We all put on masks (not Covid ones, thankfully) all the time. Our masks make us look better to other people. But I’m not talking about our social interactions. We are image makers, so we also use masks in our editing tools to make our images look better. Both Photoshop and Lightroom have masks, but they are very different. Understanding the differences helps us better understand our craft.
What are they
In their simplest form, masks limit the extend of the edits we make to an image. All of our editing software let us make global adjustments to an image, like increasing or decreasing the overall exposure. Most of our editors also allow us to restrict edits to selected parts of the image.
You know the situation. After we get the overall look of an image balanced the way we like we often have to “drill in” and work on smaller parts. For instance, maybe a part needs to be brightened to make it stand out the way we want or darkened to call less attention to itself. No matter what your software calls it, masks are used for this.
But how we do it and how they work on the image can vary greatly.
©Ed Schlotzhauer
A mask
In the general sense, a mask allows us to isolate part of an image so that we can make selective edits.
Without masks all of our edits would be global. That is, what we do would affect the entire image. To selectively modify only parts of the image, though, we need the ability to restrict the area to be edited. In a sense, a mask is kind of like a stencil that keeps us from painting outside of an area.
For photography, the concept of masks comes from the darkroom. In the traditional darkroom, printers used bits of paper or sheets with shapes cut out to hold light back from selected areas or to add light to selected areas during exposure of a print. This was called dodging and burning. It required a lot of planning, and it was a very tedious and labor-intensive process. One mistake and hours of work could be ruined. I personally am very glad we do not do that now.
Lightroom vs Photoshop
I’m going to use Lightroom Classic and Photoshop as my examples. They are what I know, and I think they are the most commonly used editors of their specific kind. Yes, kind, because for all their similarities they are 2 different kinds of thing. These differences are important to us, and we need to have some understanding of how they work in order to use them wisely.
The most fundamental difference is that Lightroom never modifies pixels while Photoshop will gladly do anything you want to your pixels. Because of this basic difference, the way they deal with masking and editing is also completely different.
In a sense, Adobe has created a problem for their users. They sell the 2 premier image editors. And the products are tightly linked, and users often have to use both of them, but they are so different that it causes confusion.
©Ed Schlotzhauer
Photoshop
Photoshop was the first capable and widely used image editor. It springs from the days when images were only pixels. It is a pixel editor, even with adjustment layers and blending modes.
Photoshop is a bare knife. It eagerly does whatever you tell it to do to your image. Like a sharp knife in skilled hands can do great work, the same knife in unskilled hands can be dangerous. It will be glad to shred your pixels.
Inside Photoshop, a mask is a black & white image that is attached to a layer. Whatever adjustment you do on the layer is restricted by the mask. The mantra is “white reveals and black conceals”. That is, where the mask is white the adjustments are made on the underlying image. Where the mask is black, the adjustment is ignored.
But note that the mask is just another bitmap image. It can contain any set of pixels including shades of grey. For instance, sometimes frequency separation editing is done by doing something like taking, say, a copy of the green channel and pasting that into an adjustment layer as a mask. That is a complex mask.
Also, we modify images by building up layers of changes. The order of the layers is very important in Photoshop. The changes are always applied in the order you specify in the layer stack.
So in Photoshop you can do anything you want to the pixels. They can be stretched and blurred and painted over and, well, there is little limit. Masks are just another kind of bitmap that lets us limit the area modified by a layer.
©Ed Schlotzhauer
Lightroom
Lightroom Classic (I will leave the “Classic” off in the future, because it is the only one I use) is the newer product and it brings a completely different design and technology approach. It is specialized to be the editor of RAW images like Photoshop is specialized to be the pixel editor.
Lightroom has become my first and often only step in editing images. One reason I go to Photoshop less is because Lightroom has added very capable masking ability and they continue to enhance it.
But masks in Lightroom are a totally different thing from Photoshop. Since Lightroom is designed to be incapable of destroying pixels, they have adopted a technology of keeping “instructions” about the edits to be done rather than actually doing the edits. Same for masks and their edits. These are separate from the image. They are then applied to the original RAW file whenever it needs to be viewed. And it does not really matter what order you do edits.
Generally, Lightroom masks are constructed by combinations of gradients and range selections and brush strokes. The shapes can be composed together to make complex and useful masks. Some “AI” aids are available as shortcuts for selecting the sky, or people, for instance.
©Ed Schlotzhauer
Lightroom markup example
The edit instructions are just text that is kept separate from the image and is processed by Lightroom as needed. Here is a sample of the instructions for one of my images (this is only part of the text file, it defines one mask):
<crs:MaskGroupBasedCorrections>
<rdf:Seq>
<rdf:li>
<rdf:Description
crs:What=”Correction”
crs:CorrectionAmount=”1″
crs:CorrectionActive=”true”
crs:CorrectionName=”Mask 1″
crs:CorrectionSyncID=”4F05D072D78C40239D264FC0F8F45469″
crs:LocalExposure=”0″
crs:LocalHue=”0″
crs:LocalSaturation=”0″
crs:LocalContrast=”0″
crs:LocalClarity=”0″
crs:LocalSharpness=”0.215228″
crs:LocalBrightness=”0″
crs:LocalToningHue=”0″
crs:LocalToningSaturation=”0″
crs:LocalExposure2012=”0.27395″
crs:LocalContrast2012=”-0.100282″
crs:LocalHighlights2012=”0″
crs:LocalShadows2012=”-0.188717″
crs:LocalWhites2012=”0.127177″
crs:LocalBlacks2012=”-0.061475″
crs:LocalClarity2012=”0.730341″
crs:LocalDehaze=”0.631532″
crs:LocalLuminanceNoise=”0″
crs:LocalMoire=”0″
crs:LocalDefringe=”0″
crs:LocalTemperature=”0.274462″
crs:LocalTint=”-0.102011″
crs:LocalTexture=”0.169762″
crs:LocalGrain=”-0.100026″
crs:LocalCurveRefineSaturation=”100″>
<crs:CorrectionMasks>
<rdf:Seq>
<rdf:li
crs:What=”Mask/CircularGradient”
crs:MaskActive=”true”
crs:MaskName=”Radial Gradient 1″
crs:MaskBlendMode=”0″
crs:MaskInverted=”false”
crs:MaskSyncID=”780243712C904039AF01C58DADCB61FA”
crs:MaskValue=”1″
crs:Top=”0.219066″
crs:Left=”0.694605″
crs:Bottom=”0.301111″
crs:Right=”0.787517″
crs:Angle=”0″
crs:Midpoint=”50″
crs:Roundness=”0″
crs:Feather=”34″
crs:Flipped=”true”
crs:Version=”2″/>
</rdf:Seq>
</crs:CorrectionMasks>
</rdf:Description>
</rdf:li>
</rdf:Seq>
</crs:MaskGroupBasedCorrections>
It looks intimidating, but it is not made for us to read. Computer Science people call this a markup language. Computers process it efficiently.
It’s our technology
Photoshop deals only with pixels, and it can change the actual pixels of your image in any way you would like. There is no limit, and it can make changes that are unrecoverable. Lightroom edits are more limited in scope and only deal with information about the adjustments you would like made to your image. A benefit of Lightroom is that it refuses to destroy any pixels.
This applies to masking, too. Masks in Photoshop are bitmap images that can be as complex as the image itself. The mask is another layer to paint or edit like other images in Photoshop.
©Ed Schlotzhauer
Masks in Lightroom are more limited, but still completely useful. The masks are combinations of the shapes Lightroom knows about and lists of changes to make within the shape. It does not matter what order you do adjustments in Lightroom.
We need to be aware of these basic design features as we are using the products. Photoshop works directly on pixels. Lightroom keeps information about how to change the look of pixels. They are fundamentally different in design. When we do not keep these behaviors in mind, we can become frustrated when switching between the tools.
It is part of the technology we use to create our art. The better we understand how it works the more skilled we can be at using the tools.