Remove Focus Blur

In focus.

Some images are degraded by poor focus. The Remove Focus Blur tool can help to restore these images. This tool can be especially handy to retrieve information from an out-of-focus image. For example, it can make text readable that otherwise would be too blurry.

The Deconvolution tab.

Deconvolution

Deconvolution method You can select between Faster and Higher quality. The Faster option is usually sufficient in most cases.

Deconvolution sharpness This option tries to restore details lost by the noise and artefact suppression. This should usually be set to High.

Deconvolution noise and artefact suppression This option sets how much noise and artefact suppression will be applied. Usually, setting this to High is a good idea, but if you have a very clean, noise-free image with a sharp blur kernel, you can set this to Low or Medium.

Deconvolution smoothing If a photo has a lot of noise or artefacts, smoothing can be used to make the image look more appealing. Lower values produce less smoothing. This should be set as low as possible. Please note that this option can only be used with the Faster deconvolution method.

Convert to linear pixel values Some file formats (like JPEG) apply a gamma curve to a photo. This can be undesirable when doing deconvolution as it can reduce the effectiveness of the deconvolution and blur kernel detection algorithms. When this setting is checked, the image is converted back to linear pixel values by undoing the effect of the gamma curve.

The Blur Kernel tab.

Blur Kernel

Blur kernel type Usually, this should be set to Out of Focus, as this is the best shape for removing focus blur. But other shapes, especially Cauchy and Lorentzian, can be useful too, especially when there is a combination of factors that led to the image being blurred (such as being out-of-focus plus atmospheric turbulence).

Blur kernel size This sets the overall size of the blur kernel. A larger value produces a larger blur kernel. The size directly corresponds to the degree of defocus – a smaller value should be used for slight blur, and a larger value should be used for a very out of focus image.