Part 2: Resolution tests of the AF-S Nikkor 24-120 f/4G on my D800

<p>Seen here: <a href="../photodb/folder?folder_id=1029934">http://www.photo.net/photodb/folder?folder_id=1029934</a> are additional shots taken with the 24-120 on my D800 at 24 mm and 120mm. Like 105 mm, the corners are less soft than the edge. Focus was set on the center target for all shots. Given the relatively slow lens speed of f/4, the extra distance of 7"/9" for the edge/corner target are well inside the 36" dof at the 24 mm setting and therefore was not refocused for those targets. ISO 100 was used. Image size was set to L (large) with Fine quality JPEG. RAW (not shown) was marginally better. All shots were made with auto distortion correction set to "on" and vignetting compensation set to normal. Regarding my previous comments on resolution less with auto distortion correction, they were erroneous. Re-shooting on auto distortion correction this time revealed only minimal resolution loss and therefore I feel it's best to leave this feature on full time as this lens does have noticeable distortion without it. The only post process manipulation was adding auto color correction making them appear whiter and brighter but does not affect the actual resolution.</p>

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<p>Given the relatively slow lens speed of f/4, the extra distance of 7"/9" for the edge/corner target are well inside the 36" dof at the 24 mm setting and therefore was not refocused for those targets.</p>

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<p>The result of this assumption (not wrong btw) also indicates that any softness is as likely to be due to field curvature as anything else. In other words, because of the curved field of the plane of focus, the edges might be outside the plane.</p>

<p>Looks like f8 and be there really works for this lens. Soft in the corners at the extreme long end? To be expected on a zoom, no? Again, I don't think this lens looks to be such a bad performer, based on your tests.</p>

<p><em>"I feel it's best to leave this feature on full time as this lens does have noticeable distortion without it"</em> I am not positive but I believe if you use third party software to process RAW files, this and other propitiatory corrections are ignored. If you are a JPG shooter, these settings should indeed be on.</p>

<p>Elliot, I agree, if you have the time and image quality has to be of the highest order, obviously RAW does produce the best results with this camera but not by a whole lot more if we are only talking about resolution. RAW is still king for dynamic range and other aspects. However, compared to the D700, JPEG right out of this camera is vastly improved and not far behind RAW. On the D700 the difference between JPEG and RAW was more obvious. Not shown here (maybe part 3 on a future post) were the results in DX @ 120 effectively giving 180 mm). They were pretty good wide open at around 50 lp/mm across the frame and stopping down 1 or 2 stops gave 56 lp/mm centrally and at least 50 lp/mm at the corner and edge.</p>

<p>Peter, while f/8 appears peak for resolution, f/5.6 was within spitting distance in terms of resolution. It might be a better choice in marginal light if you want sharpness, using lower ISO and slightly greater isolation of focus (although nothing beats a premium fast zoom or prime for isolation).</p>

<p>Thanks for posting these tests, they speak for themselves for this $1300 lens.</p>