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Message: <blockquote data-quote="ericbowles" data-source="post: 2462114" data-attributes="member: 103292">The D7000 will actually focus at f/8 but it requires good light.  Nikon is conservative and the reported limits are for reliable AF.One clarification - the reported focus is usually for a lens wide open regardless of what aperture is selected.  Most cameras will provide a wide open view through the viewfinder and you use the DOF preview button to see how it really looks.  So a 2x converter on an f/4 lens is f/8 wide open - which is borderline on the D7000.  Even if you chose f/11 for your aperture setting, the combination is f/8 wide open and should focus with good light and a good subject.  My experience is when it comes to AF the center sensor is better than the surrounding sensors - and much better than the outer sensors.  Darrel Young has documented that for the D800 and I expect it is the same for the D7000.The Nikon 300 f/4 provides better image quality than the Sigma 150-500 even with teleconverters.  The bare lens is clearly better, and nearly as good with the 1.4 teleconverter.  With the 1.7 lens you have an effective 510mm - borderline on the Nikon but at the point where the Sigma zoom is losing quality as well so the Nikon is still as good or better (in my opinion <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" /> ).</blockquote>

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