left focus syndrome , cured yet?

Started Jun 3, 2013 | Discussions thread
Per Baekgaard Senior Member • Posts: 1,269
Re: left focus syndrome , cured yet?

_sem_ wrote:

Per Baekgaard wrote:

TITCHY wrote:

my only niggle now is why black does not "look" black on the lcd monitor .  purple/blueish   when enlarged anything above 50% or so .  other than that ,i concede my initial suspicions were user error ,obviousely I need to allow a fair bit of time adapting to the way the D800 works and behaves .

This is not your camera's fault but very likely due to (Longitudinal) Chromatic AberrationĀ in your lens; a "known deficiency" with many fast lenses. If you stop down to f/2.8 you'll be good for most purposes -- and in many cases you'll be just fine with that lens also wider than f/2.8

Yes, but... there should be no tint with sharp focus... loCA purple/green tint appears outside the plane of sharp focus

Well, yes, kind of, but...

As far as I have understood, when you have LoCA, the sharpest focus plane is not the same for the longer waved red, the green and the shorter waved blue light (http://en.wikipedia.org/wiki/Chromatic_aberration).

So a white blop of light (for simplicity: "equal" parts red, green and blue) might be in focus for the green parts of its light spectrum, but slightly out of focus for the red and blue parts. The red and blue parts will together thus appear slightly fuzzy/diffuse and spread their light around the edges. This will make up some kind of magenta/purple tint, typically mostly visible on the black parts that surround the light parts.

I have several (at least 3) 50mm Nikkor lenses here, and they all exhibit this to some extent.

Not all "purple fringing" is caused by LoCA; flare could also be part of the cause.

But then, I could be totally wrong on this and some other phenomena might be more prominent

- Per.

 Per Baekgaard's gear list:Per Baekgaard's gear list
Nikon D800 Nikon D500 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S Nikkor 14-24mm f/2.8G ED Nikon AF-S Nikkor 24-70mm f/2.8G ED +17 more
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