Pentax K-5 II / IIs Review

Moire

The lack of an anti-aliasing filter increases the risk of false color and aliasing patterns (moiré) in images with very fine detail. For a long time (see later samples), we were not successful in provoking moiré when taking photos of landscapes with the Pentax K-5 IIs, but after photographing a textile with a very fine repeating pattern, we quickly saw moiré, though only when enlarged to full size.

Here is a original shot; as you can see, the moiré is not discernible at this size:

Pentax K-5 IIs shot with invisible moire

This is a 100% crop of the above photo, with the most significant moiré patterns circled:

Pentax K-5 IIs Moire

The degree and presence of moiré depends highly on the direction of the lines in the texture compared to the position of the sensor, as well as how far away the pattern is.  Click the photo above to enlarge.

It is not always a question of moiré or no moiré, though. In the case of the Pentax K-5/II vs. the K-5 IIs, it is a question of how much. While we were initially unsuccessful in provoking moiré outdoors, our test chart on the other hand was more cooperative and brought out mild moiré in K-5 images and more pronounced moiré in K-5 IIs images. Regarding contrast and resolution the K-5 IIs again came out ahead of the K-5.  Don't get us wrong, though- the moiré visible on the normal K-5 / K-5 II is negligible and will virtually never be seen in practice.  The risk is higher with the K-5 IIs, but still small enough to have little practical significance for most applications.

For this test we used an smc Pentax DA 35mm F2.8 Limited Macro lens. The distance to the target was 3.5 m (100x the focal length) and the light was daylight coming through the windows - no artificial light.

The scene:

The moire scene

K-5 IIs: The Effect of Sharpening

For the first set of images we varied the sharpening in post processing from no sharpening over unsharp mask 50%, radius 1 threshold 0 to unsharp mask 100% radius 1 threshold 0. We used RAW images in DNG format processed with Adobe Camera Raw (ACR) and Photoshop CS6. Our conclusion is that sharpening has no significant effect on the moiré but it enhances the overall image quality as expected.

Pentax K-5 IIs

ISO 100 F4

No sharpening

ISO 100 F4 no sharpening

ISO 100 F4

usm 50% r1 t0

K-5 IIs ISO 100 F4 USM 50 1 0

ISO 100 F4

usm 100% r1 t0

K-5 IIs ISO 100 F4 USM 100 1 0

 

Comparing K-5 and K-5 IIs from ISO 100 to 12,800

Both cameras can produce moiré, the K-5 IIs much more so than the K-5, but the K-5 IIs also provides increased resolution. The images are based on RAW files with no postprocessing other than conversion to JPG in Adobe Camera RAW and "100%" cropping in Photoshop. No sharpening was applied. High ISO noise reduction was turned off in the cameras. Even at F11 where diffraction has set in we get moiré with the K-5 IIs when used with a high quality optics. The K-5 produces no moiré at F11.

Pentax K-5 IIs
Pentax K-5
ISO 100 F4
ISO 100 F11
ISO 200 F4
 ISO 200 F11
 ISO 400 F4
 ISO 400 F11
 ISO 800 F4
 ISO 800 F11
 ISO 1600 F4
 ISO 1600 F11
 ISO 3200 F4
 ISO 3200 F11
 ISO 6400 F4
 ISO 6400 F11
 ISO 12800 F4
 ISO 12800 F11

The advantage in image quality of the K-5 IIs decreses as ISO increases, and is less pronounced at F11 where lens diffraction starts taking its toll on resolution.

Moiré with Distance

The below photo shows the test chart shot from a distance of 3.5 m and 4.5 m, respectively. The moiré pattern basically has the same size and look. With a target as this star chart the color pattern doesn't diminish with distance.

 distance


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