62 mm filters on the new 70-200 f/4 VR

<p>Having 62mm accessory filters like the Nikon circular polarizer and 6T close up lens, I gave each a try on the new 70-200 f/4 VR with a 67-62 stepdown ring. I was pleasantly surprised that either worked without vignetting on my D800 in FX mode wide open and all the way down to f/32 regarless of focal length. Not only that but I also had a 67mm UV filter attached for all tests.</p>

<p>Even though there is no "vignetting," those 62mm filters may still be obstructing the optical path and therefore are degrading image quality.</p>

<p>For what it is worth: the (old) AF-D 70-210mm Nikkor had 62mm filters. Progress makes 67mm filters the norm on some new(er) lenses.</p>

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<p>Doesn't using a smaller diameter filter reduce the effective f/stop especially wide open?</p>

<p>Well, i guess turn off Vignette Control, take 2 identical shots @70mm, one with and one without and <strong><em>critically</em></strong> examine the corners. If there's absolutely no difference carry on.</p>

<p>It's all cones rather than cylinders and 'most' front elements don't reach to the edge of the lens barrel by some margin, some by well over 2cm each side, especially the wide angles (to prevent vignetting!) ie the 18-35mm 3.5/4.5.</p>

<p>Longer lenses have a much narrower cone, so can tolerate <strong><em>minor</em> </strong>filter diameter reductions....I'd guess a 58mm would be in trouble!</p>

<p>_______</p>

<p>Curious, if there's no vignetting, ie corner difference can't be detected on the sensor/image, what kind of optical-path obstruction leading to image degradation can there be? I do have a very vague memory of school experiments with a ripple tank and the waves kinda bend after going past an obstruction and that's the cause of erosion on harbor bottoms around the end of breakwaters.</p>

<p>I've had a 62mm f4, a 58mm f4 and a 58mm f3.8 ... I'd love to know what the designers do with those extra millimetres.</p>

<p>when those 2 element Nikon close-up filters came out, it was common usage to put them on lenses one common filter size up if the lens was telephoto. I even remember people putting the 62s' on 72mm lenses. </p>

<p>Testing for corner falloff at 70mm and vignetting control off using either a 62 Polar or 6T achromat close-up lens revealed no additional falloff compared to what naturally occurs when no filter is attached.</p>