Post date: November 6th, 2010 | Category: Photoshop Tutorials & Tricks, Prepress tricks

Advanced Photoshop Sharpening

Sharpening a digital image is one of the oldest techniques used in the industry of imaging. It looks like it’s purpose is clear as we hear how it’s called, but, this filter can be used for much more.

OK, not that we can jazz up totally blurry low cost surveillance camera images (like on CSI, right?), but we can enhance a lot more then just adding more sharpness to our images. In some cases, if the “essence” of the photo is there we CAN perform miracles.

In this tutorial, I shall take your Photoshop sharpening skills up to the next level! With introducing some tricks I discovered you can master this simple but very handy tool.

Let us first analyze the opposite of sharpness: in order to “understand the light”, we must also “experience the darkness”. I’ll provide examples using Photoshop, but you can also use Gimp, as it also has very similar filters.

Image Sharpness vs Blurriness

The blurriness of the images comes from various factors: camera lenses, non-professional scanners, shaky hands or too much alcohol in the blood. All of these factors can be somewhat reversed, if not totally. Let’s analyze what characteristics and parameters does a naturally occurring blur have.

We have the radius of the blur, or the direction and speed if it is a motion blur, and the intensity of the blur. Camera lenses have distortion, dispersion of light and blur effects. If the camera is digital, it will also have some blur due to the color sensor array and the software within the camera. If you are scanning slides, the scanner will also introduce a blur.

How do we fight these? Well, here comes the handy Photoshop’s sharpening filter plugin!

Light Dispersion and Lens

Camera lenses and the mechanism of refracting light to the film or the photo sensitive sensor is imperfect. The cheaper the lens, more profound this effect is. With light dispersion effects we usually get a light “dreamy” effect, something similar to a fog. These have a characteristically large radii and small intensity blur. This is not visible to an untrained eye, but once you start noticing this, you will immediately know what to do to solve the problem.

In the following examples I used a large radius Photoshop sharpening filter to the image on the right side. I also exaggerated a bit so you get a clearer picture of what is going on.

Original image

Example of Photoshop Sharpening with large radius

The left original image may look just fine, but let us play with it a little.

Using Photoshop’s Smart Sharpen filter enhance this image by applying these settings:

Amount: 30%
Radius: 60 px
Remove: Lens Blur
More Accurate: On

Note that these parameters are valid if you are using it for the example image. A larger original image would need proportionally larger radius for the filter.

You can see that the large radii Photoshop sharpening filter enhances large details and adds additional contrast to the image (area contrast enhancement). The color spectrum of the image is already covered from the darkest to the lightest and there is already a decent amount of contrast too. This way you can add a presence to the image. You can also combine a couple of large sharpen passes but with smaller amount percentage so your image does not get distorted.

The radius and the amount of the effect depends on various factors. Try different settings and play with the image, so you can get a nice enhancement. Be careful not to kick out the details in the highlights and shadows.

This Photoshop sharpening trick can be specially useful when working with photographs of industrial equipment, such as showing some products, metal parts, cars, etc. You can totally out-contrast and sharpen them with no distortion visible. As the glass in the example.

Using this over-sharpening filter on a photo of a human might just be too much. On the other hand, using large radius filters to jazz up the depth and presence contrast, and after that using History brush to restore the distorted areas solves the problem. The good folks that created Photoshop thought of that too.

On semi-professional or amateur photos, you can use this filter to get rid of the low cost lenses “foggy” effects.

Slightly out of focus

This one is a classic. There are hundreds of Photoshop sharpening tutorials and explanations written about the subject, so I won’t get too much into this. It is simple. Due to the imperfections of the devices we use there is always a slight out of focus factor. To fix this use a small radii filter with grater strength. I recommend here the Photoshop’s Smart Sharpen filter again, that is specially designed for this. From options you can choose the sharpen mode (lens, Gaussian), the radius (I recommend 0.5-2.5 pixels) and the strength of the filtering.

Usually, you can do 2 Photoshop sharpening passes. One with 0.5 pixels and one with 1.5 pixels. The good thing with the Smart Sharpen is that it makes much more “auras” than the classical sharpen (unsharp mask) filter. If the original image is already sharp, it’s enough to do a single sharpening pass to get the details more enhanced.

Original casual photo

Casual photo sharpened to the maximum

On this image (on the right) I applied a Photoshop’s smart sharpen two times. First with parameters amount:35%, radius:1.6 pixels, remove lens blur, more accurate on and next with amount:15%, radius:0.8 pixels, remove lens blur, more accurate on.

Only be careful not to use too much strength. If you over sharpen the image it will look like it’s frozen and distorted. Have style!

Motion blur

In general, if you are working with a professional photographer (or if you are one) you will almost never have to deal with this. But if you took a nice photo on your vacation from a fast moving car, and you really like it, but it has some motion blur involved, you will need to use the Smart Sharpen filter.

Using the Smart Sharpen filter set the Remove option to Motion Blur, set the direction of motion, radius to the approximate length of the motion, and depending on the amount of motion the Amount factor.

A tip I’ll share with you here. Rather than guessing the angle of the motion you can measure it using the Measure Tool (keyboard shortcut I, same group as the Eyedropper tool). Afterward just write in the motion’s angle to the Smart Sharpen dialog window.

Sharpening the living s…t out of your images using Photoshop or Gimp

Most Photoshop users are content with very little sharpening, but so much more can be done. I see a lot of users usually hitting some “standard” Photoshop sharpening to the image and consider it finished. Which, in some general sense, is OK. But, if you want to become a professional, I warmly recommend using the tricks explained in this tutorial.

Note that instead of Photoshop sharpening you can use Gimp’s sharpening tool. The drill is the same, parameters might be different.

For the conclusion I took the liberty of taking images and passing it through a series of sharpening filters. Remember, I only used the sharpen filter. Ready? Let’s rock!

Here is what I did using Smart Sharpen with Remove: Lens Blur and More Accurate turned on in Adobe Photoshop.