Arm lengths for very wide angle cave-floor pictures?

[Aotus]

I am shooting a panasonic lx10 with nauticam wide angle wet lens, using two sea&sea YS-D1 strobes, shooting the floor of a cave from 5-10 feet above (depending on how well these strobes light it up). Flat, even lighting is critical for my data collection. I've been reading about strobe position. It seems like most people prefer a 6" and an 8" arm, but I was thinking that longer arms would be better for my application, maybe 12", or 1 12 and 1 16? I have some unbranded 8" float arms, so the cheapest way to go would be only one set of new arms, maybe 16, but 16 would probably be very cumbersome without a pair of 12s to help them fold up into a tighter package for transport (without breaking it down).

I'm grateful for any thoughts.

 

[tursiops]

The arm length desired is really dependent on the camera-subject distance, and the water clarity, in addition to artistic factors like shadows. In most open water, you want as little backscatter as possible, so want to keep the arms out where you can get maybe a 45 deg angle for the light to hit the subject (90 deg would mean the light is beside the lens). Thus, you see enormous arms beside dome ports as people try and mitigate backscatter

If your water is really clear, as I expect you will have, you can tolerate shorter arms. After all, if the subject is 5 ft away, then having an arm sticking out the side 5 ft (to get 45 deg) is just a bit awkward! I think the main reason people use short arms is for out-of-water carrying convenience, not for lighting for wide-angle.....short is nice for macro, of course.

 

[Aotus]

thanks for the comment. The water is very clear, though it would probably be a good thing to have some option to deal with it if there is some debris. That pic shows a single arm on either side, but I figured I would use a pair on each side, mostly so that it's collapsible, but also to give me options. maybe 12" and my 8" floaters would be ok...

 

[tursiops]

That was the first picture i found. Her are multiple arms. I've sen up to four on each side.

 

[Aotus]

four seems like a major hassle, but what do i know, i'm totally new to photography much less underwater shooting.

 

[tursiops]

I find two on each side enough of a hassle. With my WWL-1 I've used 2x8" on each side, and 8"+10" on each side. Some have been float arms, some have been arms with foam STIX floats, some have been naked. 4 years and I'm still playing with it. Never taken a picture of the floor of a cave, however.

 

[Aotus]

Never taken a picture of the floor of a cave, however.

I won't lie, it's not the most exciting part of the work.

 

[Laurie S.]

I use a combination of 8 and 12 inch arms when shooting my Tokina 10-17 mm fisheye lens, and 8 and 5 inch arms when shooting macro, which is what I do most of the time.

 

[jmartel]

Start with a 12" and 8" on each side. If you're getting too much scatter, then angle your strobes away a bit instead of straight forward. From that far away, you shouldn't have too many hot spots.

 

[Aotus]

thanks for the comments. I am currently leaning toward getting a set of 12" to pair with my 8" float arms, however I am thinking about whether I really NEED two-part arms, and now considering getting one pair of 16" arms and using them alone... I'm grateful for any additional thoughts.

cheers.