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Another TTL-Manual question

Sea and Sea Canon 5D Mark IV TTL optical converter YS-D2

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#1 stilly

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Posted 21 December 2018 - 07:29 AM

I have a Canon 5D Mark IV with a Sea and Sea MDX 5D housing, Sea and Sea TTL optic converter & 2 YS-D2 strobes. 

I've been having intermittent problems with exposures in TTL mode for all ranges-macro as well as wide angle. I have all the modes set correctly Blue, blue, blue, but sometimes the left strobe not synching fully or at least exposures are under, or sometimes it looks like they didn't fire at all.... Through process of elimination, I've replaced the converter, swapped cables, even replaced the strobe. If I switch to manual Green, green, green, everything looks much better exposure wise and consistency. I don't mind this but I'm surprised that the TTL isn't working better. I don't think it would be my camera, but anyone with similar gear that could give insight would be greatly appreciated.



#2 ChrisRoss

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Posted 21 December 2018 - 10:33 PM

TTL is notoriously finicky underwater particularly for wide angle and a lot of whether it is successful or not has to do with what the camera tells the flash to do.  There's a whole pile of technical details to get the TTL converter to mimic the onboard flash or in your case interpret the signals coming from the camera to send to the flash.  But if the camera can't work out that the water is not the subject, it just won't work, so this could be a problem in either macro (thinking black BG subjects smallish in the frame) or wide angle shots.  That is why manual flash is so popular for UW photography and it's generally not as hard as it seems to get right and requires a good estimate of distance to subject to set you flash power.  If you pick an aperture to stay at it helps a lot.  Assume you have the settings for which flash you are using right on the converter itself.

 

Having said that if one strobe seems to work OK and the other does not that would indicate it's not getting the proper triggering signals from the the TTL converter.  As i understand it the S&S TTL converter connects  via fibre optic cables.  So I would check that the LEDs on the TTL converter are aligned with the windows and also check your optic cables.  If you swap the LH one to the RH and the fault moves that's your problem.  Physically swap the cables and also just swap ports on the camera to test out if it's the cable or something at the TTL converter/window end.  S&S strobes don't have a super sensitive trigger so need the best quality cables, I believe the new S&S cables are one option that works.



#3 stilly

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Posted 22 December 2018 - 04:47 AM

Thanks for your input Chris,

I've done the cable swapping & strobe swapping and even tried a new TTL converter.

Still getting weird and inconsistent results. This all started after my last dive trip where I had TTL issues. Now I'm trouble shooting above water and wondering if some issues would be different if I was testing underwater. Light is light but currently, I'm thinking manual may just be a better way to go for me.



#4 Roger-Botting

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Posted 30 December 2018 - 01:10 PM

A dumb mistake I made a few dives back. I accidentally, during a dive, set the camera to auto bracket. Yes, normal, one stop under, one stop over exposure.

But seeing your last post, if you are sure that you have made sure everything is set properly, borrow someone else's identical equipment and then test to see what is the problem peice.



#5 stilly

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Posted 31 December 2018 - 09:18 AM

A dumb mistake I made a few dives back. I accidentally, during a dive, set the camera to auto bracket. Yes, normal, one stop under, one stop over exposure.

But seeing your last post, if you are sure that you have made sure everything is set properly, borrow someone else's identical equipment and then test to see what is the problem peice.

After hearing quite a few people state that the TTL can be fooled so often, I've started experimenting with shooting full manual with my basic shooting distances known between super macro, macro and wide. I really only have to adjust one F stop between those different scenarios. Even if I didn't, I'd still be within the parameters of being able to fine tune exposures in RAW. Meanwhile, the light is so much more consistent & just overall much cleaner! I think I found my solution for my FF DSLR. Meanwhile my Sony RX100 VI works great in TTL.....Go figure!



#6 ChrisRoss

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Posted 31 December 2018 - 11:38 PM

TTL really depends on the camaera, once the technicalities of the slave electronics are sorted.  The camera is what interprets the pre flash and calculates the power of the main flash.



#7 stilly

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Posted 03 January 2019 - 09:28 AM

TTL really depends on the camaera, once the technicalities of the slave electronics are sorted.  The camera is what interprets the pre flash and calculates the power of the main flash.

Absolutely Chris! Since everything is firing I don't believe there's anything wrong with the strobes or TTL converter. I was just hoping that the camera would interpret the scenes more consistently.