As I am sure you will know, digital images straight from the camera can lack a little sharpness. You will also know that in the menu system of your camera there are various options to sharpen the image as you take it. For run of the mill images that are not important, these in camera sharpening techniques are fine, however if you are looking to print your images large format, you need to dial down your in camera sharpening, or better still shoot RAW, then use Photoshop to create a much higher quality of sharpened image. There is one major caveat to sharpening images in any post production software and that is that you cannot make an unsharp image sharp. If you have camera shake or poor focus in an image, you will not be able to recover that, only work from images that are inherently sharp but need further sharpening to ready them for output.
You can download the original Jpeg for this tutorial here
When To Sharpen Your Image
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 for it’s final use. You should make all adjustments, exposure, color, curves etc, first, then save the image. Next you need to resize it to the output size and save a new version of it. Finally once the image is fully ready to go, only then do we apply the sharpening. You need to be careful when applying any type of sharpening not to over do it. An over sharpened image can look awful and is characterised by artefacts, particularly in areas of high contrast.
So let have a look at the two advanced techniques for getting really sharp images.
Sharpening With Lab Color.
With your image open in Photoshop, the first thing we are going 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 Image - Mode - Lab Color.
Visually nothing will have appeared 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 will turn black and white and zoom your image to 100%
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. We use combinations of these three sliders to control sharpness 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.
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. Once 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 Technique
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 from 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.
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 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. Once happy 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 of the duplicate layer’s opacity.
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.
For those of a more visual bent, I have produced a video on how to do this.
You can download the original Jpeg for this tutorial here