As I am sure you know, digital images straight from the camera can lack a little sharpness. You probably also know that in the menu system of your camera, there are various options to sharpen the image when you take it. For run-of-the-mill snapshots, these in-camera sharpening techniques are fine; however, if you are looking to print your images in a large format, you need to dial down your in-camera sharpening. Better still, shoot RAW, and then use Photoshop to create a much higher-quality sharpened image.
There is one major caveat to sharpening images in any post production software, and that is that you cannot make a soft image sharp. If you have camera shake or poor focus in an image, you will not be able to fix that; only work from images that are inherently sharp but need further sharpening to ready them for output.
Whilst Photoshop has several built-in sharpening techniques — Unsharp Mask, Smart Sharpen, etc. — there are a couple of more advanced techniques that can really make your images pop, namely High Pass and Lab Color sharpening.
Image sharpening should be the very last thing you do to a digital photograph before outputting it in its final form. You should make all adjustments — exposure, color, curves etc. — first, then save the image. Next, you need to resize it to the desired output size, and save a new version of it. Finally, once the image is fully ready to go, only then do you apply the sharpening. You need to be careful not to overdo it when applying any type of sharpening. An over-sharpened image can look awful, and is characterized by artifacts, particularly in areas of high contrast.
The original shot
The original shot at 100%
Let’s have a look at the two advanced Photoshop sharpening techniques for getting really sharp images.
Lab Color: With your image open in Photoshop, the first thing to do is convert it to Lab Color Mode. At the moment, it is probably RGB 16-bit or 8-bit. To get into Lab Color, from the Photoshop menu at the top, go to Image – Mode – Lab Color.
Select Lab Color
Visually, nothing will appear to have happened, but if we go to the Layers palette on the right side of the screen and click the Channels tab, we will see, instead of RGB, Red, Green and Blue; Lab, Lightness, A, and B. Select the Lightness channel, and you will see the image turn black-and-white and will zoom your image to 100%
Pick the Lightness Channel
Now go to the Photoshop menu and select Filter – Sharpen – Unsharp Mask. A new window dialogue will open showing three sliders: Amount, Radius and Threshold. Use combinations of these three sliders to control sharpness, with Amount being the primary control. Radius works well with a setting between 1 and 2, and increasing the Threshold reduces the effect of the sharpening. An ideal setting for this is between 1 and 3.
Unsharp Mask in Lab Color
Increase the Amount control until you are happy, being sure to look for artifacts in the image and backing off a little if you find any. If you have used Unsharp Mask before in normal RGB mode, you will notice that you can apply a much higher amount of sharpening in Lab Color. When you’re happy, click OK. Now we return to Image – Mode and select RGB. You should find the result is a nice, sharp, punchy image.
High Pass Sharpening: this is a touch more complicated but potentially even more effective. With our image open, we are going to make a duplicate layer from it. From the Photoshop menu go Layer – Duplicate Layer.
We will see our new layer appear in the Layers palette on the right of the screen. Make sure the duplicate, upper layer is selected and change the blend mode from Normal to Overlay.
You will notice a big increase in the image contrast. Now select Filters – Other – High Pass. In the window that opens you will see an “embossed” version of the image and at the bottom a slider for Radius.
High Pass Filter
Move the Radius slider left or right and keep an eye on your main image as well as the embossed image. Sliding to the right increases sharpness and sliding to the left decreases it. A good starting point is a radius of 2. Use a combination of the main image window and the High Pass window to judge the correct sharpening amount. When you’re happy with the effect, click on OK. You can further adjust the amount of sharpening by changing the blend mode to Soft Light or Hard Light, or by backing off the duplicate layer’s opacity.
The final result
Sharpening is a vital part of any image post production, and when done well can add dimension and contrast to an image. With either of these two techniques, you should be able to create punchy, sharp images that will look great in a large-format print.