Thursday, April 21, 2011

Sodium Vapor

I discovered something new today.  It came to me because I was retouching an image that happened to only be illuminated by one high pressure sodium vapor light directly in front of the building.

Have you ever shot sodium vapor and tried to correct for it?  I have but not to this extent.  What do you do when you don't know anything about sodium vapor lights?  Google it.

I came across a forum on or something of the sort that pointed me in the right direction to correct my white balance.  Well not particularly, but it did give me the idea to play with the RAW files in Adobe Camera Raw and use the HSL/Grayscale section.

In order to even get started with correction, I had to know what colors sodium vapor produces when it is fully warmed up, and that is where the forum came in.  I knew Sodium Vapor was orange, but didn't know the light has a hell of a lot of yellow.

After a couple of different techniques in ACR to get the orange/yellow out, I finally figured it out.  Reading that SV lights are around 2100-2700K a very cool light temperature almost approaching that of a candle flame.  2700K looks disgusting so I decided to jump up to 3350K, why?  Because it looked the best.  Color temperature in ACR can only correct for 4 colors, blue, yellow, green, and magenta.  What it doesn't do is only take out yellow and keep blue.

This is the magical part of my 3 hour retouching adventure.  Take 3350K one step further and desaturate under the HSL section, all the yellow, and for my situation -30 orange.  That was only the beginning as there was still a ton of orange on the asphalt, which I used just a simple HS layer and desaturated and masked back in the parking lot.

Thank goodness for the Internet enabling me to search for sodium vapor light color correction and the knowledge I gained from spending 3 hours in front of a computer, blending, retouching, color correcting, and more retouching.

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