AZImage help - Detailed help - IP forms - Grayscale
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Some images (like portrets or detail images) look better in gray tones. Grayscale photos were common with traditional cameras due to the use of black-and-white film, but are occuring in the digital photography only as a product of a later processing step. Conversion of a color image to grayscale is not unique; different weighting of the color channels effectively represent the effect of shooting black-and-white film with different-colored photographic filters on the cameras. A common strategy is to match the luminance of the grayscale image to the luminance of the color image - see below.
This tab allows to set the parameters for a conversion to grayscale. AZImage supports a variety of grayscale algorithms, they are shown below together with the corresponding conversion results.
- luminance. Adds together 30% of the red value, 59% of the green value, and 11% of the blue value to obtain the grayscale value. This is the most encountered method.
- average. The grayscale value is the average value of the three components.
- min/max. Works by selecting the minimum or the maximum of the three R,G,B values when producting the output gray. It is good algorithm when trying to improve the contrast or to reduce the noise in the photograph.
- sRGB. Adds together 21% of the red value, 71% of the green value, and 8% of the blue. Similar to some grayscale monitors.
- channel. Works as a color filter that produces a graylevel image by setting the values from a single RGB channel (selectable in the second combobox) as grayscale values.
The results are offen significantely different (see below) and there is no method that fit all usecases.
Few Tips:
Use the two preview images to compare different grayscale algorithms, since the result dependens a lot on the source image.
You can use one of the RGB channels to fade out a uniform background - for example a green one in the sample image.
You can use min/max to decrease/increase the contrast between the main subject and the background, provided that the main subject contrasts with the background in the picture.
See Also
Image processing main form.
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