As part of our ongoing efforts to showcase some of the fun effects you can apply with photoshop, we're going to touch on how to selectively desaturate an image.  There are multiple ways to achieve this type of effect; each method involving the utilization of Photoshops massive tool box to do the work for you.  We’re going to go over a couple of different ways to selectively desaturate, but first, what does that even mean? 

‘Saturation’ is a term used to describe the intensity of basic colors that make up an image.  As such, the lower the saturation of the image, the less intense the colors.  When an image has no saturation at all (see: desaturated) , it becomes a black and white image.  ‘Selective saturation’ usually involves converting an image into black and white, with the exception of a single part of a photo that remains in color.  Often, the part of the photo left in color is the primary subject.

Thousands of photographers have used this technique, with varying degrees of success, for a long time. We won’t claim that our example here is going to be high art, but it should serve as a nice guide. 

As in our previous tutorial , we will be achieving this effect by shooting our subject in natural light.  Unlike our previous tutorial, however, this affect can be achieved by shooting in a controlled light environment, so if you’ve got some off camera strobes you’ve been itching to fire, feel free to bust them out!

For this tutorial, we will be shooting a sleek Lotus Elise, parked right outside our offices.  Because the majority of this tutorial has to do with Photoshop, we won’t spend too much time going over your camera settings.  The car I’m going to be shooting is bright orange, a perfect color for this type of project.  When shooting, however, keep in mind that you want your subject to be much more bold than usual.  As such, I recommend taking a good light reading, then knocking your shutter down one or two steps to really get that color to pop.  Doesn’t have to be too dramatic; remember, you’ll have a chance to tinker with your light settings later in Photoshop. 

Once you’ve got an image that you feel will work, upload it to your computer and open up Photoshop.

The quickest and easiest way to go about doing this involves creating a copy of your current layer.  Click over your image in the Layers Palette on the bottom right hand corner of the screen.  Right click the picture, and select Duplicate Layer. 

 This will create two identical images, one on top of the other.  You may already see where I’m going with this.  Select the top layer in your layers palette, go to Image, and hit Desaturate.  You now have a black and white picture laid directly over a colored picture.

This essentially means that if you were to grab your eraser tool, you could erase away the black and white image leaving the colored image below.  Though this may sound easy in concept, it’s extremely easy to botch such a method, mainly because if you accidentally erase outside of the car, the color will spill over. 

In order to counteract this and keep your image looking as professional as possible, I will be covering two easy ways to selectively desaturate any focal point in an image.  Both of these methods can produce a professional looking photo, and can both be done quickly and efficiently with some practice.  

1.  Layer Masking 

Understanding the uses of layer masking can be an integral part in understanding the basic concepts of PS.  In this case, we have a desaturated ‘layer’ covering over the original saturated image.  By using a layer mask, we can choose which parts of the mask we would like to change, and which parts we would like to remain the same.  

In the instance of this tutorial, we want to keep a black and white, desaturated background, but we’d like to bring the colored car in from the picture beneath.  To do this, select your Layer Mask tool on the bottom right hand corner of the screen.   This will create a mask over your top layer that will appear as a white box. 

 

Make sure to select the white box¸ as you will be drawing on this mask to achieve your desired effect.  

    

Once you’ve selected the white box, select the brush tool (B), set its opacity and flow to 100%, and choose a nice, large, solid brush.  Begin painting over your car.  You’ll notice that your brush isn’t simply swiping black strokes across your canvas; this brush is bringing the color back into the car!  Keep in mind, however, that painting outside of the car will cause the color to bleed out; a common issue that can ruin the effect.  For the time being, however, don’t worry about the spillage.  Grab a huge brush and just paint around the general area of the car so that the whole vehicle is properly colored.  One of the benefits of a layer mask is that we can go back and touch it up afterwards.  

After taking a huge brush to the photo and painting on the layer mask, I came away with something like this.

You’ll notice that the car is fully colored, but so are segments of the surrounding background.  Layer masking offers a simple solution to this problem.  Reselect your brush tool.  Hit ‘X’ on your keyboard to alternate your back/fore ground colors, and switch to a white brush.  When layer masking, a black brush unveils the image below, but a white brush fights to keep the image black and white.  Zoom in on your image, and lower the size of your brush.  With your new white brush, carefully paint away the color that has bled over.  If a particular segment is giving you trouble, zoom in even closer and/or choose a smaller brush.  Also keep in mind that alternating between a white and black brush while layer masking is key to selective desaturation with layer masks. 

After carefully brushing away at my car, I came away with this. 

You’ll notice slight errors on some of the corners of the car.  This can be easily corrected by switching back to a black brush ‘D’, zooming way in, and correcting the mistakes. 

You can zoom nearly infinitely with Photoshop, so don’t be afraid to realllllly get in there to correct your colors.

After a couple of minutes of touching up, this is what I came away with.  

Remember, when using layer masks to achieve this effect, alternating between black and white brushes and exercising patience is key.  

2.  The Pen Tool  

The Pen Tool can be a little daunting for people upon initial use, but learning to master it can truly open a lot of creative doors for future projects.  The pen tool allows you to accurately trace nearly anything.  The importance of a thorough trace?  Well, if you’ve got a situation like this one, a proper trace will ensure you ‘color inside the lines’ so-to-speak.

The pen tool works a lot like a connect-the-dot puzzle.  Put your cursor where you’d like to begin and click once.  A small square will appear.  Your next click will connect that initial square to another square, and so on.  You’ll notice, however, that the line between each of the squares is straight, which in turn makes it quite hard to trace a car (or any object) with curves.  

In order to get the hang of using the pen tool, open this image.  (Note:  If you’ve already had experience using the pen tool, skip ahead a couple of paragraphs, as this will simply cover the basic concepts.)  We’re going to try and make an accurate outline of this pen.  In order to do, let’s start around the middle, just underneath the cap.  Select the pen tool and make your first selection.  Since you’re connecting your points in a straight line, scroll along the length of the pen and connect your first two points by simply clicking once.  Continue towards the end of the pen.

 

 

 

Uh oh.  Now we have a problem.  The tip of the pen is curved, and the pen tool only seems to connect in straight lines.  We’re going to have to curve the line.  How is this done?  First, draw and connect two points from the one side to the other, as shown below.

Every line drawn by the pen tool can be curved or warped in any way you see fit.  In this particular instance, left click the center of the line you’ve just drawn to create a new point in the middle of the line.  Now hold CTRL to access your pens warping tool.  This should change your icon from a pen icon to a mouse icon.  Grab that middle point, and pull it outwards so it properly warps to fit the curved end of the pen.  You’ve just curved your first line! 

 

 
Just to make sure you’re getting it, let’s finish the trace. 

We’ve pretty much got a straight line from here to the edge of the pen cap, so go ahead and punch that in.   

You’ll notice in my example that I slightly overshot, and that the back end of the trace cuts a bit of the pen off.  Again, this can be addressed easily with your pens warping tool.  I selected a nice middle point, and simply pulled the trace slightly down to accommodate the shape of the pen. 

Now we’ve reached the end of the cap, with another curve we’re going to need to trace.  This will be done exactly the same way as the opposite end. 

Draw a straight line from bottom to top, select a middle point, hold CTRL, and pull that point outwards to create a curve. 

Now that we’ve got an accurate trace, close the ‘path’ by reconnecting your final point to the one you started with.  You’ll know your path has been complete when a small circle appears next to your pen icon. 

 

That wasn't so bad was it?   Now that you know how the pen tool works, lets see how we can easily apply this to our selective desaturation tutorial! 

Like before, open the image you would like to use in Photoshop.  Duplicate the layer, and desaturate the newly created layer.  Again, you now have a black and white photo over a colored one.  This time, we're going to use the pen tool to 'select' the car in the image, which will drastically speed up our coloring process and do away with the need for all that touching up we experienced with the layer masks.  Select your car the same way you learned to select the pen (the actual pen, not the tool...I just realized how that could be confusing).  Trace slowly and carefully, and curve lines where you need to.  My trace looked like this (seeing the trace is kind of hard, click the image to enlarge). 

 

Remember, the accuracy of your trace is entirely dependent on how much time you're willing to spend on it.  Zooming in and curving correctly are very important, so take your time, and don't be afraid to step backwards (ALT+CTRL+Z) if you make a mistake!  

Now that you've got your trace, here comes the fun part.  Head over to your Paths tab on the right hand corner of the screen.  Here you will find a tiny image of your trace. 

Right click the image,and click on Make Selection.  This option allows you to take any trace you may have in an image, and select it.

Don't mess with any of the settings in the pop up screen, simply hit 'OK'.  You will now have a flashing line selection drawn around your main subject.  

 

 The main point of selecting anything in Photoshop is to focus the program on that selection and nothing else.  Think of making a selection as setting boundaries that can't be crossed, no matter what.  Since you have a selection of a black and white image over a colored one, and you want the car in color, maybe it's time to grab the eraser tool (E).  Select a nice, big brush, and make sure your opacity is set at %100.  Now begin erasing your top layer away.  Because the car is selected, it's impossible to erase outside of the boundaries you created!   

When you're finished, hit CTR+D to deselect your subject, and have a close look at your colored subject.  The more time you spent outlining, the less imperfections you'll find.  Still, as with layer masking, if you do notice any parts you may have missed, zoom way in with your eraser and fill them out.  

As selective desaturation is often used for commercial photography, I've added a little pizazz to the final image and came up with this: