Backscatter despite having a strobe

[Cosmographer]

I just returned from my very first dive with my own photo gear (Panny LX5, 10 Bar housing, YS-01) and noticed a significant amount of backscatter despite having an external strobe. The two pics below exhibit some of the worst backscatter I experienced, and hopefully, you can see from the shadows that the strobe was off to the side and slightly above the camera - not flashing straight forward.

Is this because I'm only using one 8 or 9 inch arm? The arm seems to get the strobe far enough away so that the light is hitting the subjects at an angle - is this not enough? I even tried to angle the strobe so that only the outer edges of the cone of light would illuminate the subjects as I learned from these forums. Not sure if that helped or not. Any advice on how to avoid this problem in the future would be much appreciated. (Yeah, I know these pics aren't focused either - one challenge at a time! )

 

[flareside]

Is this because I'm only using one 8 or 9 inch arm?

Yup. The greater angle between the strobe and the lens, the less noticeable it will be. Distance to the subject also has an impact so keep as little water between you and the subject as possible.

 

[Cosmographer]

Thanks, Flareside. But even with a short arm, you can see the shadows that are clearly cast by the light. Wouldn't moving the strobe out further just exaggerate this effect even more, effectively lighting just one side of the subject?

 

[buton]

Maybe you are shooting to far and the camera is taking that light from the side..

 

[Larry C]

Sometimes backscatter is pretty much unavoidable. In the Lionfish picture, it looks like the water was quite silted up. This happens from fin kicks, etc. that lift the sand off the bottom. It also happens when the subject makes a quick move and stirs up sand. If the sand is in the lighted part of the shot, you will have backscatter, because some of it will reflect back. The trick is to aim your strobe so that the outer edge of your light is on your subject and the rest is behind the subject or out of the frame. This will minimize backscatter, but if you silt up the water or the subject does, you have to wait for the silt to settle before you shoot.

 

[HowardE]

With a single strobe, people are more apt to have backscatter (than with dual strobes), as the tendency is to light up the subject directly with the strobe. This frequently causes backscatter, and as you can see from your images... shadows.

When you have 2 strobes, you can light up the frame without directly lighting up the subject, and this generally makes for less backscatter, even in somewhat silty conditions. Generally speaking, you keep the strobes pointed straight ahead, having only the inside edge of the light merge on the subject. This greatly reduces backscatter.

 

[Cosmographer]

I was afraid of getting the "2 strobes are better" explanation, lol. Not sure I can get my wife to approve another expenditure! I was hoping I just needed an extra arm to get more distance, but it makes sense that with 2 strobes, your light source can be far off to the side while still eliminating shadows.

Indeed, the water was quite silted up in both those pics, but I guess I was just hoping the strobe would perform some kind of magic, hehe.

 

[DazedAndConfuzed]

get some looong arm and have the strobe be as off-angle from the lens as possible. I've had picture of silts or paritcles in front of the subject but not backscatter back to the camera because the strobe was so offset from the camera. Although they are still visible, just not prominently lit.