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TTL, a-TTl, e-TTl, e-TTL II

flash strobe canon

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#1 Ram


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Posted 06 July 2014 - 02:12 PM

I have been reading about the flash systems and I am a bit confused. May be somebody can clarify it for me.

The strobes in the market, for example Ikelites, say that they are TTL compatible, yet there are TTL, a-TTL, e-TTL, and e-TTL II systems. So, does it mean that these TTL strobes only work with the original TTL system ( designed for film cameras),or they also include the newer e-TTL and e-TTL II? In other words, by saying they are TTL compatible they are generalizing to include the newer systems?



#2 Tom_Kline


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Posted 06 July 2014 - 03:27 PM

TTL without any extra letters refers to the Nikon/Nikonos film type TTL as you surmised - light was measured bouncing off of the film during the exposure and the flash quenched accordingly. The newer systems are mutually incompatible. Most use pre-flashes to determine the flash exposure prior to taking the picture. You need a separate adapter, if one is available, for each type.

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Thomas C. Kline, Jr., Ph. D.
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Housed digital cameras: Canon EOS-1Ds MkII, EOS-1Ds MkIII, and EOS-1D_X; and Nikon D1X, D2X, and D2H. Lens focal lengths ranging from 8 to 180mm for UW use. Seacam housings and remote control gear. Seacam 150D and 250D, Sea&Sea YS250, and Inon Z220 strobes.



#3 Ram


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Posted 07 July 2014 - 07:46 PM

You are right Tom_Kline, but I also got a mail from Ikelite saying that their "TTL" does work with e-TTL II, with Canons and Nikons and keep the  protocols simply “TTL” for ease in explanation. 


#4 bvanant


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Posted 08 July 2014 - 07:56 AM

There is a lot of confusion about the whole TTL universe. As far as I understand it (about 2 cm worth) eTTL is Canon's proprietary TTL system that lets Canon cameras talk to Canon strobes. iTTL is Nikon's version of the same. If you are shooting a Canon camera and using a housed Canon strobe then eTTL works fine (if you have the right electrical connections). Same for Nikon.  Neither Canon nor Nikon have published their TTL protocols (they want you to buy their stuff) but several folk have figured out how to emulate Canon and Nikon TTL protocols. If you use electrical sync then there are converters (Weikamp, S&S, Ike) that plug into your cable/hot shoe) and allow you to get TTL functionality from strobes that can speak that version of TTL. If you are using optically fired strobes then you need to emulate TTL (sTTL) for example. This typically works by sending a pre flash from the strobe to the subject then calculating the correct exposure then exposing the scene with the correct strobe duration. 

Hope this helps


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