Herman Surkis
Posts: 6,219
Victoria, British Columbia, Canada
Friend was shooting with Einsteins.
One was a back light, gelled with yellow, and shooting through the fog from a fog machine.
Fog has a greenish tinge, which actually for his image it is better.
But why would a Yellow gel create a green fog?
Chemicals in the goop?
Colour balance of the Einsteins and his camera?
The light on the subject was fine. But that was from the other Einsteins.
Could the other Einsteins have added a blue cast to the fog, which when you add the yellow gel made the effect green?
But your theory of the einsteins going blue sounds reasonable IF
A) the backlights had their power turned way down AND
B) the light was set for speed not color
WMcK
Posts: 5,182
Glasgow, Scotland, United Kingdom
Xenon tubes do not emit a continuous spectrum, it has gaps in it. What the eye sees with modelling lights is not guaranteed to be the same as the camera sees with xenon flash.
I have seen something almost identical happening with yellow gelled HMI lighting and video cameras. The fog (meant to look like chlorine gas) looked yellow to the eye but green to the cameras.
Also the particulate nature of fog can give odd colour shifts which can contribute to the effect.
Kaouthia
Posts: 3,080
Lancaster, England, United Kingdom
Herman Surkis wrote: Colour balance of the Einsteins and his camera?
That would be my thought. I'd do a pre-set white balance with the flashes without any gels, and then add the gels and get shooting.
Not all flashes are created equally, and their temperature can shift a little over time as the bulbs age, or at different power levels, and it can change depending on what modifiers are being used. So, I always get a custom white balance when using flashes or modifiers I've not used before.
Herman Surkis
Posts: 6,219
Victoria, British Columbia, Canada
WMcK wrote: Xenon tubes do not emit a continuous spectrum, it has gaps in it. What the eye sees with modelling lights is not guaranteed to be the same as the camera sees with xenon flash.
I have seen something almost identical happening with yellow gelled HMI lighting and video cameras. The fog (meant to look like chlorine gas) looked yellow to the eye but green to the cameras.
Also the particulate nature of fog can give odd colour shifts which can contribute to the effect.
At the moment this is where I would put my money.
The effect is cool, but ...
I do not like not knowing why some thing unexpected happened. Next time it happens I want it to be because that is what I wanted. Not my shoot so I cannot post the images.
Where the light is, directly behind the subject it is blown out as expected.
The upper 2/3 of the fog is greenish. The bottom 1/3 of the fog, and the floor has a yellow cast to it.
Background is black, as it is supposed to be.
The 2 side lights are ungelled and feathered away from the fog.
Fill light (front) is ungelled.
Herman Surkis
Posts: 6,219
Victoria, British Columbia, Canada
Kaouthia wrote:
That would be my thought. I'd do a pre-set white balance with the flashes without any gels, and then add the gels and get shooting.
Not all flashes are created equally, and their temperature can shift a little over time as the bulbs age, or at different power levels, and it can change depending on what modifiers are being used. So, I always get a custom white balance when using flashes or modifiers I've not used before.
These are Einsteins that are relatively new. Like 6 months old.
WMcK wrote: Xenon tubes do not emit a continuous spectrum, it has gaps in it. What the eye sees with modelling lights is not guaranteed to be the same as the camera sees with xenon flash.
I have seen something almost identical happening with yellow gelled HMI lighting and video cameras. The fog (meant to look like chlorine gas) looked yellow to the eye but green to the cameras.
Also the particulate nature of fog can give odd colour shifts which can contribute to the effect.
So here is the absorption chart for a yellow filter
I'm no expert, but there doesn't seem like a lot of yellow coming out of the flash and the blue is being blocked by the filter, And that leaves a bunch of green.
WMcK wrote: Xenon tubes do not emit a continuous spectrum, it has gaps in it. What the eye sees with modelling lights is not guaranteed to be the same as the camera sees with xenon flash.
I have seen something almost identical happening with yellow gelled HMI lighting and video cameras. The fog (meant to look like chlorine gas) looked yellow to the eye but green to the cameras.
Also the particulate nature of fog can give odd colour shifts which can contribute to the effect.
I'm not sure if this is part of what you're saying, but we see color based on waht's reflected. So yellow light may go in to the fog which may not reflect in a balanced way so that more blue comes out, or more likely less red.
WMcK
Posts: 5,182
Glasgow, Scotland, United Kingdom
MC Photo wrote: I'm not sure if this is part of what you're saying, but we see color based on waht's reflected. So yellow light may go in to the fog which may not reflect in a balanced way so that more blue comes out, or more likely less red.
Yes, that's more or less it. And sensors can sometimes see these colours a bit different from the eye.
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