Sharpening and Noise Removal
BPIC - Sharpening and Noise Removal
There are several ways to sharpen an image in Photoshop, but to start with, you must correct the noise within the photo or you will end up sharpening the noise as well and making the image worse. Here is a great technique using Surface Blurs and Channels - the last thing you would expect in a sharpening tutorial.
Once the noise has been removed we show you how to master two of the sharpening filters: Smart Sharpen and Unsharp Mask.
The sharpen filters are found in the top toolbar under Filter>Sharpen. Avoid using the sharpen tool in the sidebar if possible – it’s okay for small areas such as eyes, but the other filters work so much better. In this filter menu you will find the Sharpen and Sharpen More options. These will apply a basic overall sharpening effect to your image. In this menu, you will also find the Sharpen Edges, Smart Sharpen and Unsharp Mask options.
Remember, before applying any filter effect, you will need to duplicate your background layer so you will always have an unedited version to fall back on if the effects don’t work out as planned.
Duplicate a backup
With the blurred photo you wish to repair open, duplicate the background layer. To do this, drag it over the Create New Layer icon at the base of the Layers Palette. Press
the eye icon next to the bottom layer to hide it for now.
Work on the newly duplicated layer in RGB format. Go to the Channels Palette; switching off the eye icons on each channel one at a time reveals which colour holds the most noise within your image.
Keep the worst channel visible only. Click on this channel to highlight it and go to Filter>Blur>Surface Blur. A dialog box will open. We are adding a Surface Blur to remove the noise, but keep the edges in the images sharp still.
In the dialog box, move the sliders so they are on the far left. Gradually increase them both, making sure the Preview box is checked so you can see the progress. We have used a value of five for both.
Repeat the process
Now work on the other two channels in the same way. These may not have held as much noise as the other channels so the Radius and Threshold values will not need to be as high, if the treatment is needed at all.
Now the noise has been banished, go back to the Layers palette. Duplicate the visible layer and hide the middle layer. Now we are ready to sharpen correctly. Go to Filter>Sharpen>Smart Sharpen.
Open the filter
Working on a newly duplicated layer so you have a backup, open up the Smart Sharpen filter. This filter gives you the most options when sharpening which can all be seen in the dialog box, but is tricky to master.
The Amount slider allows you to decide how light or dark Photoshop makes your pixels. The best range is between 50-150%, anymore and you will see your image halo slightly. Use this slider in conjunction with the Radius slider: moving one will affect the other.
Keep the radius small, under 5%, as the size of halo created with the Amount slider will increase too much. Move both sliders minimally, keeping an eye on the Preview window for changes. Work through all of these steps first to get the best results.
Use either the Gaussian or Lens Blur options from the drop-down menu, whichever makes the best improvement. The Angle mode will only appear if working with the Motion Blur - use this to correct the angle within your image.
Checking the More Accurate option will slow your computer down. It does add more precision to your image, but in most cases it’s unnecessary. Clicking onto the Advanced tab lets you control shadow and highlight amounts in your image.
Moving the Fade slider controls the amount of sharpening applied to lights and darks, allowing the sharpening to only affect certain areas. Tonal Width adds more sharpening to shadows or highlights, depending on the tab you’re working under.
Don’t expect miracles
Don’t oversharpen – it will never be as sharp as a brilliant-quality photo but we can improve images, saving many. Make small adjustments, and if you can’t get to grips with this tool, try the Unsharp Mask that’s explained next.
Open the filter
This is the most commonly used sharpening tool (Filter>Sharpen>Unsharp Mask). It is easier to use than Smart Sharpen and is a quick fix every time. It is set to remove Gaussian Blurs, the most common problem in unsharp images.
The Amount and Radius sliders work the same as in the Smart Sharpen filter (see previous step-by-step). There’s also a Threshold slider which determines what pixels are classed as an edge. Moving this controls the level of sharpening.
Keep this setting above three levels, so that the image doesn’t become too harsh. Keeping it at zero means every pixel is as sharp as can be. Start on the Radius slider to determine how sharp you want things. Too high and it will look bad, like our example.
Keep unchecking the preview box to see how the sharpening is affecting the image. This filter is much quicker than the Smart Sharpen filter, so it shouldn’t keep you waiting long. The final values were: Amount: 100%, Radius: 1.0 pixels and Threshold: 3 levels.
Print to check
The pixels on screen are much bigger than a printed out version, so keep this in mind when working and remember to print out a copy before closing down. Don’t over sharpen, or you will bring more flaws to the surface than originally thought. Remember also, that more sharpening is applied to matte paper than to gloss paper due to the key in the paper which means it’s harder for the colour to spread across it.
The Sharpen, Sharpen More and Sharpen Edges filters do not let you edit values like the other two options in the menu. Sharpen and Sharpen More are okay for minor problems, but are best avoided. The Sharpen Edges filter, can be useful when sharpening is needed on a face. Using this filter on skin means the pixels do not blur so much at edges.