canon's ettl

<p>hello everyone,<br>

i got 6 sunpak's rd2000... i planned to make diy ringflash of them and i was thinking about 2 ways of triggering it.<br>

1st option would be to trigger them manually but i have problem with triggering them this way... i got adapters and whether i'm using my el-skyport or connecting adapter to camera it doesn't trigger it...<br>

2nd option would be to connect them to each other and leave them in ettl mode, but i don't know whether would i got my photos overexposed or not...<br>

so i want to ask you guys 2 questions:<br>

1. do you know any way to trigger them manually other than the ones that i mentioned? i even tried to connect them pin to wire and it didn't work...<br>

2. how would canon's metering (ettl) behave if i had 6 flashes sending pre-flash? i just don't want to spend hours on building cord, connecting pin to pin and finding at the end that it gives me way over exposed pictures... i might be wrong but i have a strange feeling that all of the flashes would try to expose subject independently, please correct me if i'm wrong... </p>

<p>i appreciate your time and i hope you can give me some answers</p>

<p>thanks,<br>

greg</p>

<p>2. I doubt you'd be able to use more than one E-TTL unit at once - it needs to communicate electronically with the camera via the contacts in the flash shoe (unless it has master slave remote communications like the Canon flash units - in which case instructions would be detailed in the manual.)</p>

<p>hey Alec,<br>

i would like to connect pins on the hot shoe of the flashes (so the top pin of the 1st flash to top pin of the 2nd flash to the top pin of the 3rd flash and so on through all off units and then the same with the other 4 pins) - i would like to make custom cord to connect the flash units (i can do that myself) and than use the canon's off camera flash cord...<br>

the only thing that i'm afraid is that ettl will freak out and my photos will be over exposed...</p>

<p>I'm about 110% sure that the camera will only communicate with one ETTL flash unit at a time. If you want to use more than one flash you can sync them together but only in manual mode.</p>

<p>That is a kind of pricey ringflash, if you paid $70 a piece-the AlienBees ringflash is only $400. If you're handy with electronics, you may be able to put together your own TTL connection cord, but I don't think TTL is going to work for you, and since the RD2000 is a fully auto flash, you won't be able to put the flashes in manual and do it that way, although if the TTL control contacts aren't activated, they may just fire at full power, and you could adjust your camera accordingly. I do hope you got those flashes for very cheap or free, because I honestly don't think there is a way you will be able to make them work very well.</p>

<p>ETTL requires a one to one connection between the camera and a "Master" flash. Any subsequent flashes would be slaves and would be controlled by the Master. They can be commanded to fire in ratio's to the Master, or in Manual depending on weather they are assigned to group B or group C. However, this command communication can only take place via the pre flash signals that the master sends out. ETTL is a wireless only connection between flashes. </p>

<p>Bottom line, you can't do this. </p>

<p>I like A. Davis' idea of the Alien Bees Ring flash. Or, let us know what you're shooting and how. Maybe someone here has done it before. I never use ring flash, as I am able to get the same results with my studio lights. But maybe you're going mobile, I dont' know.</p>

<p>hey Bob,<br>

i may have misunderstood what the ETTL is but i always thought it's a metering through the lens + info about distance, where TTL would be only metering without distance info...</p>

<p>regarding what you say: <br>

the flash that i bought (actually 6 of them) - Sunpak RD2000 - has no option of working as a slave... it's fully automatic, and as i found you can't even trigger it manually via hot shoe adapter... what i want to do is build my custom cord where all of the flashes will be connected together... then i'm gonna connect that to Canon's off camera flash cord, so it acts as one flash unit in ETTL/TTL mode...</p>

<p>i know about AlienBee's ringflash, i searched through the net looking for something light and ultra portable, so i can take it on location... and everything would be perfect with AB option if i didn't have to bring some heavy power pack with me everywhere that i want to go...</p>

<p>regards,<br>

greg</p>

<p>My instinct is that to get all the RD2000's to work as one TTL flash unit would require cutting them open, taking the TTL unit out of each flash, and then wiring all the flashes to one TTL unit, which you would mount on your hotshoe. That might work-TTL sends out a very brief pre-flash, which is read by the camera, and then it tells the flash how long to fire for (shoe mount flashes modify their power output by decreasing flash duration, not flash power). I suspect, however, that the TTL unit for the RD2000 is specific to the power output of one flash, so if you are using 6, you would need to set your flash compensation to -2.5. This is all speculation, though-I'm merely guessing here, and have never done surgery on flash units. A side note-be careful of the capacitors if you're opening up the flashes.<br>

The AlienBees ring flash is certainly not the most portable-another option may be the <a href="http://www.bhphotovideo.com/c/product/555767-REG/ExpoImaging_RAC170_2_Ray_Flash_Ring_Flash.html">Ray Flash Adapter ($200)</a></p>

<p>hey Andrew,</p>

<p>i'm going to build that cord between tomorrow and after tomorrow, and we'll see whether it works or not... if not i'm going to sell all the 6 units and get AB or Profoto (either of the with battery pack)...<br>

problem with those flash adapters is that they reduce output power of your flash by as much as 2EV, so on sunny day, shooting with sun as a backlight you have to shoot with ISO 400, which i don't like...</p>

<p>anyway when i'm donne i'll let you guys know how it works...</p>

<p>regards,<br>

greg</p>