Questions About The Nikon AF DC-NIKKOR 135mm f/2D Lens
Mar 6, 2017 17:41:50 #
Gene51 wrote:
Don't have one. Great lens. Don't know anything ab... (show quote)
Fabricated personal discussion based on gratuitous commentary is not "just having some fun". It's a display of envy similar to stalking and has no place in a technical discussion that should be on a level of high integrity.
Mar 6, 2017 20:13:40 #
Mac, since all the examples here apparently have been shot at f/4 or greater I shot a few comparison shots with mine today.
The first sample shows f/2, f/2.8, and f/4 comparisons. DC not used. All were shot at very close to minimum focus distance on a tripod. The distance from focus point to background lights was about 5 feet or a little less.
The second group were all shot at f/4. I used DC as indicated. The ones marked R8? and F8? were in the unmarked slot beyond the 5.6 indicators on the DC control ring. R and F indicate Rear and Front defocus. In the second group the lights were only 3 feet behind the focus point. You can judge if you think the effect is significant or not.
The first sample shows f/2, f/2.8, and f/4 comparisons. DC not used. All were shot at very close to minimum focus distance on a tripod. The distance from focus point to background lights was about 5 feet or a little less.
The second group were all shot at f/4. I used DC as indicated. The ones marked R8? and F8? were in the unmarked slot beyond the 5.6 indicators on the DC control ring. R and F indicate Rear and Front defocus. In the second group the lights were only 3 feet behind the focus point. You can judge if you think the effect is significant or not.
Mar 6, 2017 20:40:42 #
I noticed that the f/2 to f/4 sample above shows a nice representation of the bokeh difference at the different apertures, but not really the detail difference at the focus point. To show that f/2 is really a bit soft you need to look at the fine detail differences on the usb thumb drive in this image.
Mar 7, 2017 09:52:55 #
aflundi
Loc: Albuquerque, NM
aflundi wrote:
I can't say I followed your explanation. 
Are you saying that the plane of focus actually shifts away from the PDAF point toward one DoF bound or the other at the same time and in addition to the SA corrections? And that the DC lens has DoF builtin, and therefore an assumed CoC -- presumably for FF -- in order to know where the DoF bounds are? [ ... ]
Are you saying that the plane of focus actually shifts away from the PDAF point toward one DoF bound or the other at the same time and in addition to the SA corrections? And that the DC lens has DoF builtin, and therefore an assumed CoC -- presumably for FF -- in order to know where the DoF bounds are? [ ... ]I assume that when SA over/under correction happens, the point of best focus will shift. I had assumed this would be a small effect compared to the DoF. However, after thinking more about it, and seeing pictures with DC adjustments (including the ones Rick36203 provided), it looks to me like the SA correction focus shift may well be comparable in size to the DoF rather than much smaller.
Is it possible that that is exactly what Floyd (apaflo) described, and that Nikon in making the lens, put markings on the DC adjustment such that the SA correction shift corresponds to the DoF bounds or some practical, reasonable, large percentage of the way to the DoF bound? If so that would tie everything together quite nicely, and make it all easy to understand and use -- at least conceptually
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