Rich Ditch's Photography Blog

May 4, 2012

Mourning Dove Moire

Filed under: Birds, curiosities, digital benefits, surprise results — richditch @ 7:29 pm
Mourning Dove

Mourning Dove

Nikon D70, Nikkor 300/2.8 AF-S lens with TC20E (2x), ISO 200, 1/640th second at f/9, -1/3rd stop ev, tripod

I recently decided to rework a Mourning Dove image from 2005, taken with my first digital camera about 6 months after I started using it. I’ve liked this since I shot it and plan to use it in a “weekly challenge” web site with a monochrome theme.

I like the unusual perch (a bit of granite beside a lake in Tucson, AZ), I like the open beak, and I like the “understated” colors.

What I don’t like about the image (although I find it fascinating) is the small area of red and green that shows up on the wings. Here is the area as a 1:1 crop from the image viewed at 100% in photoshop.

Moire example

Moire example

I think is is the phenomenon known as moire – an interference pattern created from two overlapping patterns with very close spacial frequency. In this case it is the horizontal and vertical fine detail of the feather that is almost the same spacial frequency as the photosites on the sensor in the Nikon D70. This is one of the technical issues of digital capture, and camera manufacturers deal with it by overlaying an anti aliasing filter on the sensor. A strong filter will keep moire patterns from occurring, but at a tradeoff in image sharpness. Camera designers juggle this tradeoff with varying outcomes.

Nikon has just released the impressive Nikon D800, along with the D800e that excludes an anti aliasing filter for maximum sharpness. It remains to be seen how much of a problem moire will be in real world imaging. It might be that Nikon has provided a way to deal with this in their raw conversion application Nikon Capture, but I’ve not seen anything about it at ther review websites yet.

Note that this is the only time I’ve seen this effect in thousands of nature images I’ve shot on digital with the D70, D200, and D300.


1 Comment »

  1. Great to visit your blog.Great photography.

    Comment by rupam — May 5, 2012 @ 7:33 pm

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