General Flash Questions: Flash Duration / Asymmetrical or Symmetrical

[StealthLude]

Two part question...

After I started looking into more pack / head flash system. I found the notes on Flash Duration being an important factor. If is typical that you PAY more moeny for a system that has a shoter flash duration? I Found two systems that output the same power (1200 watt seconds) and the only difference I can see if the one that has faster flash duration cost more money. (Ive been looking at profoto and Hensel, and Elinchrom lighting systems and Ive noticed two of the same (power) on a lot of packs.

If this typical to see shorter the duration the more expencive the pack?



Next Question is why get an Asymmetrical over a Symmetrical pack?

Which one is typically more expencive? I assume Asymmetrical since it allows for different powers to be set for each light?

[awad]

this isnt an answer to your question at all, but i use normans a lot, and i still prefer my AB because i can just adjust a slider and not have to worry about switches and knobs.

[Wilt]

I do not equate flash duration brevity with cost of unit. Your observation is more related to country of origin of the product, and the relative expense of items from that country!

Symmetrical vs. asymmetrical...if you plug two heads into one pack, the symmetrical makes the output power the same to each head, regardless of output power setting. So a 1000 w-s pack at full power into 2 heads is 500+500; at half power, 250+250, etc. The assymmetric pack allows each channel to be independently controlled, so that a 1000 w-s pack could run at 500+500, 500+250, 500+125, 250+250, 250+125, etc. If the assymmetric pack permitted two heads into a single channel, three heads could be (250+250)+500 or (250+250)+250 or (250+250+125), etc. It is much more flexible and able to shoot portraiture with two or more heads on one pack with independent output control!

[bill boehme]

Maybe the shorter duration flash allows for slightly faster shutter speed. Whether it is useful depends on what the maximum X-sync shutter speed is for your camera.

[Wilt]

Maybe the shorter duration flash allows for slightly faster shutter speed. Whether it is useful depends on what the maximum X-sync shutter speed is for your camera.

The max shutter speed is governed by the fastest that the shutter blades are fully open at the time that the flash goes off! If your shutter is fully open for 1/200 or 1/250, and if you have a veeerrrry sloooowww studio flash, the flash unit would have to have a flash duration of longer (e.g. 1/100) in order for it to be cut off by the closing shutter. The slowest studio units might actually have 1/400 as the Full Power flash duration, but no focal plane shutter cameras have shutters that are fully open at faster speeds! However, with the leaf shutters found on view cameras (or medium format HasselBlad and Bronica and Rollei), leaf shutters can synch at the fastest speeds so cutoff could indeed occur.

[bill boehme]

The max shutter speed is governed by the fastest that the shutter blades are fully open at the time that the flash goes off! .........

It is a little more complicated than that. I did mention X-sync shutter speed in my post. That is the length of time that both curtains are fully open plus the flash duration time plus a worst-case toerance to allow for manufacturing tolerances in timing for both the flash duration and for variation in the curtain timing.

[Wilt]

Bill, what you just wrote I do not dispute. I was merely trying to point out that max shutter speed is not duration of the flash dependent unless the flash output duration is slower than the shutter speed, which is not likely for most focal plane shutter cameras.

a different factor is also the rise time to peak light output, and if the flash is slow on the rise time, that can affect things as well...like the flashbulbs of old caused the need for M synch.

[PacAce]

Maybe the shorter duration flash allows for slightly faster shutter speed. Whether it is useful depends on what the maximum X-sync shutter speed is for your camera.

I understand where you are coming with this from but a longer flash duration doesn't limit you to a slower shutter speed. Whatever the max shutter speed is on the camera is still usable. The only difference is that part of the light from the strobe is wasted because it isn't used to light the image so it's effective power is decreased.

[bill boehme]

I understand where you are coming with this from but a longer flash duration doesn't limit you to a slower shutter speed.......

I did not mean to imply that. My actual thought had to do with short flash duration and its effect on speeds above X-sync where both curtains are in the field of regard (in front of the sensor) at the same time and getting the full benefit of all of the flash energy. I did not mean to create chaos. But, maybe my thought pattern was not in "sync".