D300 built-in flash, Part 1: Blinding speed

Started Dec 25, 2008 | Discussions thread
atigun Contributing Member • Posts: 730
Very nice - here are some older strobes

Hi Marianne,
Very nice and educating tests. Thanks for the efforts!

Below is a test I performed > 10 years ago in the area of TTL (not iTTL) quenching of strobes. I was interested in how SB-24 would work with a bigger underwater strobe, the Ikelite SS200. The light sensor is a TLS252/TI light to voltage converter that I obtained from Scandinavian electronic supplier ELFA. The dotted lines are 1/2 to 1/8 power curves. The test revealed that this is somewhat problematic due to the slow light output curve of the bigger circular flash tube of the SS200. I is also evident that SB-24's half output quenching time is about 1.5 ms (1500 us) which is about 2x that of the D300 on-board flash:

If both of these strobes are shut off at the same time by TTL quenching, the relative light output between the two strobes will be quite variable, and the SS200 will never reach full light output unless the SB-24 is non-quenched.

I assume the CLS system circumvents this problem by each strobe "knowing" what it's quenching time should be at different light output so that the camera only needs to inform the strobe about the desired relative light output?


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Atigun valley, a place north in Alaska

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