Fringeheads and Baby Seal Lobos Sunday April 6th dive

[Chuck Tribolet]

The diffusers will prevent the foreground from getting blown out only because they reduce the
amount of light. You can get the same effect by closing down the aperture 1 to 1.5 stops. The
intensity of light decreases as the square of the distance from the light source, so when you halve
the distance you have four times more light and need to close down two stops. Both diffuse
and specular light sources obey this square law.

And if you do want diffusers for the more diffuse source, the trick stuff to make them from is the
milky white plastic sold at TAP Plastics for making light boxes.

 

[DocWong]

Yes, they are external controls for Neutral Density Filters. Or at least that's what I think they are for from the manual.

 

[DocWong]

The diffusers will prevent the foreground from getting blown out only because they reduce the
amount of light. You can get the same effect by closing down the aperture 1 to 1.5 stops. The
intensity of light decreases as the square of the distance from the light source, so when you halve
the distance you have four times more light and need to close down two stops. Both diffuse
and specular light sources obey this square law.

And if you do want diffusers for the more diffuse source, the trick stuff to make them from is the
milky white plastic sold at TAP Plastics for making light boxes.

I don't think I'd want a diffuser on my lights as they would be too much trouble to remove and reinstall under water.

I found that the only time the lights are too bright is when it's on the white elephant ear sponges. Or something very white.

 

[limeyx]

Yes, they are external controls for Neutral Density Filters. Or at least that's what I think they are for from the manual.

I had ND on my cam too and never really use it (because it seems from the housing that I can only turn ND on but not off!)

I just spent 1/2 a dive with a 2-stop ND accidentally engaged, and had to dial the gain up to 12Db to be able to see anything but black.

 

[limeyx]

The diffusers will prevent the foreground from getting blown out only because they reduce the
amount of light. You can get the same effect by closing down the aperture 1 to 1.5 stops. The
intensity of light decreases as the square of the distance from the light source, so when you halve
the distance you have four times more light and need to close down two stops. Both diffuse
and specular light sources obey this square law.

And if you do want diffusers for the more diffuse source, the trick stuff to make them from is the
milky white plastic sold at TAP Plastics for making light boxes.

My (probably incorrect) understanding was that the more diffuse light would look less harsh oin the cloesup stuff, but I wouldnt lose much :"distance" with the lights.

But like I say, I am likely wrong

 

[DocWong]

I had ND on my cam too and never really use it (because it seems from the housing that I can only turn ND on but not off!)

I just spent 1/2 a dive with a 2-stop ND accidentally engaged, and had to dial the gain up to 12Db to be able to see anything but black.

That's weird, to not be able to control it the other way. On my housing for the VX2000, it's actually a manual switch that I can toggle from off, N1 and N2.

You sure you can't toggle back to "off" on the the ND (Neutral Density) control.

For those of you who don't know what ND is, it's a contol that filters out a certain amount of light.

 

[Chuck Tribolet]

Doc: It doesn't have an f/stop setting?


Chuck

 

[DocWong]

Doc: It doesn't have an f/stop setting?


Chuck

Yes, it does, both manual and automatic. I'm not sure of the relationship, but the N1 setting let's in 1/4th of the light and the N2 setting let's thru 1/32nd of the light. So perhaps the N1 and N2 settings are the gross amount settings and the F stops for fine tuning?

 

[opisthobranch]

Yes, it does, both manual and automatic. I'm not sure of the relationship, but the N1 setting let's in 1/4th of the light and the N2 setting let's thru 1/32nd of the light. So perhaps the N1 and N2 settings are the gross amount settings and the F stops for fine tuning?

Hi Doc,

I'd advise against using the ND controls in local waters except under very specific conditions. All they do is block light from entering the camera and with our visibility (ie lack of light) you never want that. I'd only use them if I was silhouetting a jellyfish against the sun in very shallow water. That might be necessary to avoid over-exposure shooting into the sun.

The aperture control should be sufficient to stop down enough to control the light against the sponges. Watch the zebra striping (unfortunately not viewable on the external monitor) to see what's getting blown out and dial down until there is only a minimum of striping on the display.

If the background looks to dark try shooting up rather than horizontally. Getting a balanced exposure with video is hard since the lights are on all the time rather than instantly like a flash so you can't use shutter speed to control the background. For local stuff I left the shutter fixed at 1/60th. Slower means the shutter is slower than the frame rate (well actually the field rate as every other line is 1/60th of a second). You can shoot with a faster shutter if necessary to reduce light but I never found a need locally. If you're in shallow water in the tropics you might want to shoot a faster shutter speed.

Clinton

 

[limeyx]

That's weird, to not be able to control it the other way. On my housing for the VX2000, it's actually a manual switch that I can toggle from off, N1 and N2.

You sure you can't toggle back to "off" on the the ND (Neutral Density) control.

For those of you who don't know what ND is, it's a contol that filters out a certain amount of light.

I think it's just a flaw in my housing, the little plastic twiddler thingy can go from off to ND1 to ND2, but I cannot make it move the switch the other way -- I may have broken something off on the arm.