Basic enhancement in Photoshop
Basic photo enhancement using Lab in Photoshop

Enhance photos easily in Photoshop with Lab

Lab is a powerful color mode for color correction and enhancement within Adobe Photoshop. Combined with Curves and Channels you can easily enhance photos very quickly. In this tutorial I’ll show you some basic steps to take. If you want to follow along here’s the high resolution photo I’ll be using.

Flower for Basic Enhancement
High res original photo for Flower for Basic Enhancement in Lab Colorspace

How to bring out color and depth using Photoshop and the Lab color space

 

Step 1:

Start by switching the color mode to Lab (Wiki).

Lab is pronounced letter by letter as L, A, B similar to how you spell out CMYK or RGB. The L stands for Lightness, a and b don’t stand for anything but each contains color information. The a channel contains the Green and Magenta, while the b channel contains the Yellow and Cyan. In that sense you can think of it as a very powerful Tint and Temperature if you come from a Photography background, much much more powerful though. The Lightness channel is a black and white channel, which is similar to an Alpha Channel. This is where your contrast and detail exists. This separation is part of what makes Lab so powerful. If you’re not familiar with Alpha Channels, that’s fine. I’ll be covering that in another tutorial.

Step 2:

Now we’re going to create a new Curves Adjustment Layer. Be sure to use an Adjustment Layer either by clicking through the Layer Menu or Layer Panel. We want to be able to work non-destructively and fine tune things so this is a better workflow generally than doing Image Adjustment Curve. Once the Curve Properties is open if the grid is the larger size squares (the default) then hold Alt and left-click to get a tighter grid.

Now leave the L channel and switch to the a channel in the second drop down. Then move the top right in 3 squares, you’ll see a heavy Magenta color cast. When we move the bottom left in 3 squares, you’ll see it go back to neutral. This is a great way to create or fix color casts if needed. Now switch to the b channel and move each of those in 2 squares.

Lab Color Enhancement Curve
fig 5-1 Basic Lab Color Enhancement Curve

I like to go at or just beyond where I want it cause then I’ll refine by lowering the opacity of the Curves Adjustment Layer. In this I like it around 60% opacity. Also be sure to rename the layer something meaningful, Color Enhancement or Color Pop or something of that nature. Here’s where we’re at:

Flower after basic color enhancement curve
fig 5-2 Flower after initial color enhancement

Step 3:

Now that we did the color, let’s work on the contrast. Because our focal point is the flower in the middle, and it resides primarily in the Midtones we’ll use a Luminosity channel to easily mask it.

To create the midtone Luminosity Channel go to your Channel panel.

  • Duplicate the Lightness channel. Invert that Channel with Ctrl+I. Rename that Darkness. In other images you might find use for this channel, but we want the Midtones. To get that we’re going to intersect the Lightness with the Darkness.
  • Hold Ctrl and click on the Thumbnail next to Lightness channel so it creates a marquee on it.
  • Hold Ctrl+Alt+Shift and click on the Thumbnail next to Darkness channel (you should see a tiny X by the cursor). A Warning will appear that not enough pixels are selected, click okay – they’re selected I promise!
  • At the bottom of the Channel panel click on Save Selection as Channel. Rename this Midtones
Channel Panel with a Darkness and Midtone Channel
fig 5-3 Basic Lab Midtone Channel
  • Hold Ctrl and click on the thumbnail next to Midtones then click back to Lab
  • Go back to your Layer panel and create a Curves Adjustment Layer, it will have the Midtones as a layer mask. Congrats!
Curve with Midtone Mask
fig 5-4 Curve with Midtone Mask

Step 4:

With our mask in place, let’s adjust the contrast. In our Curve’s L Channel we’ll add a pretty steep S-Curve, a steep segment from bottom left to top right is more contrast. This is because the left side of the Curve is your darks while the right side is the lights. Lowering the darks and raising the lights increases contrast. Thanks to our Midtone Mask we can apply this pretty heavy handed without worrying about the leaves and background being affected much.

Hard S-Curve for contrast
fig 5-5 Hard S-Curve for contrast

Now to refine hold Alt/Option and click on the Mask and you’ll enter into it. Then hit Ctrl+L to pull up levels and you can tweak it to even further isolate the flower from the leaves as you see fit.

 

Levels on Midtone Contrast Mask
fig 5-6 Levels on Midtone Contrast Mask

Rename the layer and adjust the opacity to your taste. Mine in this instance is around 40% opacity. Now we’re at this:

Basic Lab Enhancement after Contrast
fig 5-7 Basic Lab enhancement after Contrast

Step 5

Finally, we’re going to sharpen this a little using High Pass Filter.

  • Duplicate the background layer
  • Rename it Sharpening
  • Convert the Layer for Smart Filters
  • Apply High Pass Filter (Filter > Other > High Pass) to taste. I used 4.6
  • Change the Layer Blend Mode to Linear Light
  • Since we used Smart Filter we can refine with either Opacity or adjust the High Pass again. I left the High Pass at the 4.6 but lowered the Opacity to 32

At this point it looks pretty good. You might notice edges are a bit harsh though. You can easily refine this using a Layer Mask on the Sharpening and a brush set to a light flow. There are other ways to do this using Luminosity Channels but for this image I’ll just use a Brush to do it. Notice on the top, pre-mask, how the highlights on the edge look overly bright, that’s what we want to dial down with a mask as you can see in the bottom half of the screenshot

Basic Lab Enhancement Sharpening
fig 5-8 Basic Lab Enhancement Sharpening

Conclusion

That’s really all there is to it. To recap:

  1. Color bump by bringing in the a channel and b channel in a Curve Adjustment Layer
  2. Contrast bump using an S-Curve on the L Channel which we isolated with a Luminosity Mask for midtones
  3. Sharpness bump which we did for this one using a High Pass Filter
Flower for Basic EnhancementBasic Flower after Lab Enhancement

You can see how this quickly adds a lot of depth and color to an otherwise flat photo in a very short amount of time.

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