| Sign in: |
| Members log in here with your user name and password to access the your admin page and other special features. |
|
|
|
|
|| SportsShooter.com: Member Message Board
Quad Head/Watt Seconds/Flash Duration?
Jon Blacker, Photographer
 |
Toronto | ON | Canada | Posted: 7:13 PM on 04.05.09 |
->> I'm fairly certain I have this right, but do acknowledge that sometimes I don't even know enough to know that I don't know...
I have a pair of Speedotron 104 2-cable quad heads. (The difference between the 104 and the 105 head is that the 104 can handle 1200ws per tube while the 105 can handle 2400ws per tube). My question is this;
Following the bouncing ball of logic, would it be reasonable to figure that with all four cables of these two heads, plugged into a single 2400ws pack set to combine all channels, that I would end up with 300ws per tube? If yes, what would my flash duration reasonably be best guestimated to be against the 105?
According to the Speedotron site, the 105 head delineates flash duration in part like this:
2400ws = 1/1175sec flash duration
1200ws = 1/2000sec flash duration
Relative to a single tube 102 head for reference:
2400ws = 1/225sec flash duration
1200ws = 1/400sec flash duration
Would it be unreasonable to think that the flash durations of the 104 would be close to the that of the 105? It's my intention to use these heads to stop motion during an upcoming portrait session where the subject will be jumping.
Thanks for your thoughts... |
|
Shawn Cullen, Assistant
|
San Diego | CA | | Posted: 1:16 AM on 04.06.09 |
->> Jon,
I am pretty sure you have it all right, 300ws per tube. However, the one feature that these heads have is if one of the tubes goes out for some reason, it will transfer the power, or double it, to another tube. So if one of the tubes is bad, you will have 6 tubes getting 300ws and 1 getting 600ws.
With 2 heads and all four cables plugged into one 2400ws pack, and both the 800 and 400 sides are combined, you will get 1/2000sec of flash duration out of each head.
I would think that the 104 series head and the 105 series head would be comparable in flash duration. The only differences that I can think of, is if the cable length is longer on one head versus another. Longer cable length will decrease flash duration and power. This amount is dependent on how much longer the cables on one head are.
For the record, I have never used the 104 heads, only the 105 heads. |
|
Jon Blacker, Photographer
|
Toronto | ON | Canada | Posted: 9:47 AM on 04.06.09 |
->> That's great Shawn. Thanks very much.
I was aware that the power from a failed tube would transfer to the second tube in that pairing, however these heads have new tubes so that shouldn't come into play. If it does, I have a spare.
These heads have the factory-standard 20-foot cables. That is what the 105 flash durations in the Speedotron chart are calculated with, so I should be okay there too.
I will be testing ahead of time, but it's good to know that it would appear that this is going to work the way I had hoped. This confirmation is a great starting point.
Thanks again. |
|
Robert Seale, Photographer
|
Houston | TX | USA | Posted: 11:30 AM on 04.06.09 |
| ->> I think that may be a typo....longer cable length usually increases flash duration. |
|
Shawn Cullen, Assistant
|
San Diego | CA | | Posted: 1:32 PM on 04.06.09 |
->> Robert,
Your are correct, my mistake! It would increase the flash duration!
For some reason when talking about flash duration I always seem to get the terminology mixed up to describe lengthening or shortening the flash duration. Thanks for pointing that out! |
|
Jon Blacker, Photographer
|
Toronto | ON | Canada | Posted: 2:01 PM on 04.06.09 |
->> For good or evil (remember, sometimes I don't even know enough to know I don't know), I knew what Shawn meant relating cable length to flash duration, though it reads backwards in his post above; longer=longer, shorter=shorter.
Thanks for pointing it out Robert. |
|
Return to --> Message Board Main Index
|