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hand-blending high dynamic range (hdr) images using luminosity masks



Hand-Blending High Dynamic Range (HDR) Images Using Luminosity Masks

©2009 Tony Kuyper

Introduction

Several tutorial readers have written to ask about using luminosity masks to help blend different exposures in high dynamic range (HDR) scenes. It would seem logical to try this since luminosity masks allow easy access to specific tones and provide feathered blending of the tones they select. Unfortunately, it's not quite as easy as it sounds. Simply putting a layer mask of a luminosity selection onto one of the HDR exposure layers doesn't work too well. While a variety of luminosity masks can be made to mask different tonal ranges, it's hard to generate the perfect one to mask a specific exposure.

Luminosity painting (painting through a luminosity mask) could potentially be very useful in this situation. Luminosity painting allows the effect of the action-generated luminosity masks to be increased or decreased depending on how much paint is applied through the mask's selection. The technique essentially allows the creation of an unlimited number of user-created luminosity masks and thereby much finer control in the tones that are masked—or unmasked, as the case may be. So instead of relying on a computer-generated luminosity mask to mask the HDR exposures, luminosity painting should, at least in theory, be able to create a highly specialized mask tailored by the user for one particular exposure. Luminosity masks, as part of their creation, are perfectly feathered to blend with the image they are created from. This means that luminosity painting through these custom-made masks should be able to blend different HDR exposures fairly well.

I don't take many of HDR-type pictures, so my ability to test this idea is somewhat limited. I have one image from a few years back where I manually blended exposures, but it required so much Photoshopping afterwards that I haven't tried "hand-blending" since. While I used luminosity masks to facilitate this original blend, it was in a very crude manner compared to what luminosity painting can do. I thought it might be interesting to see how and if the blend could be improved using luminosity painting. The following sections describe the techniques I tried and what I learned in the process.

The steps outlined make use of the information in the Luminosity Masks, Luminosity Painting, and The Magic Mid-tones tutorials. I'll explain things the best I can, but some of the information here will assume familiarity with the techniques in those tutorials. Please refer to these tutorials for more detailed information.

NOTE: When this tutorial was written, different color settings were used to produce the luminosity masks. At that time, the Lights-series consisted of Expanded Lights, Lights, Light Lights, Bright Lights, and Super Lights. The Dark-series consisted of Expanded Darks, Darks, Dark Darks, Shadow Darks, and Super Darks. The luminosity masks have since been updated. The Expanded Lights and Expanded Darks have been removed and the Ultra Lights and Ultra Darks have been added, as discussed in the Luminosity Masks tutorial. The concept for blending exposures by painting through luminosity masks remains the same; just the mask names have changed.