Flare and Backscatter!!!!!

OK, I'm still shooting film so by the time I see my pictures I can't remember what I did, but I'm hoping somebody here can help.

Problem 1: Flare with 50mm macro, Ikelite flat port, Ike 150 and 50ms stobes (though I've gotten the same problem with just one strobe)

Crinoid

The main problem is the white arc in the upper left. I suspect that some light is coming in through the barrel of the port (since it's clear) and bouncing around inside. What do you think?

Problem 2: Backscatter with 20mm, Ikelite dome port, 150 strobe

Diver and crinoid

My strobe is generally to the upper left and slightly in front of the camera. Is there an optimal angle to avoid backscatter?

Cool! I've gone through the same problems and I think I can help.

On the flare photo - yes, light is getting into your port. It could be because you have the strobe in front of the port and some strobe light is getting in, or it could be ambient light getting into the port.

Solution: Position your strobe behind the port or if it needs to be in front, make sure it is not pointing toward the port too much. Most importantly wrap the clear part of the port w/ electrical tape, but make sure you can still see the o-ring.

Second photo - backscatter. This is caused purely by strobe placement and aiming.

Solution: For wideangle, with a strobe like the 150 with wide coverage, position the strobe slightly behind the plane of your camera and point it straight forward. If you need to angle it in, then you will want a long strobe arm. A long strobe arm helps a LOT.

HTH

James

Thanks James.

Why does a long strobe arm help? Is the idea to get the strobe closer to the subject or further from the lens or both?

Further from the lens.

Think of it this way - the strobe throws a "cone" of light. In order to get backscatter, the light has to go from your strobe, to the particles, then to the lens.

Try doing some little doodle drawings with the strobe in different positions and pointed straight ahead and pointed in. Remember that the angle of incidence = angle of reflection.

You will see that with the strobe farther out to the side (say out on the left) that it will illuminate particles, but the light bounces off of them and ends up hitting over to the right of the lens. That is good.

Cheers

James

I'm not familiar with Ilelite dome ports, but if you have a port shield, it would help the flare problem to always have the shield mounted. The shield also helps protect the port surface.

Hello,

I have the same problem with my setup when shooting with the 20mm.

CANON EOS 30 in UKGermany housing with Subtronics Alpha Pro strobe.

I have ordered yesterday a 30cm element to add to my arms.

Will be 80cm away from the lens. Should be enough ?

Regards

Stéphane

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