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Why is the afterburner flame of some fighter aircraft blue while for some it is orange?

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    $\begingroup$ Nothing more than photography and ambient light (disregarding "exotic" fuels and designs). Take a look at these images of Phantoms in reheat. Sometimes it's yellow, sometimes it's white. $\endgroup$ – Simon May 27 '16 at 10:51
  • $\begingroup$ I am looking for the engine and fuel aspects, lighting and ambient lights make a very minuscule difference. $\endgroup$ – Adder May 27 '16 at 12:08
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    $\begingroup$ "lighting and ambient lights make a very minuscule difference". On what do you base this statement? Take two identical aircraft. At night, the reheat plume appears more white. During the day, it appears more yellow. Since they are identical, I can think of no other reason. It's certainly the case with Phantoms, on which I worked for 4 years. You can clearly see this in the images I linked. Here are some more examples. $\endgroup$ – Simon May 27 '16 at 12:23
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    $\begingroup$ Please post the sources of your images $\endgroup$ – FreeMan May 27 '16 at 12:39
  • $\begingroup$ I took the time to find some very representative images. Compare this one with this one. Same engine, same fuel. $\endgroup$ – Simon May 27 '16 at 12:41
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I agree with Simon's comments. Lighting and ambient lights make all the difference.

The flame is always equally bright, so if the ambient light is lower, the difference between the flame and the rest of the image is larger. When the difference exceeds the dynamic range of the film or sensor, the image of the flame becomes saturated in all channels and ends up as white. Note, that all the images with white flame are night ones.

Also the blue sensor is slightly sensitive to near infrared (being about half wavelength of the blue light), so when high sensitivity/long time are used, this causes the blue glow around the white flames on night images, while on day images with lower sensitivity it is not noticeable.

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    $\begingroup$ About the sensor: they are all sensitive to IR, and its a common practice to use a camera to check an IR remote control. If it's working, the LED flashes blueish white like the exhaust flames in the picture. Also, cigarettes and glowing coal appears in this color. So yes, hot glowing stuff often appears blueish white on photos. But many better cameras have an IR filter and give a more realistic picture. $\endgroup$ – sweber May 27 '16 at 14:44
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    $\begingroup$ If anyone has any doubt about Jan's answer, go ask at Photo.SE, they'll give you more detail than you could ever want. $\endgroup$ – FreeMan May 27 '16 at 15:48

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