[Entropy]

Cool I was curious.

How do people manage doing high speed photography, I seen it done with the K20. Ie capturing a balloon bursting, etc.

In a dark room, ambient does not contribute to the exposure, only the flash.

The flash burst itself is very short, and independent of mechanical shutter speed. Usually for these shots, the basic process is:
1) Darken room as much as possible
2) Open shutter in bulb mode
3) Trigger whatever event you're trying to capture
4) Flash triggers in response to the event. There are multiple ways of doing this, all need extra electronics. Some people use acoustic triggers (flash pops on loud noise), some use optical beam breakers, there are other options.
5) Close shutter

The key here is that in a dark room, there is no ambient exposure even when the shutter is in bulb mode.

Sync speed, as described here, is the fastest shutter speed at which the shutter is fully open for a period of time. (At faster speeds it becomes a "traveling slit"). A strobe popped when a focal plane shutter is in "traveling slit" mode will only illuminate part of the frame. So mechanical sync speed is a limitation when you are trying to balance flash with ambient (usually in bright daylight, for the purposes of the flash overpowering daylight).

High speed sync will take the flash and pop it multiple times rapidly, causing what is effectively a continuous light for the duration of the shutter. This gives even illumination across the frame at high shutter speeds, but once you enter HSS, the general rule for flash exposure being independent of shutter speed no longer holds true.

You can implement "ghetto HSS" by putting an ND filter on your lens. It has the same basic effect. (See above - HSS begins to be affected by shutter speed once you exceed the camera's sync speed. An ND filter filters the flash, but allows you to increase the shutter speed past sync speed.)

These days, unless you need portability, an ND filter + extra-powerful strobe (like the Adorama FP620M monobloc + battery pack) will be cheaper than an HSS-capable flash and allow the same results in most situations.

[Blue]

I've never encountered a problem. It might be nice with Macro photos to be able to stop motion more effectively, but I'm not hurting.

Now if I had access to a leaf shutter lens and was used to a sync speed of 1/1000 or the like then it might be a big deal.

For now I don't see it as a limit to my photography. (My lack of skill is what is limiting me.)

My Sigma EM-140 DG ring flash has a multi flash mode which allows the flash to fire repeatedly as long as the shutter is open. It can fire up to 90 times. The minimum shutter speed is determined by dividing the number of flashes wanted by selected firing frequency. The cameras is operated in M mode and aperture selected. The power level, frequency and number of flashes are selected on the flash. I haven't capitalized on this because the manual has minimal info and I haven't experimented enough.

[Lowell Goudge]

there is one "limitation" pointed out by a previous poster in the forums a while ago.

Pentax only offers trailing curtain sync at 1/90th i.e. 50% of leading curtain sync flash shutter speed.

the reason is simple, the duration of the flash needs to be added to the exposure time for trailing curtain sync, But, others (eg canikon) offer trailing curtain sync at maximum sync speed.

to me this implies their flash duration must be shorter for the same GN. i.e. prighter but shorter.

now 1/90 could be a problem for some situations

[hll]

Hi everyone,
Is there way to use a off camera flash @ HSS mode. I have a k10d and metz 58.
Thanks
Halil

[Digitalis]

I really do not notice the difference with my Pentax and Canon/Nikon gear as others have said above it's less than a stop of difference. However when i'm using longer lenses I do wish that there was that extra half stop or so to the sync speed, when you are hand holding a heavy 300mm f/2.8 lens even with IS on, hand holding can become problematic.

[MPrince]

Most of the time when using flash I shoot at 1/125. I'll drag the shutter if I need/want to include more ambient light.