HELP (URGENT): TTL settings (Camera + DS160's)

I'm hoping someone can help with a really obvious question...

Right before I I left for this trip to Indonesia I asked Ryan at Reef Photo to modify one of the bulkheads on my Aquatica housing (D200) to work w/the Ike TTL converter and 2 DS160's.

I set it up this morning and everything (during testing) is really (really) overexposed. I'll admit I'm pretty jet-lagged right now and I haven't shot TTL w/a DSLR before, so I likely have something set up wrong.

Can someone pls help w/the camera settings?

Should I be shooting P, A, or S? I know I have to dial in the EV (potentially), but it's not close right now...

The converter is set on TTL, and the strobes are firing... so I'm guessing it's the camera setting.

Quick answer would be much appreciated - I'm set up using manual right now (so not losing any dives) but would like to try the TTL over the next couple of days.

Thanks,

- Matt

I don't have any experience with the Aquatica housing, but I always shoot M underwater. That way I have full control over the aperture and the shutter speed. I would think you'd never want to use P. A or S may be of value if you want expose for ambient light which sort of defeats the purpose of using strobes.

As I said, I always use M. If I want to include background lit by ambient light I adjust the shutter speed as required. I adjust the aperture for the desired depth of field.

If you are getting overexposed shots, check at what aperture the camera is choosing. Perhaps it is opening up too much and the strobes don't shut off quick enough. Also what EV are you dialing in?

If you set the camera to M does it override the TTL? I'm shooting manual now, but I'd like to try out the TTL set up I just had added to my housing...

Sorry for simple Q's - I realized I haven't shot TTL since film days...

Thanks,

- Matt

I don't have any experience with the Aquatica housing, but I always shoot M underwater. That way I have full control over the aperture and the shutter speed. I would think you'd never want to use P. A or S may be of value if you want expose for ambient light which sort of defeats the purpose of using strobes.

 

As I said, I always use M. If I want to include background lit by ambient light I adjust the shutter speed as required. I adjust the aperture for the desired depth of field.

 

If you are getting overexposed shots, check at what aperture the camera is choosing. Perhaps it is opening up too much and the strobes don't shut off quick enough. Also what EV are you dialing in?

If you set the camera to M does it override the TTL? I'm shooting manual now, but I'd like to try out the TTL set up I just had added to my housing...

 

Sorry for simple Q's - I realized I haven't shot TTL since film days...

 

Thanks,

 

- Matt

No. Set the camera to manual exposure. In a room away from strong sunlight, set aperture to f/16 and shutter speed to 1/125. Take a shot at something close where the entire shot is lit by strobes. Check exposure (histogram). Change aperture to f/11. Test fire. Check exposure (histogram). If TTL is working properly, the second shot should be exposed like the first shot. Tweak your aperture some more and see if you get good results.

Everything could be overexposed because your exposures settings, possibly.

If you set the camera to M does it override the TTL? I'm shooting manual now, but I'd like to try out the TTL set up I just had added to my housing...

TTL for flash is completely separate from the exposure settings for ambient light. TTL Flash will work in all settings, including manual.

The TTL logic works with the flash and effectively turns it off when "enough" light has reached the sensor. I say effectively, because with digital it works different from film. With film, there was a sensor reading off the film itself and that actually turned the flash off after there had been enough light. That doesn't work with digital so instead a few very short pre-flashes are used to determine the length of time the main flash needs to be on for.

Just set the camera to manual. Set the shutter speed and f/stop you want. As long as the flash to subject distance - f/stop combination is within the range of the guide number of the flash, you should get a correctly exposed image. i.e. the distance times the denominator of the f/stop should be less than the guide number. The DS160 has a guide number of 24 in metres for an ISO of 100 above water. That would be 12 for ISO 200. So, if the subject is a metre away, your f/stop should be f/11 or less at ISO 200.

If you set the camera to M does it override the TTL? I'm shooting manual now, but I'd like to try out the TTL set up I just had added to my housing...

 

Sorry for simple Q's - I realized I haven't shot TTL since film days...

 

Thanks,

 

- Matt

Yes, do go with the "M" setting. You will have more flexability with you shutter speed. Check your camera settings to ensure that you don't have some funky setting. Do a simple TTL test sans film of course. Get more sleep.

Bob

from Ike site:

"Can I verify that my strobe TTL is working?

The camera must be loaded with film, or a strip of film placed over the pressure plate. Set the camera at its widest aperture (like f/2.8) and trip the shutter while the camera and strobe are aimed at a very close subject. The strobe should produce only a small blip of light. Repeat this with the lens covered and the strobe should produce a full power flash.

TTL failure is frequently caused by low batteries in the camera. This is true for both SLR and Nikonos cameras. Low batteries can even cause the shutter to lock in some SLR cameras. Batteries are one of the first things to check if a problem occurs. "

Ikelite Strobe heads need to be on TTL, too, as you are controlling TTL flash from your camera flash +/- even in "M" mode.

Switch to A mode and try. Nikon dSLR cameras can "float" the Shutter speed from something like 1/60 - 1/250 or whatever your max synch speed is for flash and not overexpose your background in this mode.

Good luck,

dhaas