How exactly does TTL w/ external slave strobe work?

[Matt S.]

I posted this question in my camera maker's sub-forum but perhaps it should have gone here, in the general lighting area. I'd be most appreciative if anyone well versed in TTL lighting could give my question a look.

http://www.scubaboard.com/forums/se...be-used-external-strobe-ttl-calculations.html

Bottom line: Can I keep the fiberoptic cable in place but block the internal strobe, or will that mess up the external strobe's TTL magic? The internal strobe causes lots of backscatter in my 10 ft vis home waters.

 

[slowhands]

When using TTL flash, the camera exposure sensor reads all the light reflected back from the scene, whether from ambient light, internal flash or external flash. It turns off the flash when it determines a proper exposure has been made. You can and should block your internal flash to prevent backscatter - it will work fine.

 

[Nemrod]

Your S&S DX camera is a "P&S" camera and does not support actual TTL. The YS strobe has a built in control system (similar to the Inon S/D/Z strobes sTTL feature) that is designed to boot strap the camera strobe, in other words, to mimic it. The camera does not know or care where the strobe source light is coming from, internal or external, as long as it gets enough for the exposure to be happy.

As has been stated, in the other forums where you asked this question, you need to fully block the internal camera strobe, assuming there is an optical cable link so that the YS strobe can sync and boot strap the internal strobe.

The internal camera strobe should be set on Auto (vs any Manual selection) and Forced for the simulated TTL to function. The exact selection of settings depends upon the camera menu functions available and your selection of Program vs Shutter/Aperture Priority etc. I do not believe the DX camera allows simulated TTL in Manual Exposure mode. In Manual exposure mode on your DX you will operate the YS strobe in Manual as well. Some Inon strobes offer a third operating mode, External Auto, where a built in exposure system in the strobe is provided allowing automatic strobe exposure while the camera is in Manual exposure mode, YS strobe I do not think have this feature unless I am mistaken, for what it is worth.

N

 

[Matt S.]

Thanks for the replies. I got out the duct tape and confirmed that TTL or (faux-TTL as it may be) still works. Interestingly, it seems to work when the camera is set on manual too--exposures came out fine, strobe power varied depending on what I shot at, and the strobe's green "I just used TTL" light came on after firing.

I wish the manufacturer would cover this stuff better, or at all, in the material that comes with the camera. The DX-2G comes with a great manual, but I have a feeling it is mostly Ricoh's work. The YS-01 manual has a little bit of setup info, but omits a lot of important information. There is a S&S "setup sheet" PDF too, but it's also pretty useless.

So thanks again to you and the others who have taken the time to answer my questions, even when I get impatient and post to 2 forums in the same night.

 

[Nemrod]

So thanks again to you and the others who have taken the time to answer my questions, even when I get impatient and post to 2 forums in the same night.

Yeah, this stuff is complicated and somewhat confusing

I don't see how the TTL could work in camera Manual mode unless the Ricoh has auto strobe in manual, which would be unusual for this type of camera, but, who knows If so that is a great feature.

Good luck, post your results.

N

 

[cardog]

Your S&S DX camera is a "P&S" camera and does not support actual TTL. The YS strobe has a built in control system (similar to the Inon S/D/Z strobes sTTL feature) that is designed to boot strap the camera strobe, in other words, to mimic it. The camera does not know or care where the strobe source light is coming from, internal or external, as long as it gets enough for the exposure to be happy.

As has been stated, in the other forums where you asked this question, you need to fully block the internal camera strobe, assuming there is an optical cable link so that the YS strobe can sync and boot strap the internal strobe.

The internal camera strobe should be set on Auto (vs any Manual selection) and Forced for the simulated TTL to function. The exact selection of settings depends upon the camera menu functions available and your selection of Program vs Shutter/Aperture Priority etc. I do not believe the DX camera allows simulated TTL in Manual Exposure mode. In Manual exposure mode on your DX you will operate the YS strobe in Manual as well. Some Inon strobes offer a third operating mode, External Auto, where a built in exposure system in the strobe is provided allowing automatic strobe exposure while the camera is in Manual exposure mode, YS strobe I do not think have this feature unless I am mistaken, for what it is worth.

N

I have my DX2G internal flash set at manual (1/8 power) and I shoot with two YS01 strobes set in TTL and the camera in full manual. Usually f8 1/500 shutter speed.
Works just fine........

 

[Matt S.]

Ron, in that scenario how do you adjust overall exposure compensation?

I set the camera on force-flash but don't choose a manual power level. Then I can use the flash EV comp for overall exposure fine tuning.

Some have said that the dial on the YS-01 will do exposure comp when in TTL mode but in my above-water tests I have not been able to get that dial to do anything.

 

[cardog]

The only thing that I've been adjusting is the strobe power. When in TTL you can adjust the power down only.
I set the internal flash at 1/8 to save battery time.