Simple Color Enhancement in Photoshop with Lab Color Curves

Have you ever taken a photo of a particularly stunning sunset or vibrant autumn leaves only to get home and find that the colors are just not quite as bright as you remember them? Well, there's a good reason for that.

Without being too technical, the primary colors of light are red, green, and blue (as opposed to the primary colors of pigment which are cyan, magenta, and yellow). Thus, your color TV, your laptop's LCD, and the HD Jumbotron at Auburn University's Jordan-Hare stadium (war eagle) all use red, green, and blue lights to display any color they want.

So, it stands to reason that when your camera's CCD gathers raw data in red, green, and blue channels that your camera would store the data in RGB format. The problem is, though, that your brain is a little more complicated than this. Your brain adds expectations based on light, shadows, and past experience. So, when your pictures don't look like you remember, that's because the camera doesn't know what your brain said it should look like.

There's an App for That

The good news is that this problem was solved way back in 1931 when the International Commission on Illumination came up with the CIE 1931 color space. This color space has been expounded upon through decades of experimentation and is now generally called Lab (the L stands for lightness; a and b stand for two color-opponent dimensions (long story). This color space was designed to mimic the color distributions of human perception.

What does this mean for you? Well, simply put, you can easily adjust your images using a curves adjustment layer in Photoshop. Before I show you how, let me show you a few samples.

Demonstration

These images have been color enhanced leveraging the Lab color space. To see the original picture, just hover over the image with your mouse cursor.

Using Lab Color Curve Adjustment

You can make Lab adjustments with gimp and there's a Paint.Net plugin too. I may publish instructions for these applications if more people start using them, but here's how you do it in Photoshop.

Here's how you do it:

1. Open your image
2. Click Image >> Mode >> Lab Color
3. Click Layer >> New Adjustment Layer >> Curves
4. Name your layer and click OK
5. Adjust the curve for channel a
   
   1. Drag the top right corner in one quarter of the way
   2. Drag the bottom left corner in one quarter of the way
   3. If you did it right, the window will look like this:
      
6. Repeat the process for channel b
7. Press Ok
8. Click Image >> Mode >> RGB to convert it back to RGB color so you can save it

That's it! Now, disable the adjustment layer and then re-enable it a few times to see the difference it makes. When you're ready to save your image, merge the visible layers and save a copy of your image.

Homework

Once you've got the hang of it, you'll be able to get much more real life color out of your images. As usual, we'd love to see what you have so your homework is to apply this effect to some of your own images. If you see any dramatic results, post them on Picasa or Flickr. Leave us a comment and link to your images. If you see any pictures you think are better without the color enhancement, we'd love to see those too.

Time Priority (Shutter Priority) Creative Mode

Having completed the introduction to the basic shooting modes in Getting to Know Your Shooting Modes, we're ready to take a look at our first creative mode called Time Priority or Shutter Priority. The indicator for this shooting mode differs from camera to camera and your best bet is to read your manual for your device; however, generally the time priority setting is identified as Tv on Canon cameras or S on Nikon and Sony.

As you probably know, the camera has two ways to control the amount of light that contacts the sensor (whether it is film or digital): shutter speed and aperture. Aperture refers to the size of the opening in the lens and we'll talk a lot more about aperture later when we talk about Depth of Field and portrait photography, but for now just know that your exposure is set primarily by shutter speed and aperture setting.

The time priority shooting mode allows you to chose exposure time and the camera will set your aperture for you. This way you can concentrate on how you want motion to appear in your photograph without having to worry about getting the right exposure. In the demo photo above, you can see two different effects you can make with shutter speed.

What's it for?

One thing you might want to do in your photo is capture the feeling of motion in your photo. In the waterfall photo, we wanted the viewer to be able to feel the intensity of the water as it rushes over the smooth rocks and crashes into the pool below. We decided to keep the shutter open longer to let the motion blur of the water appear giving the image the look and feel of being in motion.

Another thing you might want to do is freeze time stopping all motion to record an exact moment in time. You might want to catch the exact moment a balloon pops or a water droplet hits the ground. In the demo, we set the shutter speed to about 1/2000th of a second to freeze the rapidly fluttering wings of a hovering hummingbird.

By the way, this is how two of the basic modes work. Sports mode increases your shutter speed (decreases exposure time) to about 1/500th of a second in bright light to stop motion and give you a clear crisp shot of all the action. Night mode decreases shutter speed (increases exposure time) to gather as much light as possible from the background of the night shot. The night shot will also enable the built in flash (if your camera has one). There's a good reason for this; however, we'll be discussing that in a future lesson all about using the flash.

Finally, a long exposure isn't always just for showing motion. Sometimes, a long exposure can bring out a lot of subtle details. For example, a long exposure can help you bring out the vibrant colors of a sunset or sunrise. Just keep in mind that longer exposures will require a tripod to keep them clear. A good rule of thumb is 1 / focal length so if you're shooting at 100mm (effective) then you'll need a tripod for any exposure longer than about 1/100th of a second.

Homework

With that, you have another homework assignment. Set your cameras on Time/Shutter priority and go get some pictures. Put your camera on a tripod (or on anything stable really) and take the same picture twice: once with a fast shutter speed and once with a slow shutter speed. What do you notice about the motion of the objects in the picture? Do you notice anything about the feeling that's conveyed in each? Is there any difference in the colors and clarity of each of the pictures? What happens to the aperture setting (f-stop) as you change your exposure time?

Try taking a bunch of handheld shots at different exposure speeds. What's the slowest shutter speed you can use and still get a crisp image? What if you use a tripod?

Take some long exposure night shots. What could you do if you wanted to freeze the action at night? If you want some advanced homework, go out with a friend and try to get some night portraits. What do you notice about objects in the foreground? Try using the flash and a short exposure time. Now, try using the flash and a long exposure time. What happens? Why?

Be sure to put your answers in the comments and share your favorite photos on Picasa or Flickr. Please let us know what you think of our blog and what you'd like us to write about in the future.

The best way to learn is to teach. If you have an idea for a class, write it up and send it to us. If we like it, we'll post it. Be sure to include your name and a link to your organization and/or portfolio.

The Photography Professors