Fritillary butterflies on thistle, July 2009, taken with Nikon D90

As is my habit, I buy and sell photography gear somewhat regularly.  Some equipment I have had for a very long time because of its quality and/or irreplaceable function.  Others I buy and use for a while and then sell off in quick succession.  Such was Nikon's D90 camera.

The lens I used for this photo was Nikon's 80-400 telephoto zoom, not the "S" version that I currently own.  The combination of camera and lens was good, but looking back I find that the images are somewhat soft and lack the quality that I currently expect from my equipment.

One of the problems with low-megapixel cameras was that they used something called an anti alias low pass filter just in front of the sensor.  Its purpose, somewhat ironically, was to produce a tiny amount of blur on the sensor to reduce the effects of moire.  You rarely get this problem in nature, but the human world relies so heavily on repeated patterns that moire often shows its head.  What is moire?

Moire is a wave-interference pattern that happens when a sensor's repetitive cell design clashes with the repetitive design on fine details, usually related to fabrics.  You can see in the example below how the fabric weave has artificial ripples in it that are a result of the clash between the the two patterns (sensor vs image).  In real life there is no such clash.  You can see an example below.

Moire interference pattern from a fine-weave shirt.

Modern cameras don't have this problem as the high resolution allows image capture without moire.

I owned the D90 for only a little while then sold it off for my next, and one of my favourite camera bodies, the D300.

Thanks for reading.

Eric Svendsen     www.ericspix.com



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