Chromatic Aberration |
More about this plot can be found in the page on Chromatic Aberration. Much of this plot is grayed out if the ROI is too close to the center for reliable CA measurements (less than 30% of the distance to the corner). | |
Red, Green,
and Blue
lines (bold) | Edge profiles for the R, G, and B channels (original, uncorrected). (Standardized sharpening is not used for chromatic aberration.) |
Black line (dashed) | Edge profile for the luminance (Y) channel. |
Dashed
magenta line (bold) | The difference between the highest and lowest channel levels. (All channels are normalized to go from 0 to 1.) The visible chromatic aberration is proportional to the area under this curve. |
Left column
text | Input settings: Plot title, profile orientation (Horizontal profile corresponds to a vertical edge, etc.), image dimensions (WxH), total megapixels, gamma, ROI size, ROI location. |
Right column
text (results) | 10-90% rise distance (original; uncorrected) in pixels and rises per picture height (PH). | CA (area): Chromatic aberration area in pixels. An indicator of the perceptual severity of CA. The area between the channels with the highest and lowest levels. In units of pixels because the x-axis is in pixels and the y-axis is normalized to 1.Affected by both lens and demosaicing. Explained in the page on Chromatic aberration. | CA (area) %: Chromatic aberration area as a percentage of center-to-ROI distance. A better indicator than pixels (above). Equal to 100 * (CA area in pixels) / (distance from center of image to center of ROI in pixels), corrected for the edge angle. Relatively independent of the ROI location because CA tends to be proportional to the distance from the image center. It is also independent of the number of pixels in the sensor. Explained in the page on Chromatic aberration. Approximate meaning: Under 0.04; insignificant. 0.04-0.08: minor; 0.08-0.15: moderate; over 0.15: serious. | CA (crossing): Chromatic aberration based on the edge centers (where the edges cross 0.5). This is generally smaller than CA (equiv.) and less indicative of the visibility of the CA, but more indicative of lens performance. This measurement can be very different from CA (area) due to the effects of demosaicing. It is primarily the result of lens chromatic aberration, and tends to be very close to CA (area) when Bayer RAW images are analyzed. | R-G, B-G :Red-Blue and Red-Green spacings in percentage of center-to-corner distance. Useful for correcting CA, especially when applied prior to demosaicing. Displayed only in Imatest Master. | Average pixel levels in the dark and light areas. Clipping can occur if they are too close to 0 or 255. |
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