DS125 SubStrobe problem?

Hi this is my first post, most of the time I could find the information that I was looking for by doing a search but this time no luck. Here is my problem I have a Canon 300D in an Ikelite case with the eTTL controller and a DS125 strobe and I can’t get the strobe to preflash. I copied the e-mails sent and received form Ikelite. I am still waiting on a reply from my last e-mail to Ikelite it’s only been one day, it’s not like they are ignoring me I’m sure they get very busy I just get a little inpatient (one of my many flaws). So I thought in the meanwhile I might pose the same questions to this group. Here is the back ground.

Thanks

Damon Chango

E-mail to Ikelite:

I have the # 6870.1 housing S/N 7739 with the eTTL controller, #3944.75 DS-125 SubStrobe S/N 5570 and the digital sync cable #4103.51. I have used it on many day dives and it seems to work fine but this last weekend I used on a night dive for the first time and ran into what I consider a serious problem. The camera would not fire the strobe in the darkness, in order for the strobe to fire I had to shine my dive lights on the subject/object and hold the camera a few inches way from it. This made it very difficult to photograph anything but plant life, because all the wildlife would flee while I was trying to shine my lights on them and get the camera in very close. If I was too far away from the subject it would not fire, I figured there was not enough light getting through the lens for the camera to read this is why I needed to get real close. Shouldn't the eTTL controller send out a preflash from the camera to the strobe to get the strobe power needed and adjust accordingly, because there is no preflash coming from the strobe? Please advise me to what I might need to do.

Thanks

Damon Chango

Response from Ikelite:

The camera will send out a pre-flash signal, but only IF the camera is satisfied it has an accurate focus lock. The camera must have enough ambient natural or artificial light to SEE the subject contrast and get a focus lock BEFORE sending out the pre-flash.

I would recommend using the modeling light in the DS-125 to assist the camera in focusing.

Regards,

Response back to Ikelite

Thanks for getting back with me so quickly but I have a few questions. If that is the case with the ambient light needed to fire a preflash why can I disconnect the hotshoe cable (the one that is connected to the eTTL controller) from the camera and in total darkness get a preflash from the internal camera strobe but then connect the hotshoe cable and try it again the DS125 will not fire a preflash. Shouldn’t the DS125 act similar to the camera internal flash, I guess what I am saying is if it preflashes in total darkness with the camera’s strobe why won’t it preflash with the DS125? I then tested the camera in semidarkness and still do not get any preflash form the DS125 but if I disconnect the hotshoe cable the camera will preflash. As for the using the modeling light built into the DS125 I did use it, I also used a Mini C-Lite mounted on the other handle and at times I had to use HK light canon if there was not enough light reflection from the subject to get the strobe to fire. I understand what you are saying the about the camera focus lock but shouldn’t the preflash act similarly whether you are using the internal strobe or the DS125, this is where I am getting confused? I just can’t seem to get the DS125 to fire a preflash no matter what I do.

Thanks

Damon Chango

Hi Damon,

First of all, welcome to wetpixel! I am sure you will get lots of help here.

I see where Ikelite's question comes from, when the camera is outside of the housing, it uses the built in flash for AF assist, but this doesn't happen when the camera is in the housing. Here is a simple test to distinguish between the focus and strobe problem:

Set the camera to manual focus, set the focus in the lens to, for example, 1m. Then put the camera inside the housing and try to take a picture at night (on land, in a dark room maybe). If the camera refuses to take the picture you have a strobe problem. If strobe fires and the camera takes the picture (even if it is out of focus), what is happening is that the camera is not focusing in the dark and that's why it doesn't take pictures in your night dives.

Hi Damon,

I think that was a misunderstanding. Ikelite thought you meant the normal E-TTL preflash. But you are talking of the strobo feature of the internal strobe supporting the autofocus if ambient light is low, right? It is a compromise allowing you to take pictures with the internal strobe in such low light situations at all. The internal strobe only does it because a real AF assist beam feature is missing. External strobes (Canon landguns, 420EX for example) send autofocus assist beams and therefore don't need those strobo flashes. Same with your Ikelite strobe, it's called modeling light. Strobo flashes would be a poor solution, especially underwater.

Julian

Thanks for your responses, I did try the suggestion from Rocha and set it to manual focus in a dark room and see if the strobe will fire and it does. So I take it that I do not have a problem with my strobe, just in my perception on how it should work. I guess what I thought was a preflash was actually the strobo feature in the camera thanks Jolly for pointing that out. I will have to read a lot more on taking pictures while diving at night because it was a frustrating trying to get enough light on the subject to fire the strobe. Again thanks for your help.

Damon

Hi Damon,

The problem apparently is not to get enough light on the subject to fire the strobe, but enough light to make the camera focus properly. The camera will only fire the strobe (and take the picture) when it is in focus, and if it is dark it will not focus. What lens are you using? Some lenses are faster and focus better in low-light situations, especially the ones that have a maximum aperture of f2.8.

Luiz

Hey Luiz,

I only have the lens that came with the camera, what lens would you suggest I get for the use in night diving.

Damon

Hi Damon, since you are not going to do any wide angle scenics at night, I suggest the Canon EFS 60mm f/2.8. It is a fast lens, it will focus faster and better at low light than the kit lens that you have, and it's good for fish portraits and macro photography of small critters. That's mostly what you will encounter at night.

Luiz

Hi Damon, also take a look at this post about aiming lights:

http://wetpixel.com/forums/index.php?showtopic=9650

They may be your solution for focusing during night dives.

Hey Luiz,

Thanks for the info. I am currently shopping for the 60mm EF-S lens best price I could find is around $398. It looks like this will be the next thing I purchase, also thanks for the link about the aiming lights lots of good information.

Thanks Damon