Started Mar 24, 2013 | Discussions thread
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Michael Harvey Contributing Member • Posts: 636

With the new Nikkor 80-400mm and D800, I'm seeing fewer "keepers" when shooting at long distance (skittish wildlife, air shows). Closer up - no problems...great IQ.

Some have suggested that the glass itself is to blame, despite the test reports showing the lens to be of high quality. Let me suggest another (more likely, I think) theory.

I have been a life-long amateur astronomer and, as such, I'm very aware of "poor seeing conditions". This refers to the distortions caused by turbulence in the atmosphere between the observer and the object being observed. There can be "local" seeing, like heat waves rising off a nearby driveway or rooftop that the observer's telescope is looking over, or even "fast" seeing caused by high altitude winds (i.e. the jetstream).

The first example is like what you see when looking down a hot roadway...wavy, shimmering, indistinct images. The second is usually more of a 'smeary' effect, like rain sheeting down a window. There are other types of "seeing conditions"...I'm just giving a couple of examples.

Here's the thing: the severity of the effects of "poor seeing conditions" are directly related to the aperture of the telescope being used. Smaller scopes are less affected. Some observers won't even use a LARGE scope on nights of "poor seeing". And the aperture of the scope determines the resolution of the scope! The larger the aperture - the higher the resolution. Smaller scopes (with lower resolution) are less affected because they can't resolve as many turbulent cells in the air (some are large, some are small).

Apply the same comparison to our cameras. The D800 has 36mp resolution.                              It can resolve atmospheric distortions that are invisible (or certainly less obvious) to a camera with LESS resolution!

Astronomers have "aperture masks" to reduce resolution on bad nights. These are simply cardboard discs that fit over the end of a telescope and have a hole cut in them that is smaller than the scope's full aperture. WE have smaller sensors and cropping settings that can perform the same function.

We already know that increased resolution cameras will show formerly unnoticed shortcomings in lens quality. NOW we know something else!


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Mike Harvey

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