Using Strobes on Shallow Dives

Hoping I can get some help here.  I'm in Aruba for the next few months, waiting out Covid 19.  I've been doing some shore dives here which tend to be very shallow (8-15 feet at some sights).  The problem is there is so much ambient light I'm not sure my strobes are working "as expected".  The colors seem very muted even though I appear to be close enough to my subject and the strobes are positioned correctly (from what I can see).  The photos look fine on the LCD, but when I get the photos in LR, they have a blue / green cast - not the bight colors that I am used to seeing.  At first I thought the problem was caused by my strobe batteries.  I've been using NiMH rechargeable batteries and I thought the batteries were no longer putting out the charge that they used to (they are a couple years old, but I only use them on dive trips). I bought brand new batteries, but I am still having the same output issues.  Next I started thinking the ambient light was so bright (combined with  poor camera settings) resulting in the low light from the strobe.  

I am shooting with a D850 with TTL converter and 2 Inon Z240 strobes.  I shoot in TTL because I'm a bit gun shy about going manual on the strobes.  I've read the Inon manual regarding the manual settings but not fully comprehended how to shoot in manual.

So my questions are:

1. Doe the bright ambient light make a difference regarding the strobe output?  If so, can you recommend some settings to use in TTL mode to boost the strobe power?  I typically use diffusers which I can remove in the future.

2. Would shooting the strobes in manual help to resolve the issues I'm having?  If so can anyone recommend a good tutorial  on how use the Inon strobes in manual mode.    

Any thoughts / recommendations are greatly appreciated.  Below are some of my typical photos on the shore dives.

You do not list your settings, that would help, but you probably need to increase you shutter speed to max sync speed and lower your ISO to minimum as a start.

I would say that there is almost no flash in those photos. It is hard to be sure without knowing the camera settings.

Shallow water makes no difference to strobe output! In bright conditions, the TTL circuit will reduce flash output, but you should still be able to see the flash's effects. 

Is the Pre Flash Cancellation circuit button on the strobes in the In or Out position? It should be Out. If it is In, the strobes will be ignoring the TTL output and firing on the preflash.

Manual is simple...Preflash cancellation button in the In position. Dial in Manual, control output with output dial...

I'm not sure how the TTL circuit in the housing needs to be set in order to be used manually though.

Assuming the pre-flash cancel button(magnet switch) is out as suggested by Adam, going to Manual is really the only way to get reliable flash exposures with wide angle- assuming you are close enough to your subject, preferably 1m (3ft) or less.  Some cameras are better with TTl than others, but generally TTL is only somewhat reliable with macro work.  In your case the camera decides there's enough light and doesn't need more flash exposure.    You need to have the RH dial at 12 o'clock - B position as your starting point

I assume you have looked through the manual for your TTL converter - you don't say which TTL converter you are using.  The Nauticam TTL converter for example has specific requirements for wire connected TTL for the Z-240.  It would help to have the full settings and equipment you are using.

To shoot manual with Z-240 strobes apart from switching to manual on the Z-240 you need to push in and lock the ACC button(magnet switch) on the strobe.  You are shooting with a D850 so presumably you are at f11-16 with a wide angle lens so you will want full power or close to it.  I would start with the RH output dial on 11 (green)which is half power.  Shutter speed at 1/250 and probably ISO at 400?  The camera/TTL board should go to manual flash output - you would need to review the manual for your board and the camera itself.   On settings the green numbers are f-stops for external auto mode - don't use that mode but they happen to sort of correspond with the flash output needed at that f-stop when you are somewhere around ISO400 and maybe 0.5m from the subject. 

Here is a guide for INON strobes in plainer English:  https://reefphoto.com/blogs/lighting/selecting-the-proper-settings-for-inon-strobes-1

Also note that the labels are colour coded.  S-TTL is yellow and the right hand dial has yellow labels corresponding to TTL mode.  This goes from 9 o'clock to 6 o'clock.  Outside of this region you are not in TTL any more.  Green is external auto - ignore this mode.  Manual is white and there is tiny wring on the RH dial in white stating at 9 o'clock it says "M -6" and next to the green 11 at about 8 o'clock it says "-0.5"  this is manual range from -6 stops from full power to -0.5 stops from full power which is half power.

Another thing to note is that on the Z-240 in the mode for pre-flash (magnet switch up)  the strobe still fires on both pre-flash and main flash - it doesn't actually ignore the pre-flash it just doesn't do anything about the preflash.  So ideally in manual you want to setup the camera/trigger combo to emit a single flash and have the magnet switch pushed/locked in.  This means you save battery power on the strobe.

If you have any difficulty with this info, get back to us with more details on the settings you use  and housing/trigger board type and we dig into it further.

BTW I tried out colour correcting your images and they came up reasonable, indicating there seems to some flash output happening.

Congratulations on getting your isolation in somewhere good for diving.

Being pedantic, the problem is not depth but ambient light. Too much ambient light means the strobes can't compete. Hence the need  to reduce ambient light as far as possible without reducing strobe effectiveness.

Affecting ambient light:

• aperture
• shutter speed
• iso
• depth
• clarity x depth
• latitude
• time of day

Affecting strobe light:

• aperture
• iso
• clarity
• distance from subject
• output power (and limited by TTL)

Aperture and iso are on both lists, so playing with aperture or iso are unlikely to make a difference. Shallow depth and clarity are the input conditions to your problem. 

Shutter speed and strobe settings are the adjustments already covered by previous posts. But you can only work those so far.

So think about time of day. Do your wide angle dives early and late in the day, when ambient light is reduced. During the midday hours, shoot macro, where small aperture and short distance from subject allows strobe power to easily dominate ambient light.

Round about 4-5pm the sun angle also gets low enough to create interesting dappled surface lighting and sunbeams to provide a really nice ambience to wide angle shots.

On 8/17/2020 at 1:17 AM, adamhanlon said:

I would say that there is almost no flash in those photos. It is hard to be sure without knowing the camera settings.

Shallow water makes no difference to strobe output! In bright conditions, the TTL circuit will reduce flash output, but you should still be able to see the flash's effects. 

Is the Pre Flash Cancellation circuit button on the strobes in the In or Out position? It should be Out. If it is In, the strobes will be ignoring the TTL output and firing on the preflash.

Manual is simple...Preflash cancellation button in the In position. Dial in Manual, control output with output dial...

I'm not sure how the TTL circuit in the housing needs to be set in order to be used manually though.

 

Adam,

Would not the flash output reduce to a very bare minimum and would hardly be discernible with TTL in the conditions described ? Or would the flash effect be visible to the naked eye as mentioned ?  This is quite interesting fo WA to understand. Though I have never used TTL BUT.......

Also a bit of work on LR and this image seems quite good. 

I think the rest has been explained in great detail by others out here.

Thanks,

Diggy

This is part of the problem with TTL, in that it is impossible to accurately diagnose the TTL circuit's "thought" process in exposing the way it did. In this case, neither the octopus nor the turtle has any obvious flash at all. Which suggests that either:

1. The flash did not fire or sync correctly with the camera.

2. The TTL's algorithm was "fooled" by the lack of contrast in the scene. 

I can see a possible case for (2) with the turtle image due to the white sand, although the turtle is some distance away from it, so I would expect that the TTL would attempt to expose correctly on it. However the octopus image shows no sign of flash at all, on any part of the image, including those close to the camera, leading me to suspect (1) is the problem

@diggy The color cast in the background created by white balancing the turtle in your edit above suggests to me that insufficient "white" (strobe) light arrived on it. This would suggest that the TTL circuit either didn't fire, or reduced power to such an extent that its effect is negligible. 

Thank you all for your help.  I did find that one of the Pre Flash Cancellation circuit buttons was in and the other was out on my strobes - so I'm sure that was not helping.  I checked the meta data in both photos and it did indicate the strobes fired.  Since I received such great information I decided to bite the bullet and try shooting the strobes in manual mode.  So again, thanks to all of you who provided such great tips about shooting in manual.

I have the Nauticam TTL convertor for the D850, so I had to move the "rotary switch" to "0" to specify manual mode.   I made sure both magnet circuit buttons were pushed in on the strobes, started using settings provided by Chris Ross and I am happy to say the color is back in my photos.  I had a few stinkers (a couple way too dark and one completely blown out) but overall I was pleased and surprised it wasn't as hard as I thought it would be.  It does require me to think a bit more when composing the shot, but this a good thing as I am not relying on TTL to compensate for poor camera settings (I didn't expect TTL to compensate - but very often it did and I got lazy).  

So thank you all again and Diggy - thank you taking the time to work your "LightRoom magic" on my turtle photo.  I was also able to restore some color, but I think you did a better job!!!  

Kind regards - 

Leslie

Glad to see it worked out.  If you keep constant distance from your subject then the flash exposure stays the same at any given ISO/aperture combination.  I found sticking to one aperture/ISO combination that works to balance with your shutter sync speed at least initially greatly simplifies shooting manual flash.   You might also like to try the controlled manual mode that is outlined in manual where you can change strobe exposure from the camera.

23 hours ago, adamhanlon said:

This is part of the problem with TTL, in that it is impossible to accurately diagnose the TTL circuit's "thought" process in exposing the way it did. In this case, neither the octopus nor the turtle has any obvious flash at all. Which suggests that either:

1. The flash did not fire or sync correctly with the camera.

2. The TTL's algorithm was "fooled" by the lack of contrast in the scene. 

I can see a possible case for (2) with the turtle image due to the white sand, although the turtle is some distance away from it, so I would expect that the TTL would attempt to expose correctly on it. However the octopus image shows no sign of flash at all, on any part of the image, including those close to the camera, leading me to suspect (1) is the problem

@diggy The color cast in the background created by white balancing the turtle in your edit above suggests to me that insufficient "white" (strobe) light arrived on it. This would suggest that the TTL circuit either didn't fire, or reduced power to such an extent that its effect is negligible. 

 

Thanks Adam,

Makes sense on all and especially the octopus bit...

Thanks

Diggy

I am so happy with the results using the strobes on manual.  It is getting easier with each dive.  Here are a few un-retouched photos (please disregard the composition on these - I just wanted to highlight the use of the strobes on manual).  I honestly never thought it would be so easy to get good shots.  I'm sure I can improve, but I figure these are a good starting point.  

I appreciate everyone who took the time to read my post and provided feedback.  

Kind regards - 

Leslie Howell

Well done Leslie!

You have it now.  That last shot is a keeper.

Now the fun begins.

Nicely done - no looking back now.

awesome :-) Yes I do agree the last shot is great.

Have fun  

Diggy