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The concept of sharpness

Photo by ROMBO from Pexels

You see them again and again, totally over-sharpened images. Funny Jesus halos were created, hair looks super dry, and somehow everything becomes cheap again.

What is sharpness?

Sharpness is in contrast. The contrast in the form of differences in brightness at edges and details – but also color contrast or saturation contrast. Yes – even the image content can affect image sharpness.

Adobe Photoshop looks for edges when sharpening them and makes them lighter on one side and darker on the other. Photoshop has no idea of color contrasts.
Photoshop can only make luminance contrasts:

Let’s take a closer look and do the same thing again:

Pay attention to the eye – that’s nice and sharp in this image – unfortunately, the skin texture suffered from it, the hair is strawy, and the hands “glow”.

But for luminance processing, there is an excellent, manual tool: Dodge & Burn. So here the ” manually sharpened “version:

In this example, too, the eye is sharp – and there are no side effects. Incidentally, this took almost 2 minutes.

Sharpness through color contrasts

Let’s take a look at this image here:

The two colors are very similar – the red and the orange differ only by a small offset in color. Saturation and luminance are the same. If we now change one of those color fields in hue (but leave the saturation and luminance the same), this is the result:

The separation between the two fields is so strong that even JPG compression reaches its limits and shows artifacts in the middle. The contrast is extreme here – only by changing the color tone.

Transferred to an image, you could apply it as follows:

Here the color tone was changed only minimally, and a sharper image emerged. A very subtle effect – again without side effects.


If you want to have sharp images, you can keep the contrasts and contrast edges in mind when retouching – this usually makes subsequent sharpening obsolete. At Dodge & Burn, I always try to darken the edges a few percents more and lightly lighten the other side of the edge. When it comes to colors, I pay attention to the color harmonies, so that you automatically achieve very harmonious, but at the same time, sharp contrasts.

A little hint at the end

If you sharpen while using the raw converter (meaning before retouching) or pull the saturation upwards, you will get a sharper picture, but in the end, you do twice the work. All of the problems highlighted by this global sharpening also want to be eliminated again. It is better to use the raw conversion for a somewhat flatter but balanced image and to increase the sharpness in the image during retouching deliberately.

Stay tuned for the next blog article regarding sharpness in the upcoming week.

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