Why is x-sync a camera feature?

Can someone explain why the x-sync speed is a camera feature rather than a flash feature? I would assume that the speed at which the flash fires a burst that can be recorded by the camera would be a flash design parameter; in other words, the flash should be the limiting factor for sync, not the camera. If the 1D3 can have an x-sync of 1/500 with a 580ex, why can't the XT?

I think it's because it's entirely dependent on the design and ability of the camera's shutter.

Poe wrote in post #6360559
If the 1D3 can have an x-sync of 1/500 with a 580ex, why can't the XT?

Yeah, and why does a Porsche cost more than a Kia?

Poe wrote in post #6360559
Can someone explain why the x-sync speed is a camera feature rather than a flash feature? I would assume that the speed at which the flash fires a burst that can be recorded by the camera would be a flash design parameter; in other words, the flash should be the limiting factor for sync, not the camera. If the 1D3 can have an x-sync of 1/500 with a 580ex, why can't the XT?

Read this carefully and you will understand the basic concept of a focal plane shutter, the inherent design, and the inherent design limitations.

http://en.wikipedia.or​g/wiki/Focal-plane_shutter

Enjoy! Lon

The sync speed of the camera is not the speed at which the flash fires. It is the maximum shutter speed that will allow the sensor to receive all the light from the flash.

The 1D3 can sync at 1/300s (with an EX speedlight, 1/250s with other flashes/strobes), not 1/500s. It can sync at 1/500s (all the way up to 1/8000s), when you turn HSS on when using an EX series speedlight (and some third party flashes). An XT can make use of HSS as well.

Correction...1Ds3

Titus213 wrote in post #6360722
The sync speed of the camera is not the speed at which the flash fires. It is the maximum shutter speed that will allow the sensor to receive all the light from the flash.

I realize that. But why the different x-sync speeds between cameras?

Gatorboy wrote in post #6360674
Yeah, and why does a Porsche cost more than a Kia?

You could have been more constructive in your reply.

FlashZebra wrote in post #6360721
Read this carefully and you will understand the basic concept of a focal plane shutter, the inherent design, and the inherent design limitations.

http://en.wikipedia.or​g/wiki/Focal-plane_shutter

Enjoy! Lon

Thanks! This explains its. It's more of a design issue of creating a FP shutter that can move extremely fast so as to allow the full sensor to be exposed by flash rather than a moving slit.

Poe wrote in post #6361272
I realize that. But why the different x-sync speeds between cameras?

For the same reason some shutters are rated at higher actuations I would think - material and design. The higher end cameras have better material and design? Shooting film for years I had 1/60 and then it jumped to 1/125 and it was a big deal. Now at 1/250 (20D) it's really good. And with high speed sync to my cameras max of 1/8000 I'm happy.

Poe wrote in post #6361268
Correction...1Ds3

The 1ds3 only syncs at 1/250s. You are probably thinking about the original 1D, which is spec'd to sync at 1/500, but actually can technically sync at any speed, due to the fact that it uses an "electronic shutter" instead of a conventional shutter. Since there is no actual physical shutter in it, there is no shutter to "creep" into the image, thus the sync speed is not mechanically limited.

DDCSD wrote in post #6361370
The 1ds3 only syncs at 1/250s. You are probably thinking about the original 1D, which is spec'd to sync at 1/500, but actually can technically sync at any speed, due to the fact that it uses an "electronic shutter" instead of a conventional shutter. Since there is no actual physical shutter in it, there is no shutter to "creep" into the image, thus the sync speed is not mechanically limited.

Ooooh...I mixed up a different shutter speed I saw on the specs with the x-sync for the 1D3. The x-sync is 1/250 I see upon review.

Roughly speaking, the flash itself is instantaneous (typical electronic flash durations are 1/1000 to as short as 1/100,000 second).

Because the flash is so brief, it illuminates only the part of the sensor that is exposed to light at the moment it fires. The shutter must open fully, exposing the entire sensor; then the flash must fire before the shutter starts to close.

Focal-plane shutters get their higher speeds by moving a slit across the sensor. Above the X_sync speed, there is a never a time when the entire sensor is exposed.

Some flashes have a "high-speed sync" mode in which the flash fires several times as the slit moves, so that you wind up with even flashes across the sense. This feature isn't normally very useful, though.

Turning for a moment to history, old bulb flashes for one-time use took a long time from when they were fired (literally, ignited) until maximum light output. To keep up with Curtis N's famous maxim of having the flash go off while the shutter is open, they actually had to fire the flash before the shutter started moving. You'd have perhaps 1/10 of a second in which the flash reached full output, followed by a 1/60 exposure with essentially constant flash output. Then you'd thrown the bulb away with no concern for the fact that it was toxic waste.

DDCSD wrote in post #6361370
Since there is no actual physical shutter in it,

There is, but it doesn't do much more then "protect the sensor from dust"... Fastest speed it does is 1/125 or 1/250s or so... Faster speeds are done by switching the CCD on and off like you say.