It takes just a few clicks in Photoshop to elevate print images from good to amazing, reveals Marshall Atkinson
Many creative digital artists struggle with Photoshop because there are simply too many options to choose from when adjusting the image; they simply don’t know the tools or get caught in a rut when processing their files.
What if I told you there was some secret Photoshop magic that’s easy to use, has only two steps and takes two minutes or less to get to amazing results? Meet the LAB channel. It’s a very powerful image colour space in Photoshop that can save you hours of time tweaking your files for print.
RGB to start
Here’s how it works. We are going to start with our image in RGB – the red, green and blue channels and the traditional additive colour space (meaning that the three colour channels added together form the basis for the total colour gamut). LAB uses that same colour space, but divides it up into three completely different channels: Lightness, A and B. The Lightness channel is simply the luminosity or the greyscale, if you will, of the image. The A and B channels are all the colours of RGB, but just divided into two colour channels instead of three.
There are a few things we can do immediately that will improve any image and save you hours of time. The first is tweaking with some simple curves with an Adjustment Layer, and the second is using an Unsharp Mask step.
Before we get too far into this, I want you to open a photo in Photoshop and play along. Use one that’s a raw file and unprocessed or not improved yet. Learn by doing, it’s the only way.
Don’t screw up a file you need though. Open something that you can use, and then make a copy of it. Save it as ‘LAB Test’.
LAB colour space
Next, convert your image to the LAB colour space. To do that, just click ‘Edit’ on the top menu and then choose ‘Convert to Profile’. From the dialogue-box drop down, choose ‘LAB Color’.
You won’t see any immediate change to your image, but you are now poised like a Photoshop ninja to strike and make some fantastic improvements.
Third, create a curves Adjustment Layer. Just click on ‘Layer’ from the top menu, and choose ‘New Adjustment Layer’ on the pull-down, then ‘Curves’. Click ‘Ok’ in the box that pops up. This step creates a new layer in the file so you can toggle back and forth and review your handiwork as you change the image. You could skip this step and just alter your original file layer without it, but that’s like working without a safety net. But if you’re like living dangerously, or just love the History tool, then skip away.
Now comes the fun part. There is a drop down menu near the top of your Adjustment Layer. Click on it and you will see three choices. L Channel, A Channel and B Channel. To start, click and select the A Channel. (If you aren’t using the Adjustment Layer, just do the steps below by choosing Command M and go to ‘Curves’.)
The Photoshop Histogram will appear. If you normally use this tool, it will look dramatically different from what you usually might see, as the graph will show a huge spike the middle. That’s normal in LAB mode. For our exercise, we are just going to adjust the endpoints of the Histogram graph. Simply click and drag the black endpoint of the diagonal line in the graph until the input number reads -90. Now do the same for the white endpoint, but you want 90 instead. Your input numbers should be the same, but because they are on opposite ends of the graph, one will be negative and the other positive.
Don’t worry about what your image looks like at this point, because it may look a little weird as you’ve only finished half of the correction. We’ll need to adjust the B Channel next to balance everything out.
Go back to the Adjustment Layer drop down and it currently shows the A Channel. Click on the drop down and select the B Channel. Repeat the above steps for the B Channel, with -90 and 90 as the new input numbers for black and white respectively. Abracadabra: your ninja Photoshop magic has struck!
Now check out your results by simply toggling your Adjustment Layer on and off. Your image should look dramatically better, similar to the right side of the photo of the tiger (Figure 1). What happened is that you’ve globally increased the colour range of the image. I always use -90/90 to start, but if your image still needs some tweaking go back and adjust your Histogram with more or less depending on the results you want and the image you have.
Once you get good at this step, you’ll find it is a great starting point for any Photoshop file you are working with. For images that already have rich colours, you won’t see much change, but if your file is muddy it will make an incredible difference. This works great with any image sourced from a camera phone, especially if the overall image looks grey and flat.
Unsharp Mask zing
While you are still in LAB mode, click on the ‘Lightness Channel’ to select it. Then go to Filter and click ‘Sharpen’, then choose ‘Unsharp Mask’.
Because you are working in the L Channel, everything you do only affects the luminosity of the image, not the colour. Making adjustments to this layer, independently of the colour, greatly affects the ‘pop’ of the image. For screen or digital printers, this will become your new secret weapon.
The reason this matters so much is that T-shirts are essentially printed billboards. Viewers only have a few moments to get the full impact of what they are seeing. Adding a little zing to the image can boost its appeal to the viewer. This effect works wonders with textures, tiny details and patterns.
Check out the tiger again. What gives the fur and whiskers the extra dimension is this Unsharp Mask step. Compare the left and right side of the tiger photo. That’s about thirty seconds of effort, maybe less. I probably did it a little too much, but I was trying to make a point.
In the Unsharp Mask filter, there are three sliders you can adjust. ‘Amount’, ‘Radius’ and ‘Threshold’. For ‘Amount’, the more you slide the selection the right, the more intense you will alter your file. The ‘Radius’ selection simply grabs and combines the pixels in an area, so the more you slide the selection to the right, the bigger image grab you’ll get. ‘Threshold’ works a little differently, as the more you slide to the right, the more greyscale levels you are selecting at one time, so the effect is minimised as you slide.
The only way to learn what happens is to just play with each until you are satisfied with the cumulative effect of your choices. What will happen is that the bright white and deep black parts of the image will increase in intensity the more you use the sliders. Textures such as hair, woodgrain, feathers, corrosion, crinkles, and crevices, and any highlighted or deep shadowed areas, will suddenly bounce in the image. Remember, this doesn’t affect the colour. Be careful though, like adding salt to a recipe you can go too far and ruin the result. Unless of course, that’s the craziness you want.
Once you are satisfied with the results, click ‘Ok’. This Unsharp Mask step can save you hours of time by not having to use the Dodge and Burn tools at all in your image. Just be sure to revert back to RGB mode and continue your separations or work for production.
When you get the hang of these two steps, you can easily adjust any image in two minutes or less and tremendously improve how they will perform for printing. Another great thing with this process is that the file has been changed on a macro level, but with details intensified on a micro scale. All without selecting any area, using any other tools, or any wasted time.
Marshall Atkinson is the Professional Services director for InkSoft, and program owner for the new InkSoft Production Manager software. In his Professional Services capacity, Marshall provides coaching to shops on operational efficiency, continuous improvement and workflow strategy, business planning and strategy, employee motivation and management and sustainability.