Paul C. Buff, Inc. Technical Forum

I am trying to understand the t1 flash duration with the Zeus Bi-Tube head using the 2500 watt/second (Ws) power packs. This would also include using dual 2500 power packs on a single head to realize a potential 5000 Ws.

From the Zeus Bi-Tube head product page:
1/350 second at 5000 Ws (connected to two Z2500 packs)
1/600 second at 2500 Ws (connected to one Z2500 pack)
1/900 seconds at 1250 Ws (connected to one Z2500 pack)

Questions:

#1. Why does the flash duration get longer when two packs are used? The two tubes in a Bi-Tube head seem to be on separate circuits so I'd expect the flash duration to remain the same.

#2. How do I get the 1250 Ws and 1/900 second duration from a 2500 pack? In other words, what configuration or settings on the 2500 pack achieve 1250 Ws?

Thank you in advance.

for Q1- When both leads are connected to the same pack, but different sockets, 1250Ws goes through tube A, and 1250Ws go through tube B. When each lead is connected to separate packs, 2500Ws go through A and 2500Ws go through B. The more energy that goes through a tube (at a given voltage) the longer the flash takes to burn. In this scenario, you are doubling the amount of power through each tube. If you connect one lead to the pack, then all 2500Ws go through one tube, and that duration would be the same as with two packs.

Similarly, one head connected to A sockets on two packs each set to 3/4 will be faster than if set to full (albeit at a lower power). Both heads connected to B sockets set to 1/4 will be faster still.

For Q-2- It appears this is a typographical error. 1/900s is the t.1 duration is with both leads connected to one Z1250 pack set to full. I apologize for any confusion, and I will bring this up for correction.

OK, thank you for the prompt reply. You indeed answered my questions.

If I change the ratio switch on the 2500 power pack can I get shorter t1 flash durations? If so, then what are the t1 times?

If you have one head with both leads connected to one pack, changing the distribution will not decrease your flash duration. In fact it would increase it, as you would be sending more power through one tube, so one tube's duration would get longer while the other got shorter.

As stated above, if you connect one lead to socket A of one pack, and the other lead to socket A of another pack, and both packs are set to 3/4 power (3750 total Ws), then you will have a faster flash duration than you would at 5000Ws. Similarly, each lead connected to the B sockets of two packs (1250Ws) it would be faster still (as fast as one bi tube head connected to two sockets of a Z1250 pack, or ).

I do not have the spec readily available for the 3750Ws scenario, but you can figure it is between the 1/350 of a 5000Ws set up and the 1/600 of a 2500Ws set up. I will work on getting a better figure for you.

Again, we do not have an exact spec, but in reviewing the data at hand, you can expect about a 1/450 to 1/475 t.1 at 3750Ws.