Sharpening and Noise Reduction in Photoshop

Photoshop: Sharpening and Noise Reduction

Photoshop includes several tools you can use to correct your images. In this lesson, we'll show you how to make the following corrections:

• Sharpening: If an image is less clear than you'd like it to be, you can sharpen it.
• Noise reduction: If an image has a lot of noise, or graininess, you can reduce the image noise.

We'll also cover the importance of using these tools correctly. If they are misused, sharpening and noise reduction can actually cause problems. If they are used with care, they're a great way to add polish to your images.

Example Images

If you'd like to follow along, you can download our example images below. Click any image to open the full-sized version, then right-click and select Save Image As.

1. Sharpening

Sometimes an image may not be as clear as you'd like it to be. Sharpening can help make it look crisp and clear by enhancing the edges of objects in the image. However, adding too much sharpness can lead to a loss in image detail.

As you can see above, the center image looks crisp, but the image on the right has been over-sharpened. This causes unnatural white borders, known as halos, and introduces image noise into the background.

Image Sharpening Level: 50%

The Unsharp Mask Filter

The unsharp mask is the primary filter used for sharpening. It gives you control over these three key settings:

• Amount: This determines how much sharpness will be applied. It varies based on your image size, so experiment freely.
• Radius: This controls the size of the details sharpened. We recommend a low value between 0.3 and 0.5 for most photos.
• Threshold: This tells Photoshop to ignore certain parts of the image (like noise in the sky). We recommend keeping this at 0 most of the time.

How to Apply an Unsharp Mask

1. Duplicate Layer: Right-click the layer and select Duplicate Layer. Name it "Sharpened". This protects your original.
2. A dialog box will appear. Type aname for the new layer, then click ok In theis example , we'll call it Sharpened..
3. Select Filter: Go to Filter > Sharpen > Unsharp Mask.
4. Adjust Settings: Choose your radius and move the Amount slider while watching the preview window.
5. Compare: Click and hold inside the preview window to toggle between "before" and "after". Click OK when finished.

2. Noise Reduction

Low light can cause images to look grainy. You can compensate for this by reducing the image noise, which smooths out these pixels for a cleaner look.

Key Settings to Know:

• Strength: The overall level of reduction. Start at maximum (10) to see the effect, then dial it back until it looks natural.
• Preserve Details: Determines how many lines and details are saved. Too low will cause "smearing"; too high cancels the noise reduction.
• Reduce Color Noise: Fixes those rainbow-colored speckles (chroma noise). We recommend keeping this value relatively low.
• Sharpen Details: Adds back a tiny bit of crispness lost during the smoothing process.

How to Apply Noise Reduction

1. Duplicate the layer and name it "Noise Reduction".
2. Go to Filter > Noise > Reduce Noise.
3. Adjust settings based on the preview. If your image starts to look like a painting, you've gone too far. Click OK once satisfied.

Hands-on Challenge!

1. Open the flower_fullsize.jpg file in Photoshop.
2. Duplicate the layer, and apply an unsharp mask until the petal edges are clear but natural.
3. Open the ferris_wheel_fullsize.jpg file.
4. Duplicate the layer and apply noise reduction to clean up the grainy night sky.
5. Save your work as a JPEG using File > Export > Save for Web (Legacy).