pentaxuser
Member
It doesn't actually tell you anything.
It simply permits the TTL flash metering system to work the same way as it would with film.
And that metering system, and the feedback systems built into, are what tell you things - primarily about whether the flash(es) employed have sufficient power to be able to illuminate the subject sufficiently.
Essentially, it allows the TTL flash metering system to give you a go/no go result, without having to waste any film.
Thanks Matt I was simply ignorant of what information was fed back to the user
pentaxuser




And it was mostly MF. i-TTL worked pretty well when you needed it for dynamic situations though (most of the issues we had was with compatibility).