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CL SF-40 and HSS ?


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2 hours ago, cirke said:

I have the very last Godox V1 on Sony A7R3 , TTL and  HSS are working fine  together but of course you can get a dark frame if you dont use -3/+3 compensation

How does it set the exposure/flash output level? Via a pre-flash? 

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Okay, that's a little different from the classic TTL flash metering originated by, I think, Olympus in the 1970s. With that system, the flash exposure was read off the film at X sync speed (1/60 or 1/125 sec), the flash quenched at the point of correct exposure, and the second curtain allowed to close. It had the advantage of only one flash burst, but obviously cannot work for HSS.

Pre-flash systems to evaluate exposure often have subtle side effects with some subjects: a good number of people will always have their eyes closed at the actual exposure time. On the other hand, such a system is compatible with HSS (although that need for exposure compensation doesn't really sound very good to me, perhaps I misunderstand). 

Fun stuff! 

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19 hours ago, cirke said:

I never use TTL with Godox , I use only M mode 

Hmm. TTL flash metering can be implemented in M, A, S or P camera modes. If you're using a flash mode with a pre-flash to evaluate exposure, it is most likely using TTL flash metering; there's no need for a pre-flash if the flash unit's sensor is reading the flash exposure, or if the flash is in manual exposure mode. 

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Okay, then I don't understand what you're reporting or how it works.

If the flash is in Manual exposure mode, why would the camera do a pre-flash, whether HSS or not? If HSS, the flash output for a given shutter time should be a known quantity to burn the tube long enough and the camera should just set it; if not HSS and up to the sync speed, it should just trigger the flash when the first curtain hits the correct open position, or just before the second curtain starts to close for trailing-curtain-sync, at whatever power output is set on the flash. 

There should be no pre-flash unless some kind of exposure evaluation is required, whether HSS or not, with that kind of system. 

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