Why the lights of that photo are too much blue/white in the edges?

Question

yesterday I was taking some pictures from my city during the night and I could not find an explanation regarding the strange edge of blue/white lights.

I have the RAW file of it and I've tried to change the exposure of those lights but it did not fix the look of the lights.

I will appreciate any help.

Answer 1

1. The reason of those flares to appear is optical diffusion and internal refraction which is almost fine with normally observed objects but is obvious if the object is a bright spot light source - it affects all objects equally but it is only visible on high contrast transitions.
2. The reason of them being asymmetrical is coma.
3. The reason of them being coloured is longtitudinal chromatic aberration which results from dispersion.
4. The reason for them to look so terrible is aggressive profiling which needs to be done to bring the image data recorded by camera closer to the reality (the bad form of colour sensing to be specific), and it's imperfection is exceptionally obvious with saturated objects. This is very apparent in photos of recent Canon DSLRs because they tend to require strong profiling.

Here are two verions from same file, one from Adobe Camera RAW and one from RawTherapee with custom weaker (less saturated) colour profile.

There is a way of making saturated bright sources look good - give tonal curve a wide shoulder and it will look natural. (your tonal curve will be different from the one displayed, experiment to find the one which you need)

Related.

Answer 2

What you're seeing is called coma.

Some lenses are considered better than others at dealing with coma.

It can sometimes be reduced by stopping down your lens a couple of stops from wide open, although this can be a difficult trade-off for night scenes or astro-photography.