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Does anybody make a properly working TTL trigger for Canon?


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#1 saudio

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Posted 06 March 2018 - 07:43 PM

I shoot a Canon 7DII and Nauticam.  I'd really like to have a TTL trigger that solves the problem of using the onboard strobe as a trigger because of the awful recharge delay after a few frames with the onboard strobe.

 

I purchased the UW Techincs model and used it for a week, and discovered that after the first shot you have to wait 2-3 seconds before the next shot or you get a greatly diminished strobe output (dark, useless image).  To me that is no better, in the long run, than the delay with the onboard strobe.  I sent it back and the shop checked with the manufacturer (I had hoped I received a defective unit) that this is a normal condition for this device.  

 

The Turtle version doesn't seem to have the Canon problem solved either.  

 

Does anybody make one that works properly?  

 

thanks

 

Mike



#2 Pavel Kolpakov

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Posted 07 March 2018 - 02:35 AM

Hello Mike,

 

Z240 recharges 1-2 seconds after energy-intensive Canon double flash, but not TTL-Converter. Double flash includes Pre-flash + main flash, with very short interval between them. Such double flash discharged Z240 capacitor significantly. Z240 requires recharge before next TTL shot for getting required lighting accuracy.

Bigger size strobes (for example DS-161 or YS-250) don't have such effect, because of large capacity of main capacitor and a bit different control logic. Using those strobes, it is available to get enough quantity of shots in fast series at the same TTL configuration. 

So, the effect refers to underwater strobe specific.

 

By the way, Nikon TTL doesn't have such significant effect with Z240, because of shorter Pre-flash than Canon in underwater systems. 

Canon TTL camera needs to receive back significant energy Pre-flash for accurate and stable exposure rating, it becomes more important underwater than on land, because of absorption of pre-flash by water. Canon camera TTL measuring system is less sensitive and stable than Nikon, unfortunately. That is why the large energy Pre-flash for underwater usage was a forced decision for TTL-Converter for Canon. Using that solution, UW Technics has reached high TTL accuracy and stability underwater for Canon cameras.

 

Of course, you can try Canon TTL circuit from any other manufacturer. Maybe, it will have a shorter Canon Pre-flash, which would be better for fast serial shooting with Z240. But you have to compare the TTL accuracy and stability in this case. Don't forget that flash exposure accuracy is the main task for TTL.

 

If you interested in continuous (serial) shooting, look to User's Manual of your board, - for getting stable flash exposure at fast continuos shooting with underwater strobes, it is recommended to switch system to "Manual" mode (by camera menu, or by strobe switch). This case you exclude Pre-flashes, make underwater strobe recharging faster. Using Manual mode and small strobe intensities, you can get a lot of shots in fast series.


Edited by Pavel Kolpakov, 07 March 2018 - 05:06 AM.


#3 saudio

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Posted 07 March 2018 - 07:31 AM

Hi Pavel, thanks for the reply.  Are you with UW Technics?  Everything you said is correct and I understand.  However, if you use the onboard strobe in TTL mode, you can shoot continuously until the recharge time of the camera strobe starts to lag.  So it is clearly possible for the Z240's to be able to shoot continuously in TTL, but it seems the Technics product had not been able to replicate the Canon TTL exactly.  

 

Some photographers may find the lag time between shots to be acceptable, but for me, having to count in my head between frames to be sure I get a properly exposed shot is not something I can live with.  And I counted at least 2 full seconds lag with the UW Technics board.  

 

It seems to work well other than the lag, so if you have strobes that are compatible it would be very useful.  But I'm still looking for something that works properly with my 240s (now 330s).  

 

I would suggest to UW Technics that they mention in their user manual this issue with lower powered strobes.  I spent an awful lot of time on my trip trying to figure out why it was not working properly.  



#4 buddy

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Posted 07 March 2018 - 10:05 AM

there are 2 dedicated new modules from Subal for Canons, but honestly i don't know whether they are any better since I am a Nikon shooter...

check it out here:

http://www.subal.com...lectronics.aspx


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#5 saudio

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Posted 07 March 2018 - 11:08 AM

there are 2 dedicated new modules from Subal for Canons, but honestly i don't know whether they are any better since I am a Nikon shooter...

check it out here:

http://www.subal.com...lectronics.aspx

Thank you Buddy!  I immediately called my dealer to ask whether these could be adapted to my Nauticam housing, turns out these are the same UW Technics circuitry just fitted to Subal.  But I do appreciate the idea just the same.  



#6 Pavel Kolpakov

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Posted 07 March 2018 - 11:44 AM

Mike, i understand that you want to get normal TTL exposure at fast serial shooting camera mode ("Continuos shooting mode"), maybe 3fps - 7fps or faster. You don't like 1-2 seconds waiting for Z240 recharging for getting accurate TTL.  i can understand it.

Did you try such fast serial shooting mode with Z240 TTL in the past?  Because, using Z240 strobe in TTL mode, Independently of anything, every next shot in fast series has significantly less lighting than previous shot, - Z240 does not have enough time for recharging and it causes different pre-flash (and different main flash) at every next shot. The idea of TTL metering does not work normally for serial shooting with small uw strobes.

People usually shoot in "single shot" camera mode with Z240 TTL to get accurate TTL exposure. This is independently of camera brand and TTL-Converter brand.

 

But Ok, you can find any TTL-converter which has very short pre-flash (for Nikon, Canon, or other), and get 2-3 shots per second using Z240 this way in series, but pay attention that you cannot get normal TTL exposure in series (there will be very different flash exposure for all 3 shots).


Edited by Pavel Kolpakov, 07 March 2018 - 12:57 PM.


#7 saudio

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Posted 07 March 2018 - 12:50 PM

Mike, i understand that you want to get normal TTL exposure at fast serial shooting camera mode ("Continuos shooting mode"), maybe 3fps - 7fps or faster. You don't like 1-2 seconds interval for Z240 recharging for accurate TTL.  i can understand it.

Did you try such fast serial shooting mode with Z240 TTL in the past?  Because, using Z240 strobe in TTL mode, Independently of anything, every next shot in fast series has significantly less lighting than previous shot, - Z240 does not have enough time for recharging and it causes different pre-flash (and different main flash) at every next shot. The idea of TTL metering does not work normally for serial shooting with small uw strobes.

People usually shoot in "single shot" camera mode with Z240 TTL to get accurate TTL exposure. This is independently of camera brand and TTL-Converter brand.

 

But Ok, you can find any TTL-converter which has very short pre-flash (Nikon, or other), and get 2-3 shots by Z240 this way in series, but it will not be normal TTL exposure (very different flash exposure for all 3 shots).

Hi Pavel.  After I returned home from my trip with the UW Technics TTL board, I did a comparison bench test, using both the Technics board and the onboard strobe taking rapid secession shots.  I did not get the same results you describe above, the three shots I took with the onboard flash TTL all seemed to be exposed exactly the same.  I made a video of this test to send to my dealer to help explain the trouble I was having.  I can post the vids here if you like.  



#8 Pavel Kolpakov

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Posted 07 March 2018 - 01:02 PM

.... I did a comparison bench test, using both the Technics board and the onboard strobe taking rapid secession shots.  I did not get the same results you describe above, the three shots I took with the onboard flash TTL all seemed to be exposed exactly the same. ...

Do you mean pop-up flash on camera body? On air?  There is a difference with underwater usage. On air the short enough pre-flash on Canon TTL system works normally. But water absorption required from developer better to encrease pre-flash to get stable results for Canon TTL metering system, - it plays the main role. 

 

Of course, not all manufacturers pay such attention on TTL accuracy underwater for Canon, and you can find any Canon TTL circuit on the market which has short pre-flash, and hope you can use it for serial shooting with Z240 (3 shots per second), although TTL exposure will be different at each next shot in series. 


Edited by Pavel Kolpakov, 07 March 2018 - 10:08 PM.