Can someone explain TTL to me?

[Big Fic]

I understand "Through the lens" but with a digital camera and a strobe, how does it work?

Does the strobe connect to the camera via cable through the underwater housing?

Or are most digital cameras with strobes operated through slave mode?

Im looking at a Canon A85 or A95 with a Dc-30/DC-50 housing. How will a strobe be connected to the camera? Can it be connected via TTL or will it have to be a slave?

Im having a hard time understanding strobes and how they work with digital cameras :06:


Ive read that the Ikelite housing for the Oly 5050 has a sync cord that attaches directly to the camera. Is this rare for a digital camera?

Thanks for any help in understanding strobes

 

[jlyle]

TTL is available with some digital camera/housing/strobe combinations, but not all.

One problem with TTL and digital cameras is that the camera fires a pre-flash to meter the subject. Strobes that are going to work with TTL & digital cameras must be designed to work around the pre-flash.

Some camera/housing/strobe combinations, like the Ikelite housing for the c5050, allow for sync-connection to the camera and true TTL.

When using a housing like the PT-015 that doesn't have a through bulkhead connection, you can either use the Ikelite TTL controller or buy an interesting device from Germany that comes in two halves, one fits onto the hotshoe of the camera and the other is an external sensor.

Obviously, "slave" only fires the strobe and you control the output with the strobe.

When I first got my c5050, I started with a TTL controller and allowed the camera to do all the thinking for me. I've since taken the training wheels off and have gone to manual control and slaved strobes.

 

[ReyeR]

1. Hard-wired TTL: TTL flash or strobe photography at its simplest requires the camera to 'communicate' with the strobe using electrical signals. The camera tells the strobe to fire, the light bounces back from the subject and enters through the lens, sensors inside the camera monitor the amount of light and when the camera thinks the correct exposure has been attained it signals to the strobe to quench. For this to work the camera must be connected to the strobe (via the housing) using an electrical cable (sync cord). So the camera must have provision to connect an external flash (like a hot shoe), the housing must have a bulkhead (sync cord connector) and the strobe must have a sync cord connector as well. And the camera and strobe must 'understand' each other ie they must speak the same TTL language or protocol.

2. Slave TTL or 'Mimic' TTL (for lack of a better term): Here the 'slave' strobe will watch and copy another strobe ('master' strobe). This is done optically ie it'll have a sensor that is sensitive to sudden and bright changes of light. When the master strobe fires the slave fires, when the master quenches the slave will also quench. The 'master' can be an external strobe that is electronically controlled by the camera using a sync cord (as described above) or it can even be the camera's own built-in flash.

In your case (A84/A95 with a DC30/DC50), the camera doesn't have provision to connect an external flash and the housing doesn't have a bulkhead either. So, for TTL you will have to use method 2. A few examples are Sea and Sea YS90DX strobe with a Matthias Heinrichs Digital Adapter (http://www.muenster.de/~matthias/blitz/indexe.htm or http://www.camerasunderwater.co.uk/d_stills/flash/pages/mh_ttls.html). The Digital Adaptor has the the sensor that'll 'watch' your camera's built-in flash. It also contains the circuitary to control the strobe so it'll fire and quench in sync with the camera's built-in flash. Inon are also announced the D-2000 strobe which will (supposedly) work as a slave TTL strobe (D-2000 PDF: http://www.inon.co.jp/e_pdf/D2000_En.pdf and S-TTL explanation: http://www.inon.co.jp/e_pdf/STTL_En.pdf).

3. Manual Slave: If you are willing to forego TTL then you can also use many manual slave strobes with your setup. In this case the strobe will use the camera's built-in flash as a simple 'trigger'. It'll fire when the camera's flash fires but will not 'watch' and quench when the camera's flash quenches. You control the output of the strobe (and hence the strobe exposure) by manually dialing in an output setting. Strobes in this category will be the Ikelite DS-125 or DS-50 with the Manual EV controller, the Sea and Sea YS-90DX and the Inon Z220 amd D-180 (which is a semi-auto strobe).

I've read that the Ikelite housing for the Oly 5050 has a sync cord that attaches directly to the camera. Is this rare for a digital camera?

Usually only third-party housing manufacturers provide this. First the housing must have a bulkhead connector and second the strobe must understand the TTL protocol of the camera. Unfortunately the TTL 'language' spoken by different cameras are not the same so some sort of 'conversion' or 'translation' needs to be performed before they can 'understand' each other. With the Ikelite housing they provide a conversion circuitary the allows the Olympus camera to communicate in TTL with the Ikelite DS-50 and DS-125 strobes.

Olympus has also started including bulkheads in some of their housings e.g. PT-020 for the C5060. Using this bulkhead, individuals like Matthais Heinrichs now provide hard-wired (sync cord) TTL solutions with third party strobes (like the Sea and Sea YS90DX and the Inon Z220) by making their own conversion circuits.

Hope this helps and hasn't confused you even more.

 

[Big Fic]

Thanks for all the info


That helped me understand