Over the course of the past few weeks I have had the chance to really get acquainted with this lens. Though not my first manual focus Nikkor (that honor belongs to the excellent 50mm f/2 AI), this has become a favorite of mine recently, tending to stay on my NEX-7 about 70% of the time. Despite its minor flaws (which will be discussed in detail), this lens is dynamite. After some personal confusion in figuring out just what the lens could be used for (the 157mm equivalent is technically too long for normal portraits, and too short for a normal long telephoto), I happily found that it is quite perfect for both “up close and personal” portraits, as well as a useful lens for separating people from a crowd. This is obviously afforded by both the large maximum aperture and the focal length; at f/1.8 and at 15 feet, the depth of field (the amount of distance perpendicular to the lens that is in focus) is just over 5 inches. This in effect allows for the subject separation in the below shot:

So let’s dive deep into all the aspects of this fine legacy lens, shall we?

Specifications

Full Title: Nikon Nikkor 105mm 1:1.8 AI-s.

Dimensions: 3.1 inches in diameter, 3.5 inches long, with a weight of about 20 ounces (8 ounces more than the camera itself!)

Close Focus: Marked at 3 feet/1 meter, but you can get just a bit closer. This is NOT a macro lens.

Misc: 9 straight-bladed diaphragm (stopping down to f/22), 62mm filter thread (metal), built-in telescoping lens hood (doesn’t lock into place, but is very handy).

The “Feel”

Based off the dimensions and picture as mounted on the NEX-7, it’s easy to see this is a chubby lens. This is a good thing, if you have big hands. The size of the lens is hefty enough for it to have a comfortable grip, especially given the size of the focus ring (which takes up almost half of the lens’ length). The weight also works in its favor, as since the entire kit is front-lens heavy, it naturally rests in the left hand, though it is still light enough to allow for one-handed shooting.

The construction is typical of Nikkor AI-s lenses, which have been previously described by others to no end as the pinnacle of lens craftsmanship. Everything, save for the glass and paint in the engravings, is metal. Everything. The mount, the barrel, the hood, the filter threads, you name it. Though I would hate to drop this lens on anything (or anybody), I’m sure whatever it hits would be in worse shape than the lens.

The focus is smooth and damped well, as it should be, seeing as focusing manually is the only way to use the lens!

Performance

Summary

As mentioned above, this lens is dynamite on the NEX-7. It performs well wide open (unique for its exotic f/1.8 aperture), and doesn’t have any problems out of the ordinary for a medium telephoto that are of any importance. Most importantly, it just feels right in use. If you can find one secondhand (they obviously aren’t made anymore) for under $500, and you want or need a fast lens for shallow depth of field work (or tack sharp peak performance at a wider aperture than most lenses), get it. You will not regret it. If you don’t want to worry with the review, just know that you cannot go wrong with this lens. Before I get started, take note that unless otherwise noted, none of the test pictures have been edited aside from cropping and resizing.

Sharpness

Though sharpness is supposed to be only a small factor in a lens’ performance, many feel it is the most important. I personally fall somewhere in the middle. I love seeing pixel-level sharpness, but it isn’t terribly important that all my shots are sharp when viewing at 100%. That said, the 105mm f/1.8 is extremely sharp, getting into razor-sharp territory at its optimum apertures. The test chart I have used for assessing sharpness is a free chart downloadable at http://www.pbase.com/iangreyphotography/lenstests.

All shots below were done on a tripod with a 10 second timer to ensure camera shake does not comes into play. These crops are at 100%, so there is no need to click on them, this is as big as they get. By aperture:

To sum up center performance, wide open and at f/2 there is some noticeable softness, and there is a lack of contrast. At f/2.8 it sharpens up nicely and gains great contrast. f/4-5.6 are pretty much the same and are the optimum apertures for sharpness and contrast. This is extremely pleasing, as this allows shorter exposures in all conditions for the center’s best performance, though is bad for those who want optimum sharpness combined with a greater depth of field. From f/8 on, sharpness and contrast are slowly and incrementally reduced, with f/22 being only marginally sharper and contrastier than wide open.

Next up, corner performance, all 100% crops from the upper left corner. By aperture:

In a nutshell: since this lens was designed to cover 24x36mm film, corner performance is expected to be stellar, as the smaller APS-C size sensor is technically using more of the center of the image circle. The good news here is the corners perform well for an extremely fast telephoto lens. From f/1.8-2.8, corners are mushy and soft. By f/4, it has sharpened up very nicely, and contrast is great. Amazingly, the corners have reached optimum sharpness and are the same at f/5.6-8. From f/11 on, the expected diffraction degrades image quality in steps, with the corners at f/22 ending up about the same as at f/2.8. Bottom line here, if you need corner to corner sharpness, shoot this lens at f/5.6; at this aperture both the corners and the center are optimum. This is stellar performance, as this aperture is at least twice as fast as the typical f/8-11 optimum aperture of zooms. Pixel-level sharpness at wider apertures is one important reason to own a large aperture prime, their optical performance in this category is nothing to sneeze at.

Sharpness at Infinity

In this boring far-away shot, critical sharpness is confirmed at the hyperfocal infinity distance. Interestingly enough, the limit to this shot’s sharpness is atmospheric haze, rather than anything with the lens:

Sharpness at Macro

As mentioned, the 105mm isn’t a macro lens. However, the close-focus distance of 3 feet is close enough to get within the range of “croppable-macro”. Since the lens is super-sharp at optimum, this cropability can be taken advantage of.

Bokeh

“Bokeh” is a Japanese term for the character of anything in the image that is not in focus. Typically, smooth bokeh, where out of focus objects and highlights seem to “melt” into the background, is favorable. For the most part, when used in the right circumstances (portrait distance of around 15 feet), bokeh is excellent. The achilles heel of this lens’ bokeh is in the rendering of out of focus highlights. They are not good. In an attempt to asses bokeh at various apertures in a controlled setting, I set up a series of objects with various characteristics, seen below:

Let us first take a look at bokeh smoothness. In the shots below (which are not 100% crops, but resized) the two dolls on the left are behind the plane of focus, while the two dolls to the right are in front of the plane of focus.

Basically, the background bokeh (the “important” bokeh, as having objects in front of the focus plane messes with our eyes) is very smooth. As objects get further away from the focus plane, they blur away into washes of color, without defined borders. The foreground bokeh is a little less pleasing, though is still relatively smooth until f/4, where it seems to feel “busy”, rather than smooth.

Now let’s examine the highlights. As mentioned, this lens doesn’t handle them so well, though it only becomes a problem at smaller apertures:

What’s good is at larger apertures, from f/1.8 (not shown as it is virtually the same as f/2) to f/4, highlights are not distracting and are smooth throughout the whole highlight. What’s bad is at every aperture smaller than f/4, the highlights start going from mediocre to worse, with halos and other strange artifacts filling the shape. It is worth noting that I am examining these very closely. This anomaly will only be noticeable when printing big. Where bokeh really matters though (f/1.8-4), this lens does just fine. My suggestion would be to just watch out for point light sources when shooting at small apertures! In the below “real-world” handling of bokeh with highlights, there’s nothing to worry about:

Purple Fringing

A form of chromatic abberation (a type of distortion where certain colors do not hit the image sensor at the same convergence point), purple fringing is typically seen in fast lenses at their wider apertures when shooting scenes of contrast, such as branches against sky. Though purple fringing can be cleaned up very well in post processing nowadays (see my detailed post on that here), it is still an important point to take in consideration if one either doesn’t have the time to post process, or has purple objects in the frame that does not want to be desaturated. To test for purple fringing, I shot a tree against sky in midday (for the most contrast), seen below. The crops will be taken from the center area:

By aperture, the following have only been edited to equalize general exposure:

As I stop down, the purple fringing is completely absent, as expected. If you take only one thing away from this section, don’t shoot trees at f/1.8-2.8 if you can help it.

Flare

To my knowledge, this Nikkor (along with all AI-s Nikkors) is multi-coated to help guard against lens flare resulting from internal reflections from strong light sources. The coatings seem to work very well. In an attempt to exacerbate the problem, I shot a couple pictures stopped down (the aperture doesn’t affect flare in this instance) towards the sun with the hood extended. WARNING: the only reason I could get these shots is that the NEX-7 uses an electronic viewfinder. If you try to do the same on a DSLR with an optical viewfinder you may blind yourself, so be careful! In this first shot, with the sun just barely out of the frame, I see no obvious reflections from the elements themselves, only veiling flare is noticeable that is keeping the sky from being truly blue:

However, once the sun enters the frame, all havoc breaks loose, with obvious internal reflections seen:

As the sun (or a strong light source) gets towards the center, there are more lens reflections:

Bottom line? This is not the lens to use for shooting the sun. Plain and simple. Try to keep it, and other strong light sources, out of the frame if possible.

Vignetting

Vignetting, to put it simply, are darkened corners as a result of shooting near the wide open aperture. One of the other sweet spot advantages when using a “full frame” lens on an APS-C sensor is the relative absence of vignetting. This applies to the 105mm f/1.8 wide open and at any other aperture. There is no vignetting to speak of.

Distortion

Though I do not have a formal grid-lined chart to measure this exactly, I can’t notice any distortion either way, barrel or pincushion. Great news for architectural photography, or any other instance that you would love to have perfectly straight lines.

Now let’s hit the old recap.

Pros and Cons

Pros

• Extremely useful intimate portrait length, with an effective large aperture for amazing depth of field control
• Lens build is beyond solid, and a joy to use
• Sharpness and contrast peaks extremely high for center and corners at f/5.6, but the center is very useable wide open
• Background bokeh is pleasantly smooth and non-distracting
• There is no vignetting to worry about
• There is no distortion
• Lens is over twice as fast as any professional 70-200 zoom, but is much smaller and lighter

Cons

• Mushy corners at wide apertures
• Foreground bokeh is mediocre, and out of focus highlights are not handled well at smaller apertures
• Terribly bad purple fringing wide open with high contrast objects, though is not noticeable with normal subjects such as people. If this lens had an ED element this issue may have been less distracting
• Flare with the sun right next to the frame is okay, flare with the sun in the image is bad
• Not cheap
• Manual focus (not particularly a con, but just throwing that in there)

The Bottom Line

If you can hunt down a good copy of this lens on eBay, want or need this focal length for your own creative purposes, value top quality lens craftsmanship, and desire superb depth of field control, don’t hesitate to pick one of these lenses up. You will not regret it.

All the best folks, thanks for bearing with me in the time it took to write this. 🙂 As always, have a great one.