Lightzone ZoneMapper: a primer for curves users

As I mentioned before, I intend to write some posts on editing techniques in Lightzone. Not really tutorial, more handy hints and things I've picked up along the way. I hope it will be useful to users of other editing tools who may be considering Lightzone.

As a start I thought I'd start with the central tool in Lightzone, the ZoneMapper. I came the the realization that without an introductory post like this, any other post would be excessively long. This is a mixture of an introduction of those new to Lightzone but more specifically a comparison with curves from other tools (I've used Picture Window Pro) about achieving the main results.

getting to grips with the ZoneMapper is IMO essential to getting the most out of Lightzone. It'll also be at the heart of many of my other posts in this series, and I'll refer back to this one when I do.

So to start with basics.

Introduction

I won't go on about the zone system, tonal values and all that. Quite frankly I find it confusing and unhelpful. I'm going to stick to a practical description based on visual perception: it's the way Lightzone is designed to work and should be understandable to all.

The ZoneMapper is a tool designed to make visual adjustments to the tonal balance of an image. To my mind its power lies in two features: the simple, can't-go-too-far-wrong interface and the tie-in to the ZoneFinder view that allows easy identification of tonal ranges.

It needs to be noted that the divisions are exponential. The documentation says that each division represents 1/2 stop of exposure, in practice I find it easier to think of each division as 1-bit in a 16-bit system. Each is roughly equivalent.

Another thing to note is position locking. When a zone boundary is selected it is locked in place until moved. This makes it possible to isolate the range to be adjusted in a way that is difficult with curves. In Lightzone 3.2, this can be combined with the colour/tone range selector for very fine control of the range of application without the need for masking.


Anatomy of the tool

First to show what the elements are. At the top of Lightzone's tool stack is the sample window. It can show the ZoneFinder, a Colour Mask (more of which below), a histogram or a cursor sampler. Each of the first 3 gives data on what is currently visible in the edit window. The yellow highlight in the ZoneFinder pops up when the cursor is hovered over a zone boundary. This shows the areas in the Zone immediately above the boundary.
It is important to note at this point how the ZoneMapper works at a pixel level. While the ZoneFinder shows whole areas in a given zone, this is a broad average, the ZoneMapper actually affects all pixels at a given pixel value. The extreme would be a series of dark and light stripes. While the ZoneFinder might show a mid-range zone, the actual pixels are a high end and a low end. The ZoneMapper will treat them at the pixel level as high value and low value, not their zone average.

Below the main zone selector are 2 tabs, one for the normal blending options, the other for colour masking (see below).

Brightening: Upward movements

This is quite straightforward. Take a zone marker and move it upwards. This is directly equivalent to generating a 3-point curve above the central line.

Moving a zone all the way to the top is the same a curve locked to the top edge or input values in a levels tool.

The white point

White point can be moved by moving the top zone marker. This is equivalent to locking a curve to the right edge or the output value in levels.

Darkening: Downward movements

The opposite of brightening: take a zone marker and move it down. Equivalent to curves below the central line.

Taking a zone marker all the way to the bottom is equivalent to locking a curve to the bottom edge or lower input value in levels.

The black point

As with white point, the black point can be adjusted by moving the bottom zone marker up: left edge in curves or lower output value in levels.


Contrast adjustments

This is where the real power of tonal tools shows through. By taking two zone boundaries and moving them apart (lower one down, upper one up) contrast is enhanced for the range in between.
Moving them together reduces contrast.

The big difference is that in ZoneMapper it is not possible to do whacky things like this:

because the zone markers can never be overlapped.

Locking zones

One thing that s particularly good about the ZoneMapper is the ability to lock a zone boundary and only make adjustments on one side or the other (or both, independent of one another). Doing similar in curves takes a lot of adjustment points.

Colour masking (for version 3.x)

In the current versions of Lightzone there also exists the ability to mask each tool by colour/luminosity range. This is useful if e.g. you only want to do mid-tone adjustments with control on the definition of mid-tone. The 4 little arrows at the bottom show this in action. From the left the arrows are: dark feather limit, dark feather start, light feather start, light feather limit. Here I've shown the Colour Mask window which shows the mask in effect for the current tool. The 3 little RGB dots show there is a colour mask in effect for that tool (normally they're orange).
A quick note on RGB versus Luminosity

There are 2 ways to employ the ZoneMapper - luminosity only or on RGB. The first is the normal way to use it, keeping RGB relations in tack. The RGB performs the adjustments on each channel separately. I can't remember ever needing RGB setting.

So there it is, I hope that proves useful.