Flattening an image decreases the quality

Sharpening Photos and Removing Noise: Techniques and Tips

It never ceases to amaze: With the right amount of sharpening, even mediocre pictures often look much better. Even clearly blurred images can be enhanced with it. That is why we will show you the most important sharpening techniques: all controls and processes including zooming and layering techniques.

When using it, however, make sure that you do not add to the noise when you sharpen the image. Rather, you should smooth out the unsightly grains that arise especially at high ISO sensitivities in advance. You will also find the best tips for this here.

The right zoom level

When focusing and removing noise, you edit the fine structure of your image file. You can recognize important changes particularly precisely in the 100 percent zoom level. It can also be called "1: 1" or "Actual Pixels". One pixel of the photo appears exactly on one pixel of the monitor - it is no longer more precise.

There are special buttons and keyboard commands in the programs for this important zoom level. Check the quality on a section that shows both smooth surfaces and distinctive contours. In particular, examine shadow areas for interference. But: If you present the recording in a zoomable way on the Internet or print it, the pixels will be converted. The 100 percent zoom level may show your photo unrealistically clearly. You should therefore also check the image on a 50 percent scale (1: 2) before printing. If you want the photo to be zoomable on the monitor, you can also test odd zoom levels such as 23.45 percent. Because what appears error-free in the 100 percent representation can appear distorted in a "crooked" reduction.

You can even view an image at two different zoom levels at the same time: To do this, open the "Window / Arrange" submenu in the Photoshop full versions. First select "New window for" and then "2 side by side". In Photoshop Elements these functions are in the submenu "Window / Pictures".

Reading tip:Photoshop - 50 Tips and Tricks

Tip: The quick way to zoom level 100 percent: In Photoshop or Photoshop Elements, double-click on the magnifying glass in the toolbar. Or use the key combination [Ctrl] + [1], on the Mac [Command] + [1].

Strength, Radius, and Threshold

Many image programs offer several sharpening dialogs. Different settings are suitable depending on the image quality. The principle is always the same: differences in brightness in contrasting edges are increased - this increases the impression of sharpness. Familiarize yourself with these controls:

  • Strength or Amount: increases the intensity of the sharpener in general.
  • Radius: decides how wide the sharpening extends around a contour. High values ​​create ghost contours and halos. However, test the large "radius" on clearly blurred images. This may help with architecture and product photos, but less so with nature and portraits.
  • Threshold: determines whether the sharpening starts with large or even small contrast differences. If you raise the threshold significantly, the program will no longer focus on smaller differences in brightness. In this way you prevent the sharpening from increasing unwanted image noise, skin disturbances or JPEG image errors. So raise the threshold if the photo still seems too noisy.

Tip: A sharpening command that is used is called up in Photoshop programs with the key combination [Ctrl] + [Alt] + [F] or [Command] + [Alt] + [F]. If you want the function to run again immediately without seeing the dialog box, press [Ctrl] + [F] or [Command] + [F].

Selective sharpener

The most effective focus in the Photoshop main program is the "selective sharpener". In Photoshop Elements this function is called "Adjust Sharpness". From the "Reduce" or "Remove" drop-down menu, select, depending on the program version, the "Lens blur" or the inappropriately named defaults "Reduce depth of field" or "Shake".

The image noise is often only visible in the shadows. So, depending on the shot, you should focus the shadows less strongly than other brightnesses so that the focus does not cheer the image noise even further. The "Selective Sharpener" has a good function for this:

  1. First open the menu item "Shadows / Highlights".
  2. For example, under "Shadows", raise "Fade" to 50 percent. The higher the value selected, the less sharpened you will sharpen low tones. If you set the value to 0, correct low tones as normal.
  3. If you set the "tone width" to a value as low as 20 percent, the function only saves extremely dark shadow areas from focusing. On the other hand, if you increase the tone width to 80 percent, you also protect medium-dark areas of the image against changes. Experiment with the "Radius" value!

Tip: Only in Photoshop CC does the "Selective Sharpener" have a powerful additional function: the "Reduce Noise" slider. The higher you increase the value, the more completely uniform areas are left out of the sharpening. This works in a similar way to the "Masking" slider in the Raw dialog. You can use it to protect areas of skin or smooth walls against sharpening disturbances without first masking the affected areas.

Sharpening with RAW functions

You can also find high-quality sharpening in Lightroom and in the raw dialog of all Photoshop variants. It is basically lossless. Pay attention to these special features:

  • Amount: High "Detail" values ​​produce more grain, but also show more subtleties and are suitable for recordings with detailed structures. Low "Detail" values ​​make the picture smoother, but sometimes more artificial.
  • Masking: If the "Masking" value is 0, Photoshop sharpens the entire image area. The further to the right the slider is, the more low-contrast areas of the subject are protected against sharpening - for example areas of skin, sky or smooth walls. This is reminiscent of the "Reduce Noise" slider in the "Selective Sharpener": Weaker image disturbances are not pointlessly emphasized by the sharpening.
  • Clarity: Directly below the general contrast corrections, this slider increases the mid-tone contrast and thus makes the image crisper.

Lightroom and the Photoshop full versions also offer output sharpening: It is applied to images that you transfer from the raw dialog to the main program, export as JPG or print. The process is intended to compensate for the loss of sharpness caused by printers such as color ink emitters.

In Photoshop's Raw dialog, click on the blue line below with technical data such as "Adobe RGB (1998); 16 bit; 5184x3456". In "Workflow Options" you then define a paper type and a thickness. In Lightroom you will find the output sharpening in the "Export" dialog as well as in the "Print" module.

Smart filter technology

Regardless of whether you are sharpening or editing the image noise - use the smart filter technology in Photoshop full versions from CS3 (2007): The change remains flexible and can be restricted to individual image zones. Here we just sharpen our eyes:

  1. Select "Filters / Convert for Smart Filters" or similar. In the next dialog click on "OK".
  2. Now follows "Filter / Sharpening filter / Selective sharpening". Set the controls so that the eyes come out easily - even if other parts of the image appear exaggerated.
  3. After clicking "OK", the "Selective Sharpener" appears with its own layer mask in the layer control panel. The mask is initially white: the sharpener affects the entire image. Click the white thumbnail in the Layers panel and press [Ctrl] + [I] or [Command] + [I]. This turns the mask black and the focus is completely suppressed.
  4. Switch on the brush with white foreground color in the toolbar. Paint over the eyes - only they will now appear sharply defined. In addition to the restriction to selected image areas, the smart filter has even more advantages:
  • With a click on "Selective Sharpener" you can change the controller values ​​at any time in the layer control panel - for example after a test print. The eye symbol completely hides the effect.
  • To the right of "Selective sharpener" click on the small slider symbol for the "Fill options": If the effect becomes too strong, you can reduce the "Opacity".
  • The original is retained without loss. If you want to forego sharpening, drag the smart filter into the trash can in the Layers panel.

Tip: If you double-click on the black and white mask thumbnail, change the "Density" and "Soft edge" parameters of the filter mask in the "Properties" panel.

Denoise

In Photoshop and PSE, "Filter / Noise Filter / Reduce Noise" helps against image noise. The "Strength" slider controls the intensity. Other important functions in this dialog:

  • Preserve details: Choose how much fine structures are preserved. This mainly affects the brightness noise. High values ​​like 80 preserve details, but the function has a weaker effect.
  • Reduce color noise: combats pixels with color outliers. High values ​​distort the picture with desaturated areas and ghost shadows!
  • Sharpen details: increases the sharpness in full PS versions. However, high values ​​produce new disturbances.

Noise is often particularly strong in one primary color, often in blue. In the Photoshop full versions you can therefore edit the basic colors individually. Click on "Advanced" then "Per Channel". Example: In order to reduce noise and smooth the blue channel more, take the moderate "Strength" of 3 in the "Overall" area and raise the "Strength in the" Blue "channel to 8 or 10.

In Lightroom and in the Photoshop Raw dialog, you can denoise brightness and color in the "Details" area separately and without loss. Start with color noise. The particularities:

  • Contrast in the "Luminance" area, ie against brightness noise: High values ​​protect the image contrast, but can cause spots. Low values ​​create a less contrasting overall picture.
  • Smoothing in the "Color" area, ie against color noise, limits colored color noise and minimizes color differences. However, values ​​that are too high desaturate the affected image area.

Tip: Correcting individual basic colors in the "Reduce Noise" dialog is cumbersome. Better to click a single base color in the Channels panel, such as "Blue", and then click the eye icon next to "RGB". You will see the picture again with all the basic colors, but "blue" is being processed. Only now do you call up "Reduce Noise".