Highlight Shadow Recovery Post Processing Overview, details to follow
Previous tutorial overview posts –
- PP Tutorial Software Background
- PP Tutorial, Part 1
- Part 2, A quick end-to-end overview
- PP Tutorial, 2 – Quick Overview, White Balance
Here, we’re looking at step #2 in this sequence of PP adjustments
- White Balance
- Highlight & Shadow Recovery
- Color Contrast
(click any image to enlarge)
And, in the beginning there was………
Our image as captured in-camera (RAW),
followed by the next image which shows the effect of a PP white balance (WB) adjustment.
We started with WB first since getting accurate color is critical to all adjustments that may follow. Once we’ve got the color right, we work our way through the other fundamental adjustments – normally starting with those that have the greatest impact and working our way down the list to those that are more fine tuning and/or local in nature.
The next “biggy” is to get the exposure right. The extent to which this is needed depends on the lighting conditions at the time of capture. In the best case, when the light’s tonal range is such that your entire histogram fits easily within the left and right borders, little or nothing is needed in this step. Worst case, you at least had to use excellent technique and equipment such as graduated neutral density filters to control the extreme tonal range (greater than fits the histogram) and/or multiple exposure techniques such as HDR or Exposure Fusion – else you’ve got a mess on your hands.
For help with histograms and exposure see
In this image, we’re in the best case world although there are a few image areas that are brighter or darker than I’d like. We’ll look at how this can be handled and, in later posts, look at more extreme cases.
Before going further below is the histogram for the original image, as captured, followed by what it looks like after the WB adjustment. We see that the original histogram has no shadow/highlight problems to speak of (partly because of the ambient light and partly because this is a thing that I pay great attention to when capturing an image. I look at the preview LCD often – but never to look at the image, I’ve already seen that in the viewfinder. I use a histogram option that shows all three color channels plus the combined histogram together with an option to switch among them and have blown areas flash. If there’s a problem I correct it immediately (PP is too late) by either
- EV compensation and/or
- Graduated filters
- Bracketed exposures for HDR or Exposure Fusion in PP
- or some combination of all of these, but regardless I don’t stop while there’s still an exposure problem – inexcusable.
You can see that the WB adjustment, alone, had little impact on the histogram – nor should we have expected it to. In the WB post, I noted that the WB correction had the effect of cooling the image a little by increasing the blue component. You can see that illustrated in the blue channel change from the top to the bottom histogram.
If there is a problem with the exposure of this image, it’s that the tones are shifted too far to the left – that is, the overall image is a little too dark. Now, even though it actually was on the dark side – a tropical storm dumped 6+ inches of rain on us that day – I didn’t see things as dark as the image shows. That may just be me, but I get to choose. Although there are a gazillion ways to address this problem, I’ll only consider two here. In a later post, I’ll come back and beat the details to death.
Since we’re dealing with a RAW image, I’m going to compare two options that only apply to RAW and save the rest for another post.
- Exposure Compensation Adjustment (nearly every RAW PP program offers you this)
- Active D-Lighting (NX2 & Nikon cameras only, plus you must have this enabled in-camera at capture or it’s not available in NX2. This is not to be confused with NX2’s D-Lighting, no “Active”, which can be used on all types of images from all types of cameras)
#1 – Exposure Compensation (EV). This, like all RAW camera adjustments, makes the image appear identically to what you’d have gotten had you dialed up the same EV at capture (well, almost but that’s another story). If you saw this histogram at capture and wanted to make the overall image brighter what would you do? You’d dial in positive EV to shift the histogram to the right (brighter) since there’s room before we blow out highlights by running into the right edge. How much? – experiment, practice & learn.
Let’s try 2/3 of a stop (my camera’s EV is adjustable in 1/3 increments, but in PP we can make it whatever we want). Shown here in NX2’s Exposure Compensation window we see the effect of that adjustment. The histogram fills the the entire range from black to white – perfect. The fact that it’s still biased towards dark is more a statement about the tonality of the subject matter than about whether the image is underexposed or not.
and below is the color channel histogram version we used previously but now showing the 2/3 EV effect.
You’ll see in comparing it to the copy of the post-WB histogram from above that we got the right-shift that we wanted.
How about the post-WB vs. +2/3 EV image comparison. At the top is the post-WB, pre 2/3 EV image and below it is the image with WB + EV adjustments. As expected the lower image, with the +2/3 EV, is brighter overall than its predecessor.
#2 – Active D-Lighting. This 2nd RAW file exposure adjustment option is the exclusive Nikon-RAW only option. I always have this enabled in my camera at its “Normal” setting. If I don’t like the result I can turn it off in PP (not quite the same as off in-camera but close enough) but rarely do. A big reason to have it on in-camera is that if it’s not on then this option is not available to you in PP.
Here is the Active D-Lighting menu from within NX2’s Camera Setting window. The asterisk indicates the value selected in-camera when the image was captured. Let’s see what Extra High does for us since higher general equates to brighter.
The 1st image below is the Active D-Lighting result at Extra High. Below it, for comparison is the +2/3 EV adjustment result we did previously.
There’s not a lot of difference – which is a good thing if both options are aimed at the same thing – but the Active D-Lighting image does appear to be a little brighter. When comparing the two histograms (D-Lighting top and 2/3 EV below) we that the Active D-Lighting did a more thorough job of raising the brightness level at all tonalities. The 2/3 EV did what it should have done, by comparison, and mostly just shifted the entire original histogram to the right. Which is “right”? Which is “better”? The answer is – which do you prefer?
Note that the D-Lighting adjustment did blow out some highlights in the red channel (which is climbing the right wall). This is probably in the red leaves on the rock in the foreground and is easily fixed in a later step.
I want to go with the Active D-Lighting result. Toning things down later is easier than brightening. Here’s our results thus far with –
- Original image at the top
- WB correction effect 2nd
- WB + Shadow/Highlight recovery third
In the next post, we’ll build on the above two adjustments and take a look at adjusting Color Contrast which helps with flatness in an image.