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Extending arms or aim strobes outwards?

strobe arms technique angles

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#1 siltfilmer


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Posted 17 January 2019 - 03:06 PM

Reading through the forum I found two approach how to avoid backscatter in murky water for WA:

  1. extending arms to increase camera-strobe-distance
  2. using fairly short arms but pointing the strobes outwards to just feather the object with the edge of the light beam


I am still early in my underwater photography journey so I am interested in:

  • What is the preferred method?
  • Is there - besides the setup- any significant difference in the results?


I would assume that using long arms is most effective, but if there is no difference I would prefer the more compact setup :)

#2 ChrisRoss


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Posted 17 January 2019 - 05:27 PM

In general you extend the arms as your subject gets further from the camera, one rule of thumb I've seen is the strobe separation = subject to dome distance.  Pointing out can fine tune this.  There's lots of online tutorials on strobe positioning to look at.  I would say minimise backscatter rather than avoid, any particles right next to your subject will also be illuminated for example.  You also want to get the strobes back behind the dome particularly with a fisheye as the lens will be in focus on particles right next to the dome and the is a danger of producing flare.

#3 Fruitographer



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Posted 21 March 2019 - 03:48 AM

Extending the arms out and facing the strobes out for feather will provide two different results. The further out the strobes are from the lens will create more texture and depth in your image. I use 2 16" arms on each side and try to keep them out as far as possible and back behind the camera. Then I feather on top of that to skim the light across the surface of my subject creating more depth in the image. As ChrisRoss said, the closer the subject usually the closer your strobes come in and everything else he said is on point as well.


The easiest way to understand lighting in Wa is to use your flashlight while diving and try different methods and watch what happens with out a camera at all. I started photography in WA with nothing but a flashlight and the on camera flash turned down as low as possible to fill shadows. It helped learn how to reduce backscatter a great deal. On the next dive without a camera take the flashlight in your left hand since usually the camera is in the right. Extend your arm completely out with subject directly in front of you and light facing far left. Rotate the flashlight beam towards the subject to feather it. You'll see the sweet spot as the light just starts to illuminate the subject. Pretending your head and eyes are the camera and your flashlight is the strobe with your arm kept straight and move your arm forward and back like you're making snow angels and watch what happens. As your arm moves back you should see less backscatter. I prefer back and slightly up to give nice shadows and light. Now try doing the same thing with your arms tucked in closer with the light closer to your head and feather the subject. This will show you exactly what strobe position will do without any equipment needed and save you some money while making sure you get what you're looking for. I usually shoot wide and not very much macro but I've seen a lot of people have the strobes in tight and facing forward. For super close up macro this will provide a feather and looks pretty good when I've tried it. You can try this by holding your flashlight near your head facing straight forward, then swim closer to you subject like your head was the camera and watch the light. 


Start with one strobe and learn lighting and how to bring out texture then go to two strobes if you want. I've seen many people try to use two light sources when they don't even understand how to use one. I started with a flashlight, then one strobe, then two and now two on camera and 3-4 remote strobes in a cave. 

#4 simonunderwater



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Posted 31 March 2019 - 05:44 AM

For macro photography, strobes are the sole source of light. With longer focal lengths and shooting with small apertures (higher f/stops), very little, if any, ambient light gets to the sensor. The use of one or more strobes is what lights the subject. 


One strobe can be enough to properly expose a macro shot, assuming the subject is small enough and you are close enough. However, properly exposed does not always mean the lighting is pleasing. Often times one strobe results in harsh shadows and flat images. This can be remedied by the addition of a second strobe acting as fill-light. Additionally, using two strobes allows for more creative options. Hence, dual strobes are highly recommended for anyone who is looking to seriously improve their underwater photography (macro or otherwise).


It's important to realize that each subject can be lit in many different ways, and often times the creativity of the shot is in the creativity of the lighting.  A great example of this is backlighting. Back-lighting is useful to give subjects a sharp outline. Point the strobe almost straight toward the camera lens, but block it with the macro subject to achieve this effect. An optional second strobe can again be used as a light fill to give the subject some colour. Obviously, this is not always the right lighting technique as it creates a silhouette. 

#5 TimG


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Posted 31 March 2019 - 06:10 AM

Id suggest a third approach.

Find one element in the scene you intend to photograph - maybe a colourful bit of soft coral - and have that to one side of your image and close in. Light it with one or two strobes - on the same side. Then have a dive buddy on the other side of the image to create balance and expose for ambient light.

You can end up with a nicely balanced, composed image, with human interest (nice for context), great colours in the corals and, voilà, no backscatter.

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#6 adamhanlon


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Posted 31 March 2019 - 02:27 PM

Reducing backscatter in murky water is about controlling light and ensuring that the harsh, bright light that is close to the strobe does not illuminate any particles that are visible in the image.


The simplest way to do this (I find) is to keep my strobes pointing straight forward and simply pull them back (with an SLR or big housing) behind or in line with the handles. I start with them at handle height, and as I seek to illuminate subjects further away, simply lift them up. 


This can be done with relatively short arms.


Of course, if you are using high f stops with macro subjects, the strobes may well need to be moved forward toward the end of the port.



Adam Hanlon-underwater photographer and videographer
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