Luminosity Masks

Landscape Photography:

• Increase dynamic range by through manual exposure blending. This is the same concept as HDR, but the results are often dramatically more beautiful and realistic. Please see below, where I dedicate a whole section of this article to this subject.
• Blend time to recreate the mood of a place. Capture various elements of a scene when the look best. For example, you can combine a sunset image with a "blue hour" shot taken 30 minutes later. This will show the beautiful sunset, and yet allow you to light up the building and show the streaking headlights of cars.
• Dodge and burn with much more precision and speed.
• Reduce high ISO noise to improve a Milky Way shot, without affecting the bright stars.
• Remove shadows.
• Targeted use of filters. Often times the effect you are using will look best when selectively applied to parts of the image, rather than to the entire image. Imagine adding the type of control you get with Nik, but then applying it to any 3rd party filter (Topaz, etc).

Black and White Fine-art Photography:

• Precise control over tone/contrast throughout the image. See this tutorial on How to Create Beautiful B&W Flowers.
• Dodging and burning with incredible precision. See the tutorial showing how the mountain image below was created by dodging and burning through luminosity selections.
• an Ansel Adams type of zone system that targets the image by tonality.
• Select objects and edges faster faster than the pen tool. 

Real Estate Photography:

• Exposure blending to retain exterior detail through windows. See this tutorial on exposure blending for real estate.
• Targeted color correction to deal with mixed lighting.

Composites:

• Luminosity masks not only offer options to enhance various components of the image, but also give you faster and more advanced objects to select/isolate subjects. For example, it's easy to select a subject from a seamless paper backdrop with standard selection tools; but if you need to isolate a subject from a complex background, luminosity masks can be a life-saver.
• Luminosity masks can also help create more convincing blends when there are variations in lighting, color, shadows, etc between different source images.

Portraits / Wedding / Sports:

• Manage less than ideal light by diminishing distractions or restoring details. Shooting people an mean chaos and a loss of control over lighting, luminosity masks can help you get back in control of the light.
• Recover beautiful sky color (with a single exposure of your subject and no need for flash)
• Control contrast by dodging and burning or using curves adjustments with luminosity masks.
• Easily lighten/whiten eyes and teeth.
• Use landscape techniques to create a beautiful sunset background behind your subject. 

That's a very long list, but by no means comprehensive. How do you use luminosity masks? Please leave a comment below!

When should you not use luminosity masks? This mostly comes down to a balance of quality vs speed. Luminosity masks probably aren't ideal for high volume work like budget portrait sessions or basic real-estate work. And you still need to shoot in great light for the best images (after all, luminosity masks are only created from the light you captured).

Other Luminosity Masking Options

As luminosity masking has grown in popularity, more software packages are adding basic levels of support. As a result, the general term "luminosity masking" has become a little confusing because it can mean vastly different things.  

While luminosity masking support can be very valuable in all sorts of applications (RAW conversion, HDR processing, etc), there is no substitute for creating luminosity masks in Photoshop. Luminosity mask support in other applications may serve some very useful purposes for offering a simple way to do simple tasks in those applications. But without Photoshop, you probably will not be able to do everything you need to process your image to its full potential. 

The following features make Photoshop a critical tool for working with luminosity masks:

• Luminosity selections. Luminosity selections are the MOST IMPORTANT tool in "luminosity masking", because they can be used to create MUCH more advanced luminosity masks that target specific areas of the image much more effectively than a general "L5" mask, for example. Probably 80% of the luminosity masks I create were painted via luminosity selections.
• The ability to work non-destructively on COMPLEX images. This means layer masks, adjustment layers, and smart objects.
• Custom luminosity masks. This means the ability to tweak the masks for precision based on luminosity, color, location in the image, etc. A few simple options or even a 10-zone system quickly become limiting if you cannot further customize them.
• The ability to blend multiple images. This can be used for exposure blending (increased dynamic range), perspective blending (enhanced compositions), focal length blending (to create wide angle images that do not have tiny background subjects), etc.
• And many more advanced capabilities only offered with Photoshop and 3rd party plugins.

If you have Photoshop, you can do all of the above (the various extension panels or actions you might use can certainly make things much easier, but everything is possible if you have Photoshop).

How to Use Luminosity Masks

Ok, enough about what the masks are, let's jump in and edit a photo. In this next video, I'll show you several ways you can use luminosity masks to improve an image. You'll learn how to use luminosity masks to burn (darken) some distracting highlights, to add some contrast to make key parts of the image pop, and to reduce saturation in a distracting light.

As you see in the video, there are many ways to use luminosity masking. In fact, you can use them anywhere you would use a mask or selection, so the applications are limitless. But you typically won't use the mask exactly as it was created (though I often use the default masks to control how sharpening and vignettes affect shadows). More often, you will want to apply the mask selectively. There are two ways to do that: by refining the mask, or by painting through a selection.

Refining Luminosity Masks

Refining a luminosity mask is a useful way to make sure that it only affects the desired areas of the image. It is also a good way to make parts of the layer more visible in areas that are only partially selected. There are three basic ways to refine a mask: paint on it (which is destructive), mask the mask (which is non-destructive, but only lets you restrict and not expand the mask), or use Photoshop's refine radius tool.

To paint on a mask, first click on the mask to make it active (or <alt/option>click it to see the mask). Once you have activated the mask, you can paint on it with any black or white brush. You may choose to do so freehand, or you might use a selection to help paint more carefully. Making the mask more white will increase visibility of the underlying pixels, and black will make them more transparent ("white reveals and black conceals"). You can also make gray pixels in the mask become more black or white by using the dodge and burn tools in Photoshop. This is a great way to make targete refinements of the mask.

To "mask a mask", you should put your layer with the luminosity mask into a group. Do this by selecting the layer and clicking on the group icon or pressing <ctrl/cmd>-G. You can then click to add a layer mask to the group. Any black added to the group mask will make any white in the underlying layer invisible. So in this way, you can remove areas of the mask. The beauty is that you can paint white on the group mask to restore visibility of the underlying mask. However, if the underlying mask is black, there is nothing you can do on the group layer to make that area visible. So you cannot expand the mask in a non-destructive way. 

The "refine radius" tool can be very useful to deal with edge issues when blending exposures, especially at high contrast edges. This tool can be found by clicking on your mask and then going to Select/Select and Mask (or Select/Refine Mask if you are using older versions of Photoshop). This amazing tool will automatically correct most "halos" around blended edges. See the following video to learn more:

Painting Through a Selection

Instead of creating masks for everything, you can also load a luminosity mask as a selection to control tools like the paintbrush. In fact, this is the most powerful way to create luminosity masks, because they can be extensively customized. 

There are many good uses for this approach, but the most common are for exposure blending or dodging and burning. For example, you could dodge and burn with layer masks, but you would need a new layer for each area you target - making the process cumbersome and your file much bigger than it needs be. Instead, you can simply <ctrl/cmd>-click on your luminosity mask load it as a selection, and then paint directly onto your gray dodge and burn layer.