Background Colour Correction

[Somerled7]

I recently bought an Astronomik clip-in CLS filter, so now instead of a pink sky I get a turquoise one.  I can get longer exposures before the background sky dominates, but I'm still left with a major colour correction to do, as shown in the attached image.  So any advice on the best way to do thus in Photoshop?  I've been using a Levels adjustment, shifting the black level on each colour channel up to the bottom of the histogram peak, but I've also seen it suggested to use a white balance correction (which I've tried, but that gives quite a muddy image), or create a custom white balance by photographing a white card.  Any advice welcome.   

[geordie85]

The easiest way is what you're already doing. Even with mono imaging, you still need to align the histogram of all 3 channels 

[steppenwolf]

My preferred method here is adjust the three colours separately in 'Levels' while referencing the 'all colours' Histogram until the colours all 'stack' one on top of the other and then adjust the whole RGB image until you get a background with measured values (use the 'Curves' tool and a pipette with a 3 x 3 size for the measuring bUT NOT the adjustment) of between 22 and 24 to ensure that you don't clip the black point and to give a natural sky intensity. I have found that this works very well.

[ollypenrice]

2 minutes ago, steppenwolf said:

My preferred method here is adjust the three colours separately in 'Levels' while referencing the 'all colours' Histogram until the colours all 'stack' one on top of the other and then adjust the whole RGB image until you get a background with measured values (use the 'Curves' tool and a pipette with a 3 x 3 size for the measuring bUT NOT the adjustment) of between 22 and 24 to ensure that you don't clip the black point and to give a natural sky intensity. I have found that this works very well.

I was about to say something so similar as not to be worth the distinction.

Olly

[steppenwolf]

2 minutes ago, ollypenrice said:

I was about to say something so similar as not to be worth the distinction.

Olly

I guess that means that it MUST be the correct method then!! 😎 I bet, however, that you wouldn't have spelt 'BUT' with a lower case 'b' as I did! 😱🤣

[ollypenrice]

2 minutes ago, steppenwolf said:

I guess that means that it MUST be the correct method then!! 😎 I bet, however, that you wouldn't have spelt 'BUT' with a lower case 'b' as I did! 😱🤣

🤣  Hey, I do all this in PI nowadays, before fleeing to the sanity of Photoshop. But I used to do it pretty much as you descirbe.

I make a point of not commenting on peoples's buts on SGL: I certainly don't want them commenting on mine!

Olly

[Somerled7]

Thanks guys. Sounds like I'm doing it about right, but having a specific target for the blacks is useful to know.