Strobe problem/question

[joby]

Hi,

wondering if all of you U/W photo experts can help me out. We're going to use the camera/strobe on a January 5 cruise.

We're divers. I am NO photo pro. We just like to take some pictures of fish swimming away, turtles-- heads only, nothing but blue water, etc. --the usual unskilled photos that photo dummies take

We have a used Sealife U/W flash that we use with our Canon Powershot S1 IS which has a housing. Many times while underwater, the strobe does not go off (making the pictures blah gray/blue).

When we try the strobe on dry land, it goes off just fine. We even treid it on the camera in a black bathroom and it took a fine picture of the bathtub and towels We took it to the pool last night for the SCUBA class to try it in the pool--worked fine.

Why does it not go off MOST of the time underwater regardless of the depth while we are diving?

 

[f3nikon]

One of the problems maybe that the camera's flash is not reaching the strobe to fire it. In the bathroom or the pool the flash has the walls or mirror or towels or other objects to reflect or bounce the light back to the strobe.

When shooting in open water the light just keeps going unless it hits an object close enough to reflect the light back to the strobe. Another reason to shoot close, like one foot or less.

Test this by shooting on land at the open sky and see if it still fires.

Or sink some money on an optical sync cord.

 

[gert7to3]

Which SeaLife strobe are you using? Does it have a fiber optic cable and are you using it? What are the exposure modes you have your camera set to?

If you are not using the fiber optic cable, stuff in the water may be attenuating the camera flash pulse. This interferes with the strobe's slave trigger. The juxtaposition of the strobe to the camera may also thwart the trigger pulse. Finally, if you are using an automatic exposure mode, then your camera may not even trigger the flash due to high ambient light levels in the water.

 

[joby]

I'll answer the best I can--remember I'm a photo dummy

The strobe is a SeaLife SL 960 (it also says component SL96001). It has no fiber optic cable. The strobe screws onto the bottom of the camera housing.

The camera is usually set at "auto".

The flash goes off in the house unattached to the camera housing, in the house attached to the camera housing, attached to the camera housing at the pool, in a blackened bathroom, and sometimes (not ususally) at depth underwater. So the strobe seems to work everywhere except when we need it to underwater

Does that help answer your questions?

 

[scubaho]

You might need to deflect the internal flash upward so the strobe sensor sees the flash. I would not have the camera in "A" mode. Pick shutter priority and set to 1/60 or 1/90 sec.
You can use duck tape on the front of the housing to deflect the light.

 

[gert7to3]

Go to the "Tips and Techniques" thread in this forum and read the first two posts by Gilligan and Alcina.

Here's a review of your camera which may be clearer and easier to understand than your regular manual: Digital Cameras - Canon PowerShot S1 IS Digital Camera Review, Information, Specifications

What sort of settings do you have available for your strobe?

The general way U/W photography works is to use manual mode for your camera.

1) Set the ISO low, usually around 100.

2) It's probably best to use a macro setting for your camera.

3) Set the Aperture small ƒ5.6-ƒ8.

4) Take some pictures, without flash, at depth. Adjust your shutter speed to obtain the most pleasing background color and saturation. Faster shutter speeds will make the background darker, because you are under exposing the scene. You should get flash synch with shutter speeds as high as 125 or so.

5) Use your flash adjustments to illuminate your subject.

Work out some sort of masking reflector as mentioned by scubaho. The technique here is to get light striking your strobe's slave trigger port while masking the camera's internal strobe from the water column between your lens and subject.