A colour cast can be defined as an overbearing tint towards one particular colour, it’s usually an unwanted effect caused by certain lighting conditions such as incandescent or fluorescent lighting. Many cameras can control these colour tints by setting the white balance but there’s always the risk of not getting things the way you want in real-time and having to adjust it in post-processing. Thankfully, if you like working with Photoshop and Lightroom, that’s not a problem.
The real world is often different to how our eyes see it. In many circumstances a colour cast is a true reflection of the scene, it’s just our brain and eyes are good at adjusting and correcting the colours before we see them. Naturally we’ll want the photograph to look like the picture we see in our head, and that’s why the emphasis in this article isn’t on what the final image should look like, but the process of identifying exactly what colour makes up the cast. Luckily I’ve also got a couple of videos I’ll point out later on that go through that exact process.
So first and foremost, what’s a colour cast? Well here’s an example. The image below is one I shot myself on Clearwater Beach, Florida about thirty minutes before sunset. On the left is the original image with the camera set to auto. On the right is the adjusted version. The image on the left reflects the way the sand actually looked (or at least a similar version of it), whilst the image on the right is closer to how it looked to me on the day.
Now in this case the original image quite clearly has a blue cast, in fact I’ve used this example to keep things simple, however, quite often things won’t be as obvious as this and before you take it into Levels or Curves to make the necessary changes it may be helpful to get a better idea of what kind of cast you’re about to do battle with. This, my friends, is what we’re here for.
Open up the image you want to work with, or click here to download the sample file I’m using. First of all we’ll want to copy the image to a new layer by going to Layer > New > Layer via Copy (CTRL J on the PC, CMD J on the Mac). Rename the layer you’ve just created something meaningful like ‘Cast Identifier’.
Now we start to get clever. We want to find the predominant colour that exists in the image and we can do that by using the Average filter. Go to Filter > Blur > Average to apply it.And that’s it, we now have an accurate representation of the colour cast to take into Levels or Curves, or other commands such as Variations or Colour Balance. I’ve got a few helpful links to share with you, mainly taken from my 5 hour Level-thon that just happens to be freely available here at 3photoshop.com, and then I’ll show you how to take this technique further to actually correct the colours in this photograph.
First of all though, if you want to lift and evaluate the colour of the cast from this point onwards you can use the simple but highly efficient Eyedropper Tool. Fortunately I have a video tutorial devoted to the topic.
If you’re happy to take the photograph into another command and make the changes from there then you may find this tutorial on improving skin tones using CMYK colour values to be helpful. Once you’ve identified the colour of the cast it’ll help you to know how the big ole colour wheel works inside Photoshop to find the colours opposite. To find out more, and pick up a few tips and tricks on the improving skin tones, check out the video.
Finally, if you want to see how I’d tackle a colour cast in Levels using channel-by-channel modifications then check out this video – Levels: Removing a Colour Cast.
Alright, if you’re still with me, here’s how we can make some suitable adjustments to improve the colours in the Clearwater Sand image. We’ve already duplicated the original layer and applied the Average filter, here’s how we can use the resulting block of colour to produce a more balanced photograph.
If you took the time to watch the CMYK Skin Tones tutorial mentioned above then you’ll have a good understanding of how the colour wheel works in Photoshop. What we need to do now is find the ‘opposite’ colour to the cast, a feat that can be achieved by using another simple but highly effective command – Invert. To apply it, go to Image > Adjustments > Invert (CTRL I on the PC, CMD I on the Mac). We now have the colour we want to subtract from the image.What we need now is a way of keeping the luminance levels of the original layer but using the hue and saturation of the averaged layer – something we can do very easily by changing the blend mode of the averaged layer to ‘colour’. We’ve now got the complete opposite to the cast we started with, which actually turns out to be a very good thing.
The final step is to lower the opacity of the averaged layer and use the slider as a way of finding a happy median between the two opposite casts by letting one ‘shine through’ on the other. You’d probably think that this is achieved at the 50% mark but that’s not always the case, continue playing with it until you find a level you’re happy with. I’ve found 80% to be a good amount for this image.
Finally, I see this image as a little under saturated so I went ahead and added a Hue/Saturation adjustment layer and boosted the saturation to 60%.
And there we have it. More tips and tricks than you care to count, directions to a few helpful tutorials that will further improve your knowledge of reducing and adjusting colour casts, and an amazing technique that affords you complete control over any colour cast that dares to challenge you - using nothing more than the Average filter, Invert command and a few blending and opacity tricks.
I hope you found it helpful!
