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Asymmetrical luminosity masks for more accurate editing in Photoshop

Using and creating 16 bits asymmetrical luminosity masks in Photoshop for ultimate control

An article and tutorial on the use and creation of asymmetrical luminosity masks for better and more accurate tonal separation and editing in Photoshop

In my recently released version V1.3 of the B&W Artisan Pro panel for B&W editing I’ve created, there is a novelty I would like to give you some more insight in as it is an essential part of editing photographs with a higher degree of luminance separation and hence control. Even though the panel automates every single step in my workflow, I believe in sharing information that will be of added value for every serious photographer in the digital age.

The novelty that I built into the panel is a variation and combination on the luminosity masks and zone masks Tony Kuyper, the inventor of the luminosity masks, is suggesting on his website and are called asymmetrical masks. Basically zone masks are asymmetrical masks, but I found a way to make the asymmetrical zone masks more accurate and at the same time with the full depth of 16 bits, when compared to the usual zone masks. I will try to explain in this article what asymmetrical masks exactly are and how to create them yourself with 16 bits depth.

Let me start with the discussion on 16 bits luminosity masks versus the more ubiquitous 8 bits luminosity masks. 

The practical effect and benefits of using 16 bits luminosity masks instead of 8 bits luminosity masks are negligible and only visible when pushing the contrasts/adjustments to extremes. One reason for this is that channel masks that can be created in 16 bits, in this case luminosity masks, are only practically useful when they’re loaded as selections. Selections in Photoshop are always 8 bits. So this mitigates the effect of the full channel depth of 16 bits.

An important feature in the B&W Artisan Pro panels have always been the use of micro zones to adjust tonal values using free form selections within a specific tonal range. Up to now I’ve always used standard, linear, luminosity masks, including symmetrical mid tone masks, automatically generated when hitting a preset in the panel, to enable a feature like micro zones. Since linear luminosity masks (why they’re called linear will be explained in this article as well) work only well to isolate a specific tonal range or zone when they’re at the opposite ends of the grayscale, zone 0 or zone 10, and do not isolate a targeted zone exclusively when trying to isolate zone 8 for example, the solution would be in a non-linear symmetrical or asymmetrical mask.

Conventional luminosity masks like Lights2 or Darks3 are linear masks. A luminosity mask created for mid-tones is symmetrical as it is intended to exclude the highlights and shadows. A variation on luminosity masks are the zone-masks that also have been developed by Tony Kuyper and are asymmetrical as they target only a specific zone, while excluding other zones. 

See the following pages for examples of the asymmetrical masks used in this panel and how they differ from conventional, linear, luminosity masks.

A practical example when applied to a real photo

Creating a customized asymmetrical mask

The following method I’m describing targets just one zone, zone 3 from the example, and it’s a method that will ensure a 16 bits channel mask. It’s an alternative method based on calculations and adjusting straight on the channel mask with levels adjustments to avoid loading the mask via selections. Once a selection is loaded and is saved, it basically becomes an 8 bits mask since a selection is always 8 bits in Photoshop. Other zones, or even extended, less restricted versions of that zone, can be derived and developed from the method demonstrated here for this specific mask using lighter luminosity masks like Lights2.5 instead of Lights3.5 I’m using for this mask. It takes a bit of trial and error and also quite some work as you always need a grayscale grid as used in my method to accurately isolate the zones when building the mask. You can download the grayscale grid here.