TTL accuracy mainly depends on TTL Converter and right cable. I know a lot of people who shoot now with modern TTL converters and fiber optic or electric cables, getting 95% successful shots. Of course automatics simplifies the work of underwater photographer.
But if you use a camera built-in flash for optical TTL synchronization, in some cases it works good enough, but in many cases it gives very different results for TTL, because of technical reasons. Better use TTL-converter.
You can use TTL with Ikelite strobes on other housings too, because many TTL-Converters officially support Ikelite strobes. Such TTL circuits are available for Nauticam, Sea&Sea, Aquatica, Seacam, Subal, Sealux, Hugyfot, Isotta, and some other housings.
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