Ikelite housng for Canon EOS 40D and DS 125

Hi,

I bought last year the Ikelite housing for a Canon EOS 40D with a DS 125. Unfortunately I have no many oppotunities to use it, so my confidence level is low. My problem is that the strobe seems to work in TTL mode, but I never get exposure time short enough to get not blurred pictures, working in Av or in Tv. This, of course, especially with a dark scene. In Av I set also the camera to 1/250 in Av or 1/125 in Tv, but also the lowest f-stops are not enogh to get a correct exposure from the camera. The camera fires the strobes but it seems to use the aperture and shutter as it hasn't. The green confidence signal of the strobes usually doesn't glow.

The housing is set to DS 125 and not to DS 51. In the camera I don't get the menu to change the external flash settings.

I use a Canon macro 60mm and a Tokina 10-17mm.

Are there any settings in the camera to choose or do you have any suggestions?

Thanks in advance for your help.

Ettore

Hi etruss,

I'm in no way an expert, but I will tell you what worked for me getting started. Set the camera to "M" - manual. Then, based on subject and lens pick an aperture and shutter speed to set what you think will be the best of each - in terms of how you want the photo to look. Here's an example; I was shooting a small fish with my 100mm macro, so I stopped down the lens aperture to f10 to get the depth of field I wanted (ideally, I wanted the entire head in focus, if possible), then set a fast enough shutter speed to freeze any movement, I figured 1/100th of a second would do it. Then, I set the strobe to TTL and fired away. As long as you're close enough, you should get a usuable image. Here's the image in which I did exactly what I just explained. Oh, and while more experienced shooters may use Tv or Av at times, I've yet to use any mode other than manual.

Hope that helps.

Lee

Shot in manual, f10, 1/100th, DS-160 on TTL

What your doing when your going into Manual and using TTL, is basically letting the flash expose for you. It sort of depends how much ambient light you have in the water, but if its dark enough, it doesn't matter much how low you set the shutter speed, since its going to be the flash that is the dominant light source, and the flash will only last for a very brief period of time (think 1000:th of seconds).

If your in Av or Tv mode, the camera is trying to expose correctly with the ambient light, ignoring the fact that you have a flash attached (it just won't go over the sync-speed you have, so you might end up over exposing). So your camera will think its really dark, slow down the shutterspeed (if in Av mode) or open up the aperture (if in Tv mode) until it exposes correctly, and then the flash will not have to output much light at all when its it turn, since the camera did all the thinking regarding the light before hand.

Now I'm mostly speaking from over water experience, but thats how TTL works, and I guess you'd be using Av and Tv mode in the same way as you do over water, ei as fill flash. But I'd still guess the experienced photographer would use M mode, and then not use TTL but rather use Manual flash too.

/Björn

What your doing when your going into Manual and using TTL, is basically letting the flash expose for you. It sort of depends how much ambient light you have in the water, but if its dark enough, it doesn't matter much how low you set the shutter speed, since its going to be the flash that is the dominant light source, and the flash will only last for a very brief period of time (think 1000:th of seconds).

 

If your in Av or Tv mode, the camera is trying to expose correctly with the ambient light, ignoring the fact that you have a flash attached (it just won't go over the sync-speed you have, so you might end up over exposing). So your camera will think its really dark, slow down the shutterspeed (if in Av mode) or open up the aperture (if in Tv mode) until it exposes correctly, and then the flash will not have to output much light at all when its it turn, since the camera did all the thinking regarding the light before hand.

 

Now I'm mostly speaking from over water experience, but thats how TTL works, and I guess you'd be using Av and Tv mode in the same way as you do over water, ei as fill flash. But I'd still guess the experienced photographer would use M mode, and then not use TTL but rather use Manual flash too.

 

/Björn

Ettore:

First try to use the camera in manual and the strobe in manual. Set up the camera for 1/125 second and f:11. Then set up the strobe to full power manual. See what you get. If it is still too dark let us know. What i think is happening is that the strobe is firing on the pre-flash not on the main flash and so the picture is not being exposed properly. In other words, TTL is NOT working well. Try all manual and let us know.

Bill

Hi guys, sorry for replying. Unfortunately I had a little personal trouble and I couldn't connect for a certain time. In my next dive (my holidays are over), I hope still in Sept, I will try your very interesting suggestions and I let you know about the results. Thanks again. Ettore

dont forget you can practice on land, before your dive.

if you're shooting Manual with TTL, as Lee outlined, then using your normal flash (580exII) will give similar results as the DS125.

I always shoot Manual with TTL flash, unless the ambient light is enough for me to shoot in Av with enough shutter speed for the subject (and i want a balanced shot).

I also program the Custom modes so i can quickly switch between flash and no flash.

Manual with flash (lower iso)

Av with no flash (higher iso)

Av with flash (medium iso)

I find TTL works great. So i suggest practicing on land and understand the above relationships before diving.