home
contents
copyright
donations
contact

10.6 Selection

Of all the processing features available in Photoshop, the most powerful—for processing bird photos—is, by far, its array of tools for selecting parts of an image and processing those elements differently from the rest of the scene.  The flexible and efficient selection methods in Photoshop are nothing less than a godsend to bird photographers.  The reason is simple: people who spend time looking at (or even buying) bird photos do so because they are, in the majority of cases, inordinately fond of birds.  They therefore place greater importance on the aesthetic qualities of the bird in any given image than would a casual viewer, and are by-and-large impressed the most by photos in which the bird stands out prominently from its background.  Notwithstanding the proverbial exception-to-every-rule, for avian art the bird, as the principal subject, needs to occupy a central place in the awareness of the viewer (even if not centrally located in the image frame).  Differential processing of the bird versus its background—even if only subtle—is thus a key capability in any workflow involving the producion of avian art.
    We’ve already seen, in section 10.3, that Photoshop allows for efficient differential processing via the separation of image elements into different layers (though we’ll see later that differential processing is possible even without the explicit use of layers).  In order to separate image elements into different layers, however, you first need to be able to select them.  That is precisely what we want to address in this section: how to select the bird (or any other part of the image) via the cursor-controlled tools available in Photoshop.  In particularly, we’ll want to explore how to select the bird efficiently (without having to spend excessive amounts of time fiddling with the computer’s mouse) and accurately (so that the selection boundary follows the bird’s outline with sufficient exactitude).
    We will proceed via concrete examples.  The first is illustrated below.  Here, the bird has been hastily selected via the Lasso tool in Photoshop.  The black-and-white dashed line roughly following the bird’s contour indicates the current selection.  As you can see, this selection isn’t perfect, since some parts of the bird lie outside the selection, and a few pixels from the background fall within the selection.  For some applications, such a sloppy selection may be good enough for the task at hand, but for many it won’t.  We’ll see shortly how to get more accurate selections using other tools.


Fig. 10.6.1: Selecting the bird using the Lasso tool.  This selection is very
sloppy: some of the bird lies outside the selection, and a few pixels from
the background lie within the selection.  The Lasso tool is very difficult
to use (especially with a trackball), so I recommend avoiding it.

The way this selection was created is as follows.  First, I clicked on the Lasso tool’s icon in the toolbar.  Then I clicked on an arbitrary starting point on the bird’s outer boundary, and then without releasing the mouse button I dragged the mouse cursor (using my computer’s trackball, which is similar to a mouse) so as to trace the outline of the bird.  When I had traced a complete circuit around the bird’s outline, I released the mouse button.  Selecting a bird this way can be quite tedious, and is rarely as accurate as you’d like. 
    Fortunately, there are better options in Photoshop for selecting complex shapes—options that can be far more accurate without requiring much more effort (once you’ve had some practice).  Some of Photoshop’s selection tools are depicted in iconic form in the figure below.


Fig. 10.6.2: Some of the selection tools in Photoshop’s
toolbar.  Clicking on a tool’s icon in the toolbar turns
your mouse cursor into that tool.  For the icons with a
small triangle in the lower right corner, holding down
the mouse button while clicking the icon will bring up
a second palette with additional tools in the same family.
Most tools have keyboard shortcuts, for faster access.

We’ve already encountered the Lasso tool; the Magnetic Lasso tool is similar, except that the computer tries to help you by fixing what it perceives as your “mistakes” (i.e., errors in the trajectory of your mouse cursor), while you’re in the process of making them.  For example, if while tracing the bird’s contour with the mouse cursor you accidentally slip and veer outside the bird’s contour a bit, the Magnetic Lasso will (in the ideal case) notice your mistake and automatically correct it for you by re-routing the selection boundary to correspond more closely with the outer edge of the bird.  This can work well if the bird’s contour is strongly defined in the image (i.e., via an abrupt contrast differential at the pixel level), but in many cases the tool will get confused and re-route your selection in a way that makes it worse than if it hadn’t intervened.  This tool can be very frustrating to use.
    Fortunately, there’s a better way: the Quick Selection tool.  This is the method I use for 95% of my work.  It has some predictive intelligence built into it, much like the Magnetic Lasso, but is far easier to control, as we’ll see.  The main technological difference is that with the Quick Selection tool you’re selecting regions, not boundaries, and the tool can quickly infer what you’re trying to select in the image by studying the pixels you’ve already selected (as well as those you’ve explicitly de-selected).  Because it has more data to work with (i.e., more pixels to learn from), it often makes much more intelligent decisions than the Magnetic Lasso.  Let’s consider how this remarkable tool can be used in practice to rapidly and accurately select a bird from an image.
    After clicking on the Quick Selection tool’s icon in the tools palette, you’ll then need to select a brush size, as depicted in the figure below.  The “Diameter” slider controls your brush size (we’ll consider “Hardness” in just a moment—for now you should leave it at 100%—but the other parameters you can simply ignore).  A good rule of thumb is to start out with a brush size that is larger than the bird’s eyeball, but smaller than its head.


Fig. 10.6.3: Setting the brush size in the Quick Selection tool.
The brush size is important, because you’ll be using the brush
to sweep out regions that you want to select, and if the brush
is too big it won't be able to fit in all parts of the bird, while
if it’s too small it’ll take to longer to sweep out the whole bird.
A good rule of thumb is to choose a size larger than the bird’s
eyeball but smaller than its head.  You’ll see the size of your
cursor change as your move the Diameter slider.

Once you’ve chosen a brush size, you’re ready to select the bird.  To do so, simply click the computer’s mouse anywhere inside the bird, and while still holding down the mouse button, drag the mouse cursor around inside the subject.  Photoshop will try to intelligently expand your selection to the nearest natural boundaries in the image.  In many situations, this works very well—often extremely well—in which case you’ll see the selection contour almost magically expand to the precise outline of the bird.  In other cases it’s not quite so impressive, but at least in the case of birds I’ve almost always found this tool to be the most efficient means of selecting the subject.  It does require some practice, however, and there are a few important tips you need to be aware of.
    First, you can use the tool to both add to the selection and to subtract from it.  Note that in the tool’s settings pane there are several icons, two of which look like this:


Make sure you click on the left icon (with the “+” sign) before you begin using the tool.  That will allow you to add to your original selection by making additional clicks and sweeps with the mouse.  If you accidentally draw outside the bird, or if Photoshop is too aggressive in automatically expanding your selection region, you can de-select regions by holding down the option/alt key while using the tool.  Holding down the option/alt key temporarily puts the tool into its “subtract” mode; you’d get the same behavior by exlicitly clicking on the second icon shown above (the one with the minus sign), but I find that it’s much faster to just keep my finger on the option/alt key when I’m using this tool, and then I can quickly press or release that key as needed to switch between the add and subtract modes.  Once you become skilled at using this tool in both its add and subtract modes, you’ll be able to rapidly select just about any bird through a series of sweeps with the Quick Selection tool.
    Note that you can use the tool in subtract mode even on regions that haven’t been selected—doing so explicitly tells Photoshop that you don’t want it to select that region later when you go into the add mode and sweep the cursor nearby.  This can be useful when you notice that some part of the bird blends into the background.  If you just used the add mode you might find that when you near that part of the bird the selection suddenly expands to include the entire background region, which might then take a bit of work to explicitly de-select.  If you were instead to sweep out the “off-limits” area in the region where the bird blends with its background, effectively tracing out a boundary that the selection should not cross, then when you later switch to the add mode you should find that Photoshop is more reluctant to expand the selection into that off-limits region.
    When using this tool you’ll also need to make changes to your brush size periodically.  As suggsted above, a good rule of thumb is to start with a brush size that’s small enough to fit within the bird’s head.  If you start with a brush that’s too small you’ll find that Photoshop doesn’t expand to the bird’s contour as well, and may instead just expand to the nearest feather or group of feathers, requiring more work on your part.  The behavior of the expansion algorithm used by Photoshop is affected by the brush size, with a larger brush indicating to Photoshop that the contour it’s looking for is on a correspondingly larger scale.  Once you’ve got the outline of the bird roughly selected, it’s time to switch to a finer-scale brush and to zoom in a bit (so that only part of the bird will probably fit on your screen).  Now you can refine the selection boundary to more closely match the contour of the bird.  When doing this I make frequent use of the option/alt key to rapidly switch between the add and subtract modes of the tool, to nudge the selection boundary back and forth until it precisely follows the bird’s silhouette.  When working at the finest scales it’s sometimes useful to resort to single clicks of the mouse button, rather than sweeping with a drag-and-drop type of motion, or at least to use smaller sweeps rather than continuously “painting” as before.  Rest assured that you’ll get better at it as you gain more experience using this tool.  Just keeping working at it.  It’s well worth the effort you put in now to become more efficent for later.


Fig. 10.6.4: Selecting the bird with the Quick Selection tool.  This selection was made
in about five seconds by sweeping a medium-sized selection brush within the interior of
the bird.  Some additional work remains, however, since a few parts of the bird remain
unselected, and a few pixels outside the bird (the berry behind it) have been selected.
These finer-scale adjustments can now be made using a finer-scale selection brush.
You’ll want to zoom in (using cmd+ or ctrl+) to make those fine-scale adjustments.

    Once you’ve got the bird selected, it’s a good idea to either save that selection or to copy the bird to a separate layer (or both).  Choosing menu option Select and then Save Selection allows you to store this selection under a specified name, so that you can call it up again later, if needed (via Select > Load Selection).  Alternatively, you can press cmd-J on a Mac (ctrl-J in Windows) to automatically create a new layer containing only the contents of the selection.  Each of these two options has its own advantages.  Saving a selection is slightly more flexible than creating a new layer, because when you call up the selection later you’re free to modify the selection boundaries if needed.  Also, when saving into a Photoshop file (*.psd), a saved selection will take up less space than an additional layer.  Layers, on the other hand, have some advantages of their own.  Once you’ve created a separate layer containing the bird, you can apply other processing filters (e.g., altering the saturation, sharpness, or contrast) to just that layer; a single click of the mouse then allows you to turn that layer on or off, thereby allowing you to rapidly assess the overall effect of the modifications you’ve made to that layer (relative to the original pixels in the underlying base layer). 
    For especially difficult subjects I sometimes resort to the Quick Mask mode, which is activated by clicking this icon in the tools palette:


Note that Quick Mask is a mode, not a tool.  Once you’ve activated this mode, you need to select the Brush Tool, which will now be set to paint in red (which is why in previous tutorials I’ve referred to it as the Mask of the Red Death*).  Anything that you paint red in Quick Mask mode will be enclosed in a selection when you transition out of Quick Mask mode (or, depending on how you have the tool set up, it may be the parts not painted red that end up being selected—but in that case you can then invert the selection via Select > Inverse).  The figure below shows a sloppy attempt to paint a bird red in the Quick Mask mode (note that the berries are naturally red, and haven’t been selected).
Fig. 10.6.5: Selecting the bird using the “Mask of the Red Death” (Quick Mask).
Simply paint the bird with the Brush Tool.  If you make a mistake, switch colors
and unpaint the mistake.  When you leave the Quick Mask mode, everything
you’ve painted red will be selected.  The actual color used to depict the mask, as
well as the behavior of the mask—i.e., whether it is the painted regions or the
unpainted regions that are selected—can be specified in the Quick Mask
Options window (double-click the Quick Mask icon to show this window).

If you accidentally paint outside of the bird, you can very quickly fix your mistake by pressing the “X” key (which swaps the foreground and background painting colors for the current brush) and then un-painting the area you mistakenly painted; alternatively, you can use the Undo feature in Photoshop by pressing ctrl-Z or ctrl-shift-Z.
    When the Quick Mask icon is clicked a second time, the regions that have been painted with the Quick Mask brush will then be enclosed in a selection boundary, just as if they had been selected with one of the standard selection tools.  The advantage of the Quick Mask tool is that it allows you to (more easily) specify what I call fuzzy boundaries.  Imagine an image in which part of the bird fades into the background.  The exact boundary between the bird and the background in that region may be entirely imperceptible.  If you were to arbitrarily impose a selection boundary where you imagine the contour of the bird to lie in this region, and then apply some digital processing which makes the bird stand out more from its background (e.g., making it darker, or more saturated), the effect in the region of ambiguity between the bird and its background will often be to produce an unnatural-looking contour that many viewers will quickly perceive as an artifact of digital manipulation.  In other words, it won’t look good.
    In these cases it’s possible to instead use a soft-edged (rather than hard-edged) brush in the Quick Mask when painting the bird red, so that you can effect a smooth selection gradient in the region of ambiguity between the bird and its background.  When you switch out of Quick Mask mode you’ll see a selection contour that looks just like any other, but Photoshop will remember that the selection in the ambiguity region follows a gradient, and will respect that gradient when applying digital effects to the selection, and/or when blending a layer created from the selection with layers beneath it.  All you need to do is to modify the Hardness slider in the brush’s attributes pane so as to achieve the desired fading radius.  You can also modify the Opacity setting for the brush, to achieve a similar effect; some experimentation with these two settings (Hardness and Opacity) in the context of a standard paint brush in Photoshop will give you some intuition for how these work in practice.  Yet another option is to use Select > Modify > Feather and to choose an appropriate Feather Radius to give you the degree of fade-out for your selection that you desire.
    Note that you can seamlessly switch between selection tools.  For example, I often begin with the Quick Selection tool, and then switch into Quick Mask mode to refine the selection.  When you go into Quick Mask, any region that’s currently selected will appear red (or, depending on your settings, it may be that regions not selected will appear red—or some other mask color that you have set).  After refining the selection in Quick Mask mode you can leave that mode and then further tweak the selection using any of the other selection tools.  Any selection tool can be set to the “add” or “subtract” mode to allow modification of the current selection, so you can switch between selection tools at will when working on a particular selection.
    In your quest to make the bird stand out from its background, it’s sometimes more productive to concentrate on modifying the background rather than the bird; you might therefore want to select the background, or some part of the background, rather than selecting the bird itself.  When the background consists of a narrow range of colors (a sky, for example), there’s an easy way to select the background which often either gives you exactly the selection that you want or something close enough that you can then modify that selection easily using the tools described above. 



Fig. 10.6.6: Selecting a color range in an
image.  This is often useful for selecting the
background of the image.  Remember that
you can always invert a selection via the
menu option: Select > Inverse.

As shown in the figure above, it’s a simple matter to invoke the Select > Color Range menu option, which then brings up the Color Range dialog box shown below.  The first thing you need to do when the Color Range box appears is to move your mouse cursor out of the Color Range box and to click it on some part of the visible image that contains the color you want to select.  As soon as you do so, all pixels in the image which more-or-less match that color will be selected, and will be temporarily masked out in red (or, depending on how you have the brush color or Invert selector set, all the pixels not of that color may be masked in red).

Fig. 10.6.7: Selecting the background via the Color Range tool.  The Fuzziness
parameter controls how aggressively Photoshop will include other colors similar
to the one you’ve selected.  By holding the shift key when clicking on the image you
can add additional colors to those already selected via previous clicks. 

By turning up the Fuzziness setting you’ll allow Photoshop to also select pixels that are of a color similar to the one you’ve clicked on, with the required degree of similarity being indicated by your Fuzziness setting.  Note that you can also hold down the shift key on your keyboard and click on additional pixels to add to the set of colors that you want to be selected. 


Fig. 10.6.8: The result of using Color Range.  After pressing the OK button, the Color
Range window goes away, and the masked regions (or their inverse) are selected.  In
the example above, you can imagine how much more difficult it would have been to
select the given regions manually, using the mouse cursor.

The reason this tool is useful for selecting backgrounds (especially skies) is that out-of-focus backgrounds often contain a restricted set of colors, which you can rapidly select via this tool.  Once you press OK in the dialog box (or the enter key on your keyboard), the red mask is replaced by a familiar dashed-line selection boundary, as shown in the figure above.  In this particular case you’ll notice that some parts of the background have been omitted from the selection, and a few pixels in the bird have been included; this can be quickly corrected using the Quick Selection tool or the Quick Mask mode.
    There are a number of other things you can do with selections that you might occasionally find useful.  For example, the Select > Modify > Expand and Select > Modify > Contract options allow you to automatically expand or contract your selection by a specified number of pixels in the appropriate direction.  Expanding or contracting the selection in this way can be useful in conjunction with the Feather feature (Select > Modify > Feather), since you may want to feather outward or inward from the selection you’ve already obtained.  Yet another possibility is to convert a selection into a layer mask, which effectively masks out regions of the current layer so that pixels from lower layers can show through.  Layer masks tend to be wasteful (in terms of memory use and file size), but often provide much greater flexibility in terms of being able to make later adjustments.  Layer masks are addressed in greater detail in Chapter 13.
    Another use of Expand and Contract is to rapidly eliminate large numbers of tiny “holes” in your selection, such as may occur when selecting via Select > Color Range.  Rather than sweeping these little “holes” out via a selection brush, you can simply Expand by some number of pixels and then Contract by the same number of pixels.  This should close up any holes of sufficiently small diameter, without too drastically altering your selection otherwise (though it will tend to smooth your selection boundary).  Along a similar vein, beware of tiny “islands” of selection that may remain after you deselect a region that the Quick Selection tool incorrectly selected; these little islands of selection may escape your attention when you’re creating the selection, but later can become more obvious if drastic exposure adjustments are made to the selected pixels.  Checking for these superfluous selection islands can be done by (temporarily) creating a layer mask for the current layer from the selection, and then holding the Option / Alt key while clicking on the mask with the mouse cursor; this will display the layer mask at high resolution in the main image area, so you can check for small islands of black pixels representing selection islands that you don’t want.  Alternatively, you can simply Contract your selections by some small number of pixels (say, 10) and then Expand by the same number, to ensure that features smaller than this diameter will be automatically deselected.
    It’s worth keeping in mind that for many applications you needn’t obtain the most perfect selection that separates, with 100% accuracy, pixels of the bird from the non-bird pixels around them.  Though sometimes it’s possible to obtain nearly perfect selections using the Quick Selection tool, in many other cases you’ll find it requires rather more work.  For images that you intend to print on large media, it may indeed be worthwhile for you to magnify an image to 100% zoom and then spend the time painstakingly adjusting the selection boundary to achieve perfect separation between the bird and non-bird pixels.  For images to be posted on the internet, this is rarely necessary.  Even for images to be printed large, imprecise selection is often still acceptable, especially if you’ll be feathering the selection anyway.  For bird photographers who take thousands of images at each outing, imprecise selection during postprocessing is a matter of practicality.  Many of the transformations you’ll apply to a selected region (such as sharpening or de-noising) can be done using only quick-and-dirty (i.e., imprecise) selections.  Knowing which selections need to be precise is something that will come to you with practice (as will knowing how much feathering to apply, and related decisions).  Just keep in mind that when processing the bird separately from the background you’ll want to make sure that no part of the selection extends beyond the actual boundary of the bird.
    Note that once you’ve selected part of an image via the selection tools, you can then apply just about any processing filter in Photoshop to just that part of the image.  For example, if after selecting the bird you then invoke the Hue/Saturation window, you’ll find that the adjustments you make in that window will affect only the bird (or any other part of the image which is currently selected).  As we’ll see later, this is an extremely powerful and efficient technique for improving the aesthetics of an image.
    Finally, note that the decision of whether to apply filters to a selection directly, or to first convert the selection to a layer, needn’t be an “either-or” proposition.  Because creating and deleting (or merging) layers is so quick and easy in Photoshop, it’s often convenient to go back and forth between them as needed.  What I typically do is as follows.  First, I create my selection, usually using the Quick Selection tool.  I then save the selection to a named channel (Select > Save Selection).  The selection stays active after saving it, so I can simply press Cmd-J on my Macintosh to make a layer out of the selected pixels.  The selection goes away at that point, so the “marching ants” (dashed line indicating the selection boundary) are gone and will no longer distract me.  I then invoke the desired filter to bring up its parameter window, and make sure the Preview box is checked, so that the effects of parameter changes are updated instantaneously.  With the marching ants out of the way, I can concentrate more easily on the overall aesthetics of the image and how my impression of the image changes as I move each parameter slider.  Once I’ve finished setting the parameters and have applied the filter, I then merge the temporary layer back into the underlying layer that it came from (by right-clicking the mouse on the layer in the Layers panel and selecting Merge Down, Merge Layers, or Merge Visible, as appropriate). 
    If  later I decide the same region needs additional processing, I can easily call up the same selection via Select > Load Selection and then proceed according to the same series of steps.  By not keeping these temporary selection layers around indefinitely, I’m both saving memory and disk space and also keeping the Layers panel uncluttered.  This also avoids the potential for confusion later: keeping too many layers can complicate further processing, since you need to put more mental effort into keeping track of which layers are on top of which others, and which layers you want to select from, when making new selections.  With saved selections, you can re-create a layer for a selection at any time, as needed. 

*If you double-click the Quick Mask icon you should see a dialog box containing a number of parameters, one of which allows you to use black or white as the masking color rather than red; you can also dictate whether the painted regions, or, alternatively, the unpainted regions, are to be selected when transitioning out of Quick Mask mode.