Forget Sigma Art - This is Nikon Art

Started Sep 24, 2016 | User reviews thread
Marianne Oelund Veteran Member • Posts: 7,255
The Science Behind Nikon's Art

russbarnes wrote:

I used to hang my hat on DxO lens reviews but after a while I worked out for myself how incredibly one dimensional they were. On a site like that, the rendering intention and artistic draw of a lens is simply lost in numbers based on things like absolute centre sharpness and vignetting.

Nikon designers know EXACTLY what they're doing and for those that have worked out that absolute sharpness is not the be all and end all then artistic lenses like this and the Nikon 35mm f/1.4G are a match made in heaven.

Some think that somehow the 58 1.4 is over-priced, too soft, too random blah blah blah. To be fair mine requires a +14 AF fine tune adjustment on my D810 but I wonder how many people have torn shreds off the 58 actually spent some real time on things like AF adjustment to get it exactly right because when it's dialled in it could well be Nikon's most beautiful output yet.

I won't hesitate to recommend it to others, if you're interested in artistic photography ahead of anything else then this is a lens for you. If you're expecting it to be something like an 85mm f/1.8G (a lens I personally couldn't get along with) then you are going to be wildly disappointed.

I would like to point out some technical fine points, which I believe are important contributors to the 58G's imaging capabilities.  Let's go beyond what lens reviewers take into consideration, with a careful f/1.4 comparison of the Sigma 50 Art and Nikon 58G, within the critical transition zone.

Blur circle profiles, that is, the brightness within the COC across its radius from center to edge, are the basis of defocus image quality and the way the lens converts the 3D subject into a single-plane image.  Here are some examples of blur circles at close subject distance, which we can study in detail:

The first thing we look for, to produce smooth, soft background bokeh, is a blur circle with a nicely diffused perimeter - as opposed to a bright-ring perimeter.  We see that both the 58G and the Sigma achieve this, but the 58G has an even more expansive and diffuse outer circle.  No other lens that I have tested can achieve that to the same degree (other than a DC lens with extreme DC-ring positions), and this gives the 58G the smooth backgrounds that it is so well known for, in addition to its low-contrast "dreamy" look when used wide open.  Going beyond the obvious, however, I would like to look at some more unique aspects of the 58G.

1.  Central Concentration (background)

The 58G manages to place a considerable amount of light energy into the very center of the blur circle (some of the older designs also do this, but not to nearly the same degree).  This creates an ability to preserve visible detail, much further into the background than would be expected from typical DOF considerations.  Note that this central concentration remains quite sharp out to +40mm, and is still very small at +60mm.  Indeed, because of the central brightness, one would have difficulty deciding where the precise plane of focus is; focus at 0mm, +10mm or +20mm, although different, may all be considered "in focus" for various purposes.

2.  Near Foreground

Note that the Sigma, typical for lenses with some under-corrected SA, immediately forms a ring-type bokeh circle, apparent even at -10mm.  The interior of the blur circle is very dark, with almost all of the energy at the rim.  This type of blur circle creates harsh edges around bright points or lines in images, and a "doubling effect" around narrow lines such as grass blades.  It also acts to obscure detail and reduce apparent DOF.  The 58G, however, has been endowed with near-foreground bokeh circles with much more energy in the interior.  Although they do eventually hollow out at -40mm, the near-foreground blur quality will be much better.


The advantages of the traits described above will vary with the type of subject being photographed.  They are most easily seen with light details on a dark background, so let's take a look at such an example:

Both f/1.4, at equivalent distances, but note the difference in range of readable detail

More Visible Detail in Your Photo

Now we can see what the attributes described in 1) and 2) above are giving us in our images.  First of all, when the 58G goes out of focus, it does so without introducing ugly harshness at high-contrast edges; transitions are smooth and pleasant.

But the real benefit that I'm driving to with all of this discussion, is the amount of visible detail that will exist in the photograph.  We often say "very little is in focus" of our wide-aperture images due to the extremely tight DOF.  It would be a huge improvement, if there were some way to extend the visible detail beyond the usual DOF.

That is exactly what the 58G is doing!  Look at the scales in the Sigma example - how far from the focus point, can you still read the numbers, or see the separation between the mm markings?  Now examine the scale in the 58G example - you can read detail much further from the focus point.  There is a range of usable detail that would require stopping down to about f/2.8 with most lenses, yet it's an f/1.4 image with all of the desirable bokeh qualities that such an aperture brings.

This is quite a technical achievement - almost magical, I would say.

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Source credit: Prov 2:6
- Marianne

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