Focus peaking
The focus peaking (from English focus , image sharpness and English peaking , exaggerated ) is a method for the excessively emphasized display of sharply depicted contours in photographic images, which is used especially in digital photography for manual distance adjustment of subjects.
functionality
By analyzing the contrast between neighboring pixels in digital images, local information on image sharpness can be obtained across the entire image , regardless of the object distance , focal length and aperture . This can be displayed on a screen or in an electronic viewfinder using contours that are highlighted in color or in terms of brightness .
For edge detection in digital images, two-dimensional, digital filters, such as two-dimensional Laplace filters , can be used, with which the modulation can be efficiently approximated. With these filters, the image data are usually mathematically convoluted using a suitable mask .
- Focus peaking
Photograph of a sharply depicted tree branch in an out of focus alley
Edges in the image after filtering with a high pass
Tone value increase and red coloring of the filtered edges in the image
Overlay of the photograph with the determined edges
Areas of application
The sharpness actually set can be determined quickly and reliably using the edges highlighted by the focus peaking. When manually setting the object distance on a camera lens, the user can immediately see all object planes with the sharp contours in the entire image.
This is useful with large apertures , as the depth of field can be very limited and the focused object plane may not be recognized with sufficient accuracy with autofocus systems or on focusing screens in viewfinders of SLR cameras and in non-magnified viewfinder images. In the case of small apertures, the focus peakings can be used to quickly determine the size of the depth of field between the near and far point.
Modern digital cameras with a live view function can display the focus peaking in real time before recording . The first camera models with focus peaking include the Leica M , the Olympus OM-D E-M1 , the Pentax K-01 and Sony 's A7 series and SLT cameras such as the Sony Alpha 77 . The function is also available in video mode with some cameras, so that manual focus tracking is made much easier during the recording.
Focus peaking can also be used to subsequently determine the sharply depicted object plane in digital images.