Reducing Backscatter

[meathead_dave]

I was diving in the NDAC yesterday and took a load of piccies using a Sea & Sea DX-1G with a YS-27 strobe on a flexible arm(about 16" in length). The vis was sh!t - less than 5m. Virtually all pics taken have a shedload of backscatter on them. I previewed them underwater and tried moving the strobe around but to no avail. Whatever I took there was a lot of snow on them. Obiovusly this is due to all the detritus in the water but I was hoping having just moved to a strobe to avoid the majority of problems with backscatter. Would a longer arm help, or is the strobe not cranked enough ( howwever I did get some over exposed shots when I did turn the power up). Or is it a case of needing a wide angle lens and getting closer so the angle of the strobe is more from the side. The macro shot tended to be ok which leads me to think that the problem is with the distance. Any advice VERY gratefully received. I have only used the set up twice in water so I appreciate I am still on a massive learning curve!

[Cussy]

The answer is depends.

If the water is FULL of crap, then no matter how long your arms are you will have back scatter. There are a number of things you can do though. One common mistake I make is have my strobe too far forward, so the hotspot created by the strobe gets in view of my photo (admittadely I am using a fisheye). Another common mistake is to point the strobe at what I want to illuminate. What you need to do is catch the subject with the edge of the light. If the strobe is away from lens on arms and you use edge illumination then nothing between you and the subject is illuminated to give back scatter.

Changing f number has a big effect on how well you can see backscatter too. Martin Edge covers this really well in his book - actually he covers everything about flash really well. Shooting manual helps, once you know what the setting will do you will have control. When I got my first camera (a second hand Nikonos 4) then any backscatter would kill a shot, you could only shoot in clear water. I found similar results with my first Olympus and YS-25. Take control of everything and it works - honest.

So don't immediately think you need longer arms. If you are in a club then take the camera into the pool as much as you can. Pools are bloody difficult to illuminate and you can quickly learn what to do.
HTH,
Rob

[Okeanos]

I think Rob's covered most of it there. If there is a lot of stuff in the water it will always make it harder to get a half decent wide angle shot.

[Richard Mason]

Originally Posted by meathead_dave

I was diving in the NDAC yesterday and took a load of piccies using a Sea & Sea DX-1G with a YS-27 strobe on a flexible arm(about 16" in length). The vis was sh!t - less than 5m. Virtually all pics taken have a shedload of backscatter on them. I previewed them underwater and tried moving the strobe around but to no avail. Whatever I took there was a lot of snow on them. Obiovusly this is due to all the detritus in the water but I was hoping having just moved to a strobe to avoid the majority of problems with backscatter. Would a longer arm help, or is the strobe not cranked enough ( howwever I did get some over exposed shots when I did turn the power up). Or is it a case of needing a wide angle lens and getting closer so the angle of the strobe is more from the side. The macro shot tended to be ok which leads me to think that the problem is with the distance. Any advice VERY gratefully received. I have only used the set up twice in water so I appreciate I am still on a massive learning curve!

It could well be back scattering due to stray light emissions from the built in flash that triggers the strobe. I have a DX850G & same srtrobe and I had terrible problems with this; the diffuser built into the housing is about as much use as tits on a bull.

I found that blacking out the front of the housing with black tape reduced the problem by about 95%. All my poics had this problem.



I've since put more on, around the lower edge of the housing. I'm seriously considering carefully painting the inside of the housing to make it a permanent fix.

This was the result:

Before




After (in poorer vis)

[Beeblebum]

Much of what needs to be said, has been. Though one other thing comes to mind. Were you using the diffuser? The diffuser widens and softens the stobe beam making the 'edge' less distinct. When 'edge' lighting with particulates in the water it's probably better not to use the diffuser.

[meathead_dave]

Yeah, i had the diffuser on the strobe. thanks for your replies chaps - I will try it all out next time I'm in the water - this thursday on a night dive at Vobster - can it get any better in december?