TTL systems in underwater photo

@Pavel Kolpakov I have just done some testing with the trigger. Just shooting in my house (dry), with no strobes hooked up, watching the trigger LEDs. I now suspect that my trigger is not defective, but rather that it has a bug (or more) in its implementation.

At first, it seemed the trigger was working perfectly.

Then I let my camera sit until it went into Power Save Sleep mode (or whatever it is called). Once it does that, THEN I am able to reproduce cases of the trigger sometimes not firing.

Related note: My camera is fairly new to me. It is set to the default of 1 minute before it goes into Power Save mode. It kept doing that to me repeatedly during my dives last week. I kept telling myself to figure out how to change that once I got out of the water - but I kept forgetting to look for the setting that controlled that, so it was like that all week (i.e. 1 minute until Power Save mode kicked in). Thus, it happened to me often.

One specific example that seems reliable to reproduce the problem behavior: Camera is in PS mode. Camera is set for Mid speed continuous drive. I press and hold the AF-On button and then pull the shutter release and hold it. The camera takes a second or two to wake up, but then it starts taking pictures (at several frames per second). The trigger LEDs never fire at all in that example.

I was also able to reproduce the problem another way, but it was not reliable to happen every time. Camera is in PS mode. Camera is set for Single Shot drive mode. I press AF-On and the shutter release, hold it briefly and then let go. Then start hitting the shutter release repeatedly. Sometimes the trigger LEDs would not fire.

It also SEEMED like it could be related to trying to shoot while the buffer was still clearing from the last string of photos taken.

Thoughts?

Friends asked to write some classic advantages of LED TTL-Converter vs small Xenon Flash (built-in flash, or  small optional) for synchronization with underwater strobes. They are as follows:

@Pavel Kolpakov aren't some of the issues reduced when using on-board flash in "Commander" mode, like on Nikon cameras?

10 minutes ago, Algwyn said:

@Pavel Kolpakov aren't some of the issues reduced when using on-board flash in "Commander" mode, like on Nikon cameras?

Yes, of course, it is possible to reduce some problems of xenon flash by applying various measures. And photographers usually do it. But in the post above i mean comparison in general. 

Thanks for this readout, Pavel. Fascinating stuff.

Some info and a question for @Pavel Kolpakov.

Pavel, the instructions for my trigger (for Sony a7rIV) strongly recommend to set the camera's Power Save timeout to 10 seconds. That means that after 10 seconds of inactivity on the camera, it goes to sleep. If something comes along that I want to shoot, it takes the camera around 2 seconds to wake up before I can start shooting.

That really does not work for me. When I am diving with and shooting sharks, it is not unusual to go 5 or 10 minutes (or more) waiting for the "right" composition to come together. I need to be ready during that whole time. When it happens, I will not often have 2 seconds of warning to get ready.

If I keep my camera "awake" during the (almost) entirety of each dive (whether that is by changing the Power Save timeout or by pressing the AF button or something else on the camera, to keep it awake continually), what is that really going to do to the trigger battery life? Is there some approach I can use to this that will give me reasonable assurance that I won't have my trigger batteries die during a dive day? Changing trigger batteries while out on a boat is not something I would even attempt.

On to the "information". I got my first UWT trigger back in Feb. It turned out to be defective. Bad firmware, from what Pavel posted. It seemed to work fine in living room testing. But, in a week in Utila I found that it would very often go out to lunch and refuse to fire. Reef Photo sent me a new trigger, but that had to wait to receive it from UWT, so it finally arrived yesterday.

I had done some extended living room testing with the old trigger and was able to reproduce the behavior of not always firing. Repeating that testing with the new trigger seems to indicate that the new trigger is "fixed".

But, I did find what I consider to be a bug in my Sony a7r IV's firmware. If the camera goes into Power Save mode (i.e. goes to sleep), I can press and hold the shutter release and the camera will take 1 - 2 seconds to wake up and then it will start capturing images. But, in that scenario, it will not fire the flash. It will only fire the flash if I hit the shutter release after the camera has awakened completely.

I tested this with the UWT trigger, in my housing (by just watching the trigger's LEDs). And I tested it with the camera out of the housing and my Godox V1 speedlight mounted in the camera's hot shoe. Same behavior with both items. Camera in M, with continuous drive. Camera goes to sleep. I press and hold the shutter release, or press and hold the BBAF, then also press and hold the shutter release. The camera wakes up and starts grabbing 10 fps, with no flash firing at all. If I just let go of the shutter release and hit it again immediately, it resumes grabbing images and the flash/trigger immediately starts flashing away.

I posted about this issue in an a7r group on FB and another member tested it on his a9 II and said it does not have this problem. His flash starts firing along with the shutter as soon as the camera wakes up.

I set my Godox on M and to its lowest power setting. It was kind of cool to see it flashing away at 10fps... Sometime, I'll have to test it to see what the max power level is where it can sustain flashing at 10 Hz.

43 minutes ago, stuartv said:

..... recommend to set the camera's Power Save timeout to 10 seconds. That means that after 10 seconds of inactivity on the camera, it goes to sleep. ....

Power saving time 10 sec is just a recommendation for maximum battery saving. Because TTL-Converter switches Off when camera goes to standby mode. As i know, many users set 1 minute, it is acceptable time for normal shooting. I agree, we have to write 1 minute in instruction.  If you need 2 min or 5 min active camera screen between two shots, no problem to set it.  Battery life will be some reduced, but not significantly for real dives. Sometimes you can keep your camera active the whole dive, if it is an important dive, no problem.

26 minutes ago, Pavel Kolpakov said:

Power saving time 10 sec is just a recommendation for maximum battery saving. Because TTL-Converter switches Off when camera goes to standby mode. As i know, many users set 1 minute, it is acceptable time for normal shooting. If you need more, no problem, set significantly more time. Battery life will be some reduced.

Thanks, Pavel. I will probably set it to 10 minutes, just to be safe.

Is there any way to tell when I need to replace the batteries, short of having them actually go dead?

1 hour ago, stuartv said:

Is there any way to tell when I need to replace the batteries, short of having them actually go dead?

Difficult to say for sure, because batteries on the market have different quality. Some of them keep high pulse power (for LEDs) good enough till the end of battery life, some batteries are rather bad in that. In common case, better change them significantly before they are go dead.

I have a few housings in my own usage. Mainly, i change batteries 1 time per year in them. But i shoot not very often. Anyway, if i go to an important dive trip, i change all batteries in my equipment before the trip, just for insurance. 

Some suggestions to "When to replace a Battery ?":

a) Start the dive trip with new or fully charged batteries, as Pavel suggests.  Use the best batteries available, they pay for themselves.

b) Use a digital voltmeter to measure the battery's voltage: If it is significantly below the battery's nominal voltage, replace the battery. One learns quite fast when to replace. Digital VOM's are quite small, light weight, inexpensive and readily available on eBay. Carry one on trips away from home, they can be given as a nice gift at the end of the trip.  

c) It is a good idea to carry spare batteries for the lamps, strobes, camera, vacuum leak detector... Don't forget the chargers. 

If you do not need them, a fellow diver will - great way to make new friends!

Given a typical NiMH discharge curve a digital VM is really not a good way to test AA batteries. Better to use a pulse load tester like the one from ZTS. With a voltmeter you might be at only 10% capacity and not know it.

My UT trigger uses CR2230 batteries, not AA/AAA. This is consistent with the moisture/vacuum alert system in the Nauticam housing. They are inexpensive enough to just replace if there is any doubt. 

On 5/13/2019 at 11:22 PM, davec13o2 said:

Hello Pavel,

Referring to the TTL converter for Sony a7Rii to be released, fitting it to a Meikon case, can you recommend a retrofit to the single hole in the top of the case for fiberoptic cables to two strobes? Or would the case have to be modified for two optical bulkheads? Below are diagrams of the Meikon case hole that fits their standard sync bulkhead.

Here are UWTechnics optional bulkheads specially developed for Seafrogs (Meikon) housings. These products (#91303-Optical, #91385-Nikonos, #91386-Ikelite style) have such a special rear part. So, uw strobes can be connected both optically and electrically to TTL system now.

@Pavel Kolpakov Do you know if the UW Technics TTL converter for Sony A6xxxx cameras in a Seafrogs housing supports the YS-110a strobes? I only see YS-D1 and above listed. 

3 hours ago, Lewis88 said:

@Pavel Kolpakov Do you know if the UW Technics TTL converter for Sony A6xxxx cameras in a Seafrogs housing supports the YS-110a strobes? I only see YS-D1 and above listed. 

Sorry, there is no YS-110a profile in that firmware. 

Firmware includes the following TTL-profiles:

Inon Z240,

Inon Z330,

Retra Pro,

Sea&Sea YS-D1,

Sea&Sea YS-D2 (China version),

Sea&Sea YS-250,

Ikelite DS-161, DS-160

Subtronic Pro-160

Subtronic Pro-270.

Thanks @Pavel Kolpakov 

I will have to go with the TRT electronics version it seems, even though I prefer the design and leak detector replacement setup of the UWT version.

Will any of the existing profiles, such as YS-D1, work for the 110a?

48 minutes ago, Lewis88 said:

Thanks @Pavel Kolpakov 

Will any of the existing profiles, such as YS-D1, work for the 110a?

YS-110a will work, but TTL curve is significantly different. As for me, the flash control will not be good enough. But that's up to you.

34 minutes ago, Pavel Kolpakov said:

YS-110a will work, but TTL curve is significantly different. As for me, the flash control will not be good enough. But that's up to you.

This is what I figured. I will go with the TRT electronics version.

11 hours ago, Lewis88 said:

......

Result will be the same with all manufacturers TTL boards, if YS-110a profile does not exist in firmware.

6 hours ago, Pavel Kolpakov said:

Result will be the same with all manufacturers TTL boards, if YS-110a profile does not exist in firmware.

TRT has the YS-110a as an available option in their firmware.