Sodium Street lighting - Filter?

I just found this ...

Photoshop:Neutralizing Color Casts With The Photo Filter

Sodium light is, or seems to be, more of a colour cast than a colour temperature. I shall give it a go

I believe a correction filter change the temperature of the sodium light to daylight so it won't block that colour but I can be wrong with that.

Well it has no use on digital because it always capture red, green & blue and the white balance simply change the balance between the three colours.
A correction filter will also shift the balance but since you can already do that it does not add any real value.
You might shift the colours so that the scene is spread over all the three the colours so that your sharpness improve but that's the only thing I can think of.

The tutorial you've there is the digital equivalent what such filter would do

The problem is that Sodium discharge lamps don't produce a spectrum which looks even remotely like a 'white hot' body. Hence the 'colour temperature' doesn't really exist. The spectrum is not continuous so Sodium light (even high pressure versions) will never give the true colour of some objects because the light just doesn't exist at the wavelengths they reflect. Once the camera has analysed the light it receives into three channels, the damage has been done. All you can hope for is to use your image processor to produce an effect that is 'least displeasing' or 'least inaccurate' for a particular subject.

Hiya

Indeed I'm not loking for accuracy but something that looks nice without the nasty orange cast.

I had some interesting results trying the remove colour cast technique in PS. I'll post a couple of exmaples soon.

Looks like we need a mod

Yes - the same 'spam' is appearing on other posts

Sorted.....

As Stefan says, the light from a low pressure sodium lamp is not a continuous spectrum. It consists primarily of two closely spaced yellow spectral lines. These lamps are often used in physics labs, as they provide the nearest thing available to a monochromatic light source. See this Wiki about sodium lamps

You simply cannot filter out the yellow/orange light - because that's pretty much all there is.

Andrew

Exactly. That's why a colour temperature filter wouldn't work and one would need a proper filter like the Singh-Ray Lucalox job I linked to in the first page of the thread. i.e a notch filter rather than broadband filter. I was trying to think of ways to notch out certain a single light frequency ( treating the closely spaced freqs as one for all practical purposes ). It turns out the colour cast removal method in Photoshop (linked above) works quite well. Indeed the inverse colour looks pretty much the same colour as the Singh Ray Lucalox filter.

And yup you're right, if the sodium lamp is the only light source then you're not really left with anything once it is filtered out. Fortunately many scenes have other sources of light. Here's a couple of test examples I did in photoshop ... I took a pic of a sodium lamp outside my house in order to grab the colour.

It's subjective as to which version looks the best, but I did these with 100% reduction, so you could simply use the technique to reduce the amount of orange. No need to buy a filter now. PS works with all lenses

Who not so fast

yes that's very correct

Singh-Ray Lucalox is a colour temperature filter like what you can read for my earlier posts.

Here is a read about colours with photography link

I've looked it up what the colour temperature that you need.
High-pressure sodium light 2100 Kelvin

The K7 will probably be able to read this right in automatic white balance since it does well with tungsten but the older models have more problem there.

I've done this with the white balance inside lightroom 2, does it come close?
[IMG]http://i282.photobucket.com/albums/kk244/Anvh/2010-01-09_4584_sodium_filter_test-.jpg[/IMG]

If you've a RAW you can do it better.
here is a little test of mine.
[IMG]http://i282.photobucket.com/albums/kk244/Anvh/_IGP9050.jpg[/IMG]
[IMG]http://i282.photobucket.com/albums/kk244/Anvh/_IGP9050-2.jpg[/IMG]

Have I now convince you it's colour temperature?

I can see what you're saying

but Sophiecentaur's post here also made some sense ....

I tried applying a 2100k setting to a few of the RAWs from the same shoot and while the Pub above looks OK many of the shots have a washed out Blue colour cast at 2100k.

I'll do some more tests and compare changing colour temp to the remove colour cast method.

I do appreciate your input to the thread

yes it does and it is correct but light is difficult to understand.
I can see where you're coming from since it's such a narrow band but in what way does the light source differ from each other?

Al you try to do with white balance is trying to make white, white and that's exactly what you want right?
So the Yellow sodium light is filtered out/shifted so that you get white.
I think we are talking about the same thing here but seeing it differently

About the 2100k, I've tried that as well and indeed it's to blue.
With the shot of mine I took the white balance from the roundabout traffic sign and it meters.
colour temperature of 3450k
and a tint of +50 magenta

Also there is a big difference in high and low pressure sodium lights
here read this, the smal part about sodium light at the end link

Looking back to the original thought, which I think was that the OP did not like the appearance of sodium lighting, but did like the alternatives that are sometimes used.

Soium lighting is used as I understand it because it's relatively unobtrusive and encourages the eyes to open (good for night driving) and not to close down. The worst thing about it IMHO is that as soon as it rains all the road markings virtually disappear.

I've seen different lighting in Chipping Sodbury some years ago, and those were mercury vapour lamps I think. Very blue, quite another problem.

However, the scene is the scene, so it's only within certain limits that we can change it. I would suggest trying for dusk or dawn, probably the former, when people start to turn on their lights but maybe the sodium lights are only just coming on. A mix of slightly more natural light and some building lights might be a lot easier to correct.

In addition, many night shots benefit from having some light left in the sky.

John I've also heard about the blue lights, it appear that our eyes are pretty good with blue light and keep us awake, our biological clock runs on blue light.

Also animals, namely birds, have less of a problem with the blue light.
Sometimes they get lost with the yellow lights of the street lamps.

That was all heard on a radio program, so don't know if you can find something on the web about it.

The main reason why low pressure sodium lamps are used for street lighting is because it is the most efficient light source - i.e. you get more lumens per watt, so they are cheaper to install and run. Most things boil down to economics in the end.


Andrew