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<blockquote data-quote="WayneF" data-source="post: 533960" data-attributes="member: 12496">You are not understanding how it works.&nbsp; The camera keeps the lens wide open at all times, for the viewfinder and for focusing, which is aided by the brighter light wide open.&nbsp;&nbsp; You are NOT focusing at f/22, you are focusing with the 28-85mm lens wide open, at f/3.5-4.5.To better understand, try this.&nbsp; Setup the camera for a f/22 shot, as before. Then while watching through the viewfinder, reach up and press the Depth of Field Preview button, top button at the side of lens, under the shutter button.&nbsp; You will then see the difference in viewing with the lens wide open, and viewing when stopped down to f/22.&nbsp; You can also simply look into the lens as you press the shutter button, and see it stop down to f/22 only for the shutter duration.For the TC, shooting at f/22 is no problem at all. The lens is wide open for focusing.&nbsp; The wide open aperture being more than f/8 is the problem.The 24-85mm lens is f/3.5-4.5 wide open.&nbsp; Even if this lens were compatible with TC (it's not), then the TC 1.7 would add 1.5 stops, so that even f/4.5 becomes slightly less than f/8, and still in spec. &nbsp;But the 200-500 lens is f/5.6, and adding 1.5 stops for 1.7 TC becomes 1/2 stop past f/8, out of spec.&nbsp; So Nikon advises forget it.&nbsp;&nbsp; It could still work sometimes, but difficult AF cases likely fail to focus. You would likely lose some shots. Nikon is advising against this try.ALL LENSES with a maximum aperture of f/4.8 or more are said to be incompatible with the f/8 limits of AF focusing with the TC-1.7. &nbsp;For the TC-1.7, this is f/3.3 for camera bodies that can AF at only f/5.6</blockquote>

[QUOTE="WayneF, post: 533960, member: 12496"] You are not understanding how it works. The camera keeps the lens wide open at all times, for the viewfinder and for focusing, which is aided by the brighter light wide open. You are NOT focusing at f/22, you are focusing with the 28-85mm lens wide open, at f/3.5-4.5. To better understand, try this. Setup the camera for a f/22 shot, as before. Then while watching through the viewfinder, reach up and press the Depth of Field Preview button, top button at the side of lens, under the shutter button. You will then see the difference in viewing with the lens wide open, and viewing when stopped down to f/22. You can also simply look into the lens as you press the shutter button, and see it stop down to f/22 only for the shutter duration. For the TC, shooting at f/22 is no problem at all. The lens is wide open for focusing. The wide open aperture being more than f/8 is the problem. The 24-85mm lens is f/3.5-4.5 wide open. Even if this lens were compatible with TC (it's not), then the TC 1.7 would add 1.5 stops, so that even f/4.5 becomes slightly less than f/8, and still in spec. But the 200-500 lens is f/5.6, and adding 1.5 stops for 1.7 TC becomes 1/2 stop past f/8, out of spec. So Nikon advises forget it. It could still work sometimes, but difficult AF cases likely fail to focus. You would likely lose some shots. Nikon is advising against this try. ALL LENSES with a maximum aperture of f/4.8 or more are said to be incompatible with the f/8 limits of AF focusing with the TC-1.7. For the TC-1.7, this is f/3.3 for camera bodies that can AF at only f/5.6 [/QUOTE]

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