[Brightcolours]

[quote name='Klaus' timestamp='1314376114' post='11058']

Here's a CA spot that I measured at 12mm f/4 - border region:









I don't know how Imatests calculates the CAs but 0.6px doesn't seem to be far off in this sample. It's difficult to tell visually from the tilted quadrant because the CAs will actually pollute the aliasing thus emphasizing the effect somewhat

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Thanks for the sample, to get a bit more insight into the measuring process. Of course, since pixels always are whole and never half or 1/3rd, CA almost always appears in more pixel real estate than it should. This makes measuring difficult, and also gives a dilemma what actually to measure (CA width in the captured pixelated image, or CA width in the projected image.



There is a disconnect in measuring the CA in "pixels" and coming with 0.6 to 1.5 pixel values, and looking at the image and visually seeing the CA being spread over 5 to 6 pixels wide, though. In this case, CA probably gets exaggerated by the distortion correction too.