White Balance Post Processing Overview, details to follow
Previous background posts –
Here, we’re looking at step #1 in this sequence of PP adjustments
- White Balance
- Highlight & Shadow Recovery
- Color Contrast
(click any image to enlarge)
And, in the beginning there was………
and it was covered with darkness – and light, sometimes too much light – and, like Goldilocks, occasionally just right.
How do we get this all “just right” – or close to it? The four adjustments listed above -usually done in the order shown – are basic to almost any image. Here we’ll look at White Balance (WB).
1. We start with getting the color correct (i.e., WB). Every adjustment that follows depends and builds on correct color. Think about it – if we start with incorrect color and then in subsequent step do things to adjust color (hue & tonal adjustments) we’re adjusting the wrong thing – and probably making it worse, not better.
What do we mean by “correct”? Correct in the sense that’s there is no color cast. No color cast means that white, black and all shades of gray in between are neutral (from here on, when I say gray, white & black are included). Neutral, in turn, means that the red, green and blue (RGB) components of any gray tone are equal
R=G=B = 0 is black
R=G=B = 255 is white
R=G=B = any value from 1 to 254 is a gray-tone somewhere between black & white.
If this condition is not met, then ALL other colors will have a color cast. It may not be perceptible but it’s there – and you don’t want it. In a later post we’ll discuss options for dealing with this in PP. However, the right time to get color correct is in your camera at the time you take the picture. I’ve already addressed color & your camera in agonizing detail in this three part series –
and they tell all that you need to know – and more. Read it unless you know it already.
One other point – shooting in RAW makes white balance correction a snap. Not shooting in RAW makes white balance correction a crap shoot at best – and your odds of success may not even be 1 in 12 under some lighting conditions. A word to the wise….
And away we go……
This is the Capture NX2 screen with our test image loaded. Nothing especially different or novel. Processing options and tools across the top, a large window on the right where our selected adjustments will appear, and a histogram.
Note – we’re working with a RAW image. If you choose to not shoot RAW – your bad, not mine; we’ll examine your self made problems in a later post.
We’re here to adjust WB. It’s actually pretty good since it was raining buckets and the camera’s WB setting was for Cloudy, but we’ll go through the steps anyway. In a later post we’ll look at some truly bad WB and how to deal with it. For the moment though, let’s just go through the steps as offered in NX2.
NOTE – All RAW converters provide the means to adjust WB. Be aware that this is the most problematic adjustment when using a 3rd party PP program and not the RAW converter provided by your camera’s maker. Some manufacturers (maybe all) don’t divulge the inner workings of their WB “secret sauce” and the result is that 3rd parties reverse engineering may not provide the same color correction for Nikon cameras as does the Nikon software (and ditto Canon, etc.)
Shooting in RAW means, among other advantages, that we can change any camera setting – ANY – after the fact and the resulting image will look identical to what we’d have gotten had we actually captured the image in-camera with that new setting. How cool is that? Now there are a few rare exceptions (ISO setting being the most notable and important – mess this up & there’s no turning back), but basically this says that RAW is the ultimate photographer stupidity safeguard. This is why NX2 has an entire adjustment window labeled Camera Settings (which is disabled if you load a non-RAW file, Nikon only). If we want to adjust WB, which is a camera setting, this is where we’d look. The next sequence of images illustrates just a few of the available WB controls. The number & type of options, plus their use, varies wildly from program to program. If you use another program, the “how” of what I’m discussing is up to you. If the options are fewer or the how is harder than shown here, and you shoot Nikon, you may be using the wrong program (or the wrong camera 😉 ).
This next sequence of images illustrate the main WB options available in NX2 (and others?)
Two main options exist. Set Color Temperature provides a set of standard lighting scenarios from which we can select – and fine tune. The range of scenarios is shown in the two images following this one. Secondly, we can use Set Gray Point to define neutral gray within our image by simply pointing at something true neutral gray (including B&W).
Below we see the 1st screen provided if we choose the Set Color Temperature option. It tells us that the camera’s WB setting when I captured the image was Cloudy (the 0,0 are fine tune options within Cloudy). This was the correct setting for the situation BUT it also is my standard WB setting. I do not use Auto for reasons I’ll explain when we get to the real details.
From here there are two main options – choose something other than Daylight (Cloudy is one of three daylight options) or fine tune cloudy. Further, one can change the color temperature directly (in some programs this is the main or only WB option) and/or change the color Tint.
Below we see the lighting scenarios, such as the current Daylight selection, that are available in the New WB drop down menu.
The absolute most accurate WB can be obtained by actually setting the gray point. This assumes that there is a true gray point somewhere in your image(or that you’ve saved such a setting from another image made at the same time where you inserted something into the picture space such as a gray card for just this purpose. This is a common approach – add a gray card to the image when making your first shot and save this WB setting for use with following images. Read this if you’re not familiar with this concept.
Choosing the Set Gray Point option provides us three choices – Point, draw a rectangle, or actually specify the Red & Blue component adjustments (better left for fine tuning one of the first two options if they give a color that’s either too warm or cool for your taste).
If you look near the lower left corner of the next image, you’ll see where I placed the eyedropper pointer to define what I wanted to be neutral. As you’ll see in the image following this one, a small WB correction was made even though I had the correct camera setting at capture. This can occur for several reasons –
- The sample point, in reality, wasn’t a true neutral point or
- It was true neutral and the day was not an exact duplicate of whatever the program designers specified for Cloudy in their canned presets. This is most often the case, but in the current image I wouldn’t swear to it as that water I sampled had lots of stuff going on in it. But, anyway…….
This next image shows the results of the previous Set Gray Point adjustment. The image color has changed on the left and the WB adjustment tool window shows the change – the image has been “cooled” slightly by increasing the Blue component relative to the Red.
You may (or should) have wondered, since neutral is R=G=B, why are we only adjusting R&B. There’s no need to change all three. The fact that both R&B in this case were increased tells us that they were both low – in comparison to the G component with B being even lower than R – and this is the adjustment needed to make R=G=B.
And here’s what we have in comparison to our starting image after the first of our four basic post processing steps, White Balance. Original is on top and post-WB is below.
Truth be known, I believe the original is closer to what I saw but I’m going with this in order to make changes more readily visible even if not exactly true to real life.
NOTE: In case you think, based on this long, tortuous explanation that adjusting WB is an equally long, tortuous trial in front of your computer – it took 5 seconds to do everything needed to get from the starting image to the completed WB correction. Oh, that I could write that succinctly.