Some images crops ,moire and aliasing

The test was to show moiré patterns from a modified Siemens star target. The target has 90 black spokes equivalent to 90 cycles around any diameter of circle centered on the black square. The target has circular marks at 30px intervals radially outwards from the middle.

90 cycles is sufficient for older sensors with large pixels e.g. SD10 9.12 um, SD14 7.8um, but Bart van der Wolf has designed one that, 144 spokes, is more suited to Merrill sensors - see here.

The viewing distance was about 45" or 113 cm. An 18-50mm kit lens was used and the SD10 set to LO resolution, giving it an effective pixel pitch of 18.24mm. Selecting the larger pitch allows moiré to occur at a closer viewing distance.

Four shots were taken at a lens setting of 18, 28, 35 and 50mm. These settings varied the framing of the target so as to find the best shot for moiré patterning. This turned out to be the 28mm shot at top right, sin duda.

It is better to view the image at the original size.

A "bonus" occurred in the 18mm shot at top left. The center area of the target was found to be blurred out in the image - perhaps due to lens performance. However the blurring commences at 6.5 lp/mm; a remarkably low value.

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Regards,
Ted http://tcktek.blogspot.com
SD10/70mm macro