Riddle me this one

[Sprint]

Camera: In-phone camera - Nokia E51

Photo was taken after a burnout event where the vehicles back brakes had caught fire, fire was extinguished with a dry powder fire extinguisher, I took the photo and only noticed later the really strange colour of the rear rotors...

Photo has not been edited further than resizing it for the forum, and the rotor was glowing orange


What wouldve caused the change in colour from a bright orange glow to the colour you see?

[Jojo]

No filter? Sodium-vapour lamp close by???

[theresanothersteve]

Would depend on the chemical used in the fire extinguisher. Motorsport sometimes uses a different compound than regular dry chem.

I would guess you are seeing the results of a chemical reaction, same as if you sprinkle various substances in a fire. The heat from the disc is causing a change of state from solid to gas, your photo has captured the gas/ vapour.

[Bushie]

Possibility the residual powder from the extinguisher was acting as some kind of filter ? They tend to be based around sodium/potassium salts.
Who knows what happens when different chemicals get heated/subject to fire.

Martyn

[bobslandies]

Different elements give off colours (some not visible to the eye) when significantly heated. Sodium is yellow, Potassium is lavender. Fire extinguisher powder is broken down in the fire and generally gives off carbon dioxide to smother the fire.

Here is an likely explanation:

Flame Emission Spectroscopy (http://www.science-projects.com/fes/FlameEmissions.htm)

Bob

[vnx205]

If the change in colour is only in the photo rather than the rotors actually changing colour, it could have something to with an auto white balance setting if the device used to take the photo has such a feature.

If there is an extraordinary amount of red in the photo, the auto while balance will try to reduce the red until it gets what it considers a normal amount of red overall. Those intense red tail lights might have fooled the white balance.

If that is what happened, then given the the colour of other objects in the photo, you might not have noticed.

However, the ground under the car looks a bit green. Was it really? If not, then the auto white balance adjustment might be the answer.

[werdan]

Camera sensors are sensitive to infra-red light. Cheaper cameras that they put in phones don't have the filtering that more expensive cameras do.
The brake discs look like they are putting off a bit of infra-red as well as orange.

Try taking a photo of a TV remote LED while you are pressing down a button. You should find the LED is glowing purple too.

[stallie]

My votes on the white balance adjustment.

Open whatever image processor you use and change the WB to show the coloured of the rotors as you recall them.

See if thee other colours inte pic are then as u remember them.

[werdan]

Here's a link showing what I'm referring to.

Invisible Light (http://light.sci-toys.com/book/export/html/5)

And another showing the element of an electric stove as purple for the same reason..

http://supernovacondensate.net/2009/06/02/infrared-cameras-for-the-masses/