Help!! Strobe for only auto focus camera!!

Some mounth ago someone writed:

"if a digicam uses a pre flash to measure exposure then how does this work if you have the built in flash covered by an slave/optical/etc sensor to prevent backscatter when using a strobe? In other words, you can get the strobe to fire using some sort of slave but if you cover the built in flash then the function of the preflash is negated."

Now I have the same question because I want to buy a strobe for my canon s400. I think I'll get Epoque es-150.

Can anyone help me?

Carlo

There are a lot of tips and tricks here. You can cover the camera's internal flash with a piece of developed film. It will block the light, but not the IR that will trigger your strobe.

You will need a flash that is compatible with your Canon's preflash system. The S400 is a great camera topsides, but its lack of manual controls will make it very hard to get good photos underwater.

HTH

James

Thank you!!

I know my camera's limit!!

I'd like to know if I put a piece of developed film in front of the diffuser can the pre-flash leak the film? and overall, can the CCD determinate the optimal aperture and exposure timing?

When operating in slave mode, think of the builtin flash as a timing device for the strobe: builtin flash on -> strobe on, builtin flash off -> strobe off. Twice for each shot for preflash TTL. The preflash that's required to measure exposure comes from the strobe.

The exposed film trick cuts out the visible part of the light from the builtin flash. The infered will get through and trigger the strobe.

For TTL to work, the strobe has to be fast enough to follow the flash, and also has to be designed to turn on AND off with the flash. Some will only follow the flash on.

Thank you Herbko!

Excellent observation!

Do you know which strobe can turn on AND off with built in flash?

I'd be interessed to get one of this: Epoque ES 150 DS, YSD25auto or YS90auto ( but this is the last choise, too expensive!)

Carlo

I use a S40 and a S50 in a WP-DC 300 Housing.

I Use the Exposed Slide Technique.

As Far as I know you can't use ttl with the Epoque and the Sea & Sea. You have to shot manualy. The Internal Flash only triggers the Slave.

The only way known to me is the Ikelite TTL-Sensor used with a DS50 or a DS125 (which I use).

Ike doesn't recommend it though for small cameras like the S-Series and the Ixuses, but i get pretty nice results with it.

But I also tend to shoot manualy more often, so when I would decide again, I would use the Manual Sensor.

Simon