.

The 580 as a master uses pulses of visible light, not infrared, to control slaves. The range is also pretty good. I can easily get ten meters with mine, and for portrait light setups that's more than enough.

I think I knew that now that you corrected me. Thanks.

scroller52 wrote in post #12470175
time to read the flash manual.

Yep,, that's the first thing I do when I have a problem or there's something I don't understand about my camera..

Also, in these forums, there are probably dozens of threads like, "Why do I get a black band on the bottom of my photos when using flash", or words to that effect.

The search tab is your friend