Which strobe for digital P&S has real TTL metering?

[DazedAndConfuzed]

Hi,

I noticed a few companies boast the term TTL for their digital P&S strobe. Are these real TTL (as in it will stop its light when the camera's imaging sensor has determined that it has received enough light) or just some term that they throw around for it having auto-exposure capability?

I always thought it shouldn't be that hard if the camera has TTL flash cability, just keep the strobe lit up as long as it is receiving light from the fiber optics cable.

I would have thought Inon S2000's S-TTL is another of one of those setup, except I don't see a light sensor on it, plus its specs said S-TTL feature is not available when camera's flash is set to slave mode. Its website talks about something about letting pre-flash through so the camera could do its metering based on it.

 

[Puffer Fish]

Welcome to the wonderful world for strobe control.

In concept, this is easy to do... in actual practice there are lots and lots of timing issues. Inon's sensor is at the back of the fiber optic cable, by the way.

You have the basic concept correct.. the camera sends out a preflash, which the strobe sees and sends out it's preflash, which the camera sees and thinks is it's own. When it gets enough light, it shuts off its preflash, and the strobe sees that and cuts off also, then they both fire, but the camera only sees the strobes light.

But for this to work, they have to both be timed the same... and they both have to use the same math to fire the main flash. Here are things that can go wrong:

1. The strobe fires at a fixed time after the preflash.. but the camera's timing is different.

2. The time delay is too long or too short for the strobe, so it has passed it's window to fire.

3. One assumes that the timing is one for one, but that is not always true...say the camera uses 1/4 the time for the preflash (1/4000 or a preflash = 1/1000 of a main flash, and the strobe usess one to one....

An example:

Oly has sea and sea make their small strobe...the UHL-1... this strobe will optical (there are lots of different names for this) TTL with either a panasonic or Oly camera....A sea and sea YS110 will also optically TTL with say a Panasonic LX-5, however, if you have a canon, the oly strobe will only work in slave mode, and yet the YS110 will work in TTL

So what is "slave".. it is just looking for a preflash (not timing) and then firing on the next light... manual strobe sync'ed to ignore the preflash.

But even this is not so easy. An LX-5, for example, when set to manual, will still us TTL for the strobe... but say a Canon S95, in manual will not.

I happen to love good optical TTL systems, so the trick is to get one that works and just go take lots of pictures.

 

[DazedAndConfuzed]

I guess for a strobe mfg to a product that will be compatible with all cameras out there, past, present and future, is always harder than it is. That's why the camera mfg usually makes the best strobe for their camera, but given UW is a afterthought, especially for P&S, which are basically when compared to other cameras in the topside world, are not much more than toy cameras. No camera mfg waste much time adding giant strobes for that catagory of camera.

I think I even read Inon has to take consideration the energy release vs/time as compared to onboard flashes. Lots of little factors to take into consideration.

 

[Puffer Fish]

The exception to this is Oly, which has two Underwater strobes made for their camera's...one of which is fairly powerful. The Inon issue is from putting a very strong strobe in a small sealled container, not the best for cooling.