Nikkors f/1.8D | f/1.8 AI-S "long nose" | f/1.4 AI-S
When looking at getting a 50mm f/1.8 AI-S, its already confusing giving the difference in the range of lens. The key 50mm AI-S:
- 50mm f/1.8 AI-S long nose
Shortlived ~5yr production run from 1981 succeeding the AI, worldwide export, full metal body, 0.45 min focus distance, narrow 2-row aperture ring and recessed element/stepped front and rabbit ear prongs - serial numbers 3xxxxxx. So called "long nose" because of the longer barrel (and recessed front element) compared to the latter and flatter iterations of this AI-S lens. - 50mm f/1.8 AI-S Pancake with short MFD
Japan only, full metal body, 0.45m min focus distance, narrow 1-row aperture and 1-row focus rings, no rabbit ear prongs - serial numbers 205xxxx. See Nikkor 50mm f/1.8s Mark II documentation. - 50mm f/1.8 AI-S Pancake
Final iteration of this AI-S lens with production running til 2005, metal and plastic body, 0.6m min focus distance, narrow 2-row aperture and 1-row plastic focus rings, no rabbit ear prongs - serial numbers 40xxxxx
(c) Richard de Stoutz
There were also the Series-E 50mm f/1.8 that had different optical formulas and black platic and chrome grab rings.
Bjorn Rorslett believes the optical formula changed between these 3x AI-S lens and even the 50mm f/1.8D - Nikon's literature shows that they seem to have the same optical structure but its clear they have different coatings.
Initial handling of the long nose can take a moment to get comfortable as you will be surprised by the narrow 2 row aperture ring which is the same as the f/1.8D - muscle memory makes you want to grab further forward. The long nose focus ring, whilst also narrower is still large enough to use without too many mis-grabs whilst the 1 row f/1.8D can again take a bit of time to get used to. As with the majority of the AI/AI-S lenses, they simply handle better than the AF-D lenses which moved to plastic and composites along with crinkle finishes for the lens barrels: both the AI-S and f/1.8D are smooth. The AI-S being manual focus has a longer focus which smoother and feels more substantial thanks to the brass helicoids compared to the plastic of the f/1.8D, which in fairness can be driven by a screwdrive in-body motor: using both on the mirrorless Nikon Z-cameras would mean both are manual focus.
In terms of optical output, they are close. The coatings are different compared to the f/1.8D, with the latter having coatings giving similar redish-brown sheen seen on other AF-D lenses of the time. I am pleasantly surprised at how good the f/1.8 AI-S is wide open as below - there is some CA in high contrast areas but its not overly bothersome and one click down its enough sharp.
AI-S @ f2 - crop of head/shoulder
AI-S @ f/1.8 - focus on bottom left of parallel lines
AI-S @ f/1.8
AI-S @ f/2.8
Furthermore, all of the product photos of the 180mm f/2.8 AI-S were taken with the 50mm f/1.8 AI-S at f/4.
Bokeh is smooth wide and relatively non-instrusive:
AI-S @ f/1.8 - close to MFD
AI-S @ f/1.8 - focus at ~1.5m
Backlit images aren't a big problem, although in studio with white background I did notice some drop off due to flare but the following images show how resilient this lens. Trying to reproduce ghosts and flare surprisingly takes effort, even when the sun is directly in the frame
AI-S @ f/2.8
AI-S @ f/1.8
Surprisingly its size if not too dissimilar to the 50mm f/1.4 AI-S in weight, with about 30g difference.
Sharpness Compared
Here, we're not only comparing 3x different lenses but also 3x different optical formulas, since the f/1.8 AI-S long nose vs f/1.8D (which has lineage back to the f/1.8 AI-S pancake/series E).A static scene lit with the same flash at 1/250th and manually focused using live view focused (on the lettering of the lens cap) with camera sat on tripod is used for our sharpness comparison: the focus distance is about 4ft or stanard portrait-like distance away. The white balance has also been corrected so we remove the issues with minor colour rendering of the lenses. The below items are centre crops of the larger image.
Wide open
The f/1.4 AI-S is known for its apparent softness wide open with reflected light and we can see the veiling flare. At a 100%, this still appears sharp but the CA do obscure this. The f/1.8 AI-S suffers less CA (more noticable on 100% below but also see previous images above) but its still present - the f/1.8 AI-S is sharper than the f/1.8D wide open but the f/1.8D appears to have better contrast.
Top - bottom, wide open - 50mm f/1.4 AI-S | f/1.8 AI-S | f/1.8D
At f/2.0
The f/1.4 AI-S is clearly the sharpest, but it is also 1 full stop down from max aperture where as the others are only stopped down a 1/3. The f/1.8 AI-S still betters the f/1.8D but only just.
Top - bottom, @ f/2 - 50mm f/1.4 AI-S | f/1.8 AI-S | f/1.8D
At f/2.8
The f/1.4 AI-S still remains the sharpest but now its a little closer between the 3 lenses. The f/1.8 AI-S still betters the f/1.8D but its even closer between the two f/1.8 lenses.
Top - bottom, @ f/2.8 - 50mm f/1.4 AI-S | f/1.8 AI-S | f/1.8D
Compared to the 50mm f/1.8 AI
The direct predecesor to the 50mm f/1.8 AI-S was the AI which was produced between 1978-81 and Roland Vink notes they share the same optical formula, although I do notice a slight difference in lens coatings.
L: AI, R: AI-S
Whilst they look very similar, baring the telltale orange vs blue f/22 marking, you can also observe the distance scale lettering on the AI version is larger: subtly, the aperture ring of AI-S is also narrower with 2 rows instead of the 3 rows. Internal construction is different (important for cleaning and servicing) and more akin to the 50mm f/1.4 AI where the AI variants have a much longer focus throw which might be appealing to some.
Note the reasonably well controlled CA and reasonable sharpness in the centre even when backlit.
50mm f/1.8 AI at f/1.8
Cleaning
Servicing the lens and cleaning the lens elements should be relatively straight forward, although I've found the bayonet screws and the optical groups sealed very well. Access to the front group is via a set screw to allow you unscrew the front barrel to reveal the spanner holes to access the front optical group. The rear group of 2 elements is sealed with a retaining ring. As usual, Richard Haw's site covers this well. The 50mm f/1.8 AI's optical elements are easier to access as they are housed in one lens objective that separates from the lens barrel but for the AI-S the lens elements are removed it sections.
(c) Nikon - representative 50mm optical cross section: number of elements and arrangements are the same as the "long nose" but not exact optical cross match
Access to rear optical elements
If you find your rear bayont screws are stripped, there is another method to access the rear elements: the black flange in the bayonet mount is secured by 3x screws which can be removed to expose more of the retaining ring - this in turn will allow you access to run acetone and IPA to break down to the threadlock (I placed a thin screwdriver with the tip touching the sealant and a few drops of solvent will get to the area required), after which you can use a rubber tool or rubbber gloves to remove the retaining ring and then access to the elements.The rear-most element can be picked off or with a lens sucker but be careful of the spacer underneath and its orientation after which you can remove the the couplet (4th/5th element) with a lens sucker.
top: L-R - removal of flange screws, removal of flange, exposure of retaining ring | bottom: L-R rubber tool orientation to remove (press narrow end to retaining ring), removal of retaining ring, top view with removed flange and retaining ring
Access to front optical elements
The front 3 elements are secured by a baffle that needs to be unscrewed with a rubber cone tool which will expose the front element. The other elements need to remove the front optical unit which is secured by the front name ring before using a lens spanner. Once the optical unit is removed, you will have access to the rear (3rd element) that needs to be spun off to access to the 2nd element (from the rear).
Summary
To be quite honest, theres little to choose between the 3x 50mms in discussion when it comes to optical quality. We know the f/1.4 AI-S has the 2/3rd stpp speed advantage, sharper rendering at equivalent apertures, and the slightly better bokeh (subjectively) wide open it suffers from glowing highlights/abberations which the f/1.8 AI-S and f/1.8D do not. At f/2.8 and up they're pretty much doing the same thing and so the decision for picking up either lens for me becomes a handling issue: the f/1.8D is noisey and the front focus ring spins vs the manual tactile feedback of the 2x AI-S lenses. Between the AI-S lenses in question it again becomes a toss of the coin for how much more the 2/3rd of a stop and options for the f/1.4's bokeh. There really isn't a bad choice here - the only surprise for me is literally how good this f/1.8 AI-S really is.
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