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Topic: First photo with Strobe (Read 2772 times)
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gary ramey
Barracuda
 Offline
Aurora Colorado
Posts: 681
my transmogrifier isn't working
 
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Re:First photo with Strobe
« Reply #2 on: August 09, 2009, 01:02:05 AM »
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Photos like this have great color, but lots of 'artifacts' that I would like to be able to avoid.
Is this backscatter ?, Marine Snow ? |
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The holographic circles are backscatter. The ones that have a geometric shape to them are actually tiny bubbles/particles either on your port or very near (that hexagonal look is actually the same shape as your aperture blades). Finally, the particles lit up by the strobe are marine snow, sand, silt or sediment. Welcome to underwater flash photography!
Back Scatter is caused when you light up a particle directly with the strobe and it reflects directly back into the lens. The other two causes are understood. I usually fan the port on my housing with my finger tips to make sure I'm don't have any bubbles on the port. You have to live with the viz that you get..ie sediment or snow.
To reduce (ie we sometimes have to live with some) of these problems you can position your strobe farther away from your port. If the water is really snowy, you can pull the strobe behind the port, extend it out as far as you can from the port and angle it slightly out. The edge of the strobe should light should "feather" your subject. You'll have to set the strobe to manual because chances are s-ttl will leave it underexposed if you do it this way. Finally, the best way is to get closer. Sometimes we have no choice because of the viz and we simply fill the frame with the subject.
Finally, I seem to have all the answers but the truth is I struggle in this area too. Its really tough to hit a subject with a strobe that angled out and at the same time get the exposure right. If you can bracket and shoot RAW that helps too.
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Gary
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Canuck
Great White
Offline
Lethbridge, Alberta, Canada
Posts: 3544
jelly jelly
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Re:First photo with Strobe
« Reply #4 on: August 09, 2009, 11:02:42 AM »
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I am using the strobe without cables,
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If I am reading this right, it sounds to me like you are not using an optical sync cable, but rather simply using the strobe as a slave. If so, this is likely a large part of your problem. Your internal strobe is firing directly at the particles, causing much of the snow. We use a strobe and place it off axis as far away from the port as possible to reduce backscatter. The reflected light from the particles bounces back towards the strobe, not the camera, for the most part, and therefore does not show up as much in the photo. You would be much better off if you covered the internal flash and used an optical cable to sync your strobe.
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John Davies
my website
Canon 40D, Subal housing, Inon strobes, Tokina 10-17 mm FE, Canon 60 mm macro
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