Joe Photography: Nikon Lens Technology

Nikon is the leader when it comes to compatibility among cameras and lenses of different decades. Most of today's lenses are compatible with ancient cameras, and most ancient lenses can be made to work fine on today's digital cameras.

The key is to understand Nikon's alphabet soup. Each time they add a new lens feature they usually retain the previous lens features, so the newest lenses have long lists of letters behind them. One usually can ignore the earlier letters, even though they still apply. As we will see, today's AF lenses are still AI-s and F mount, even though they don't always list that.

The only two gotchas in 50 years have been in 1986, when AF lenses lost the prong needed to couple to pre-1977 cameras. No big deal, even today you can have prongs added. The only real gotcha has been with G lenses, which are just about useless on manual focus cameras. More at Nikon Lens Compatibility.

Some Nikon designations are mechanical, like F, AI, and AF; while others are optical, like ED and IF. We'll cover al of these.

Mechanical History

F (also called pre-AI and non-AI): 1959 top

Nikon 50mm f/2

Nikon Nikkor-H 50mm f/2. (circa 1969)

Non-AI, Pre-AI (also called NAI) refers to the original Nikon F bayonet lens mount and lenses introduced in 1959 for the Nikon F camera.

These lenses have an aperture coupling prong just below f/5.6. When used on cameras made before 1977, you had to "index" the lens to the camera's meter by mounting the lens and then remembering to rotate the lens to its largest aperture and back (f/2 in this case) so that the meter was properly calibrated. Forget to do that and your exposures could be way off.

You can recognize these first lenses from:

1.) Solid coupling prong.

1.) No coupling ridge on the bottom of the aperture ring.

2.) No second set of tiny aperture numbers on the aperture ring.

This primitive form was used through 1977, when the completely compatible AI series was introduced. All modern Nikkor lenses, except the G, are still completely compatible with the very first Nikon cameras, given a little machine work in some cases.

These lenses today can mount just fine on today's cameras if you first have them converted to AI by a machine shop, although you won't get matrix metering on the FA or F4 or AF cameras. See the AI section for more info. John White does great conversions and his site provides lots of background on AI lenses.

Most all of these lenses had automatic diaphragms. The diaphragm is held open against spring pressure while you are viewing the image. When a photo is taken that lever in the camera releases this pin. The lens very quickly stops down to the aperture you have set on the lens (or set by the camera's automation), until the pin again is pushed by the camera to open the diaphragm after the photo is made.

Fig. 1.) Automatic diaphragm pin

For meter coupling an AF lens to a pre-1977 camera you will have to have Nikon add a prong to the aperture ring. You'll see two little pilot holes around the f/5.6 position for the screws!

Nikon's later cameras were still able to accommodate pre-AI lenses. Nikon's FE, FM and F4 bodies had special aperture coupling rings that let these lenses mount, but metering was via stop-down.

As a testament to Nikon, my new 2007 Nikon F6 can be retrofitted with one of the special rings that lets it also use these lenses from almost 50 years ago, and the F6, with stop-down metering and the AE-Lock button, still meters and gives aperture-preferred automation. Bravo Nikon!

These lenses also mount on the cheaper digital SLRs like the D40, D40x, D70 and D80, but have to be used by guessing the exposure since the meters don't couple.

AI (Automatic Indexing): 1977 top

Nikon 50mm f/1.4 AI

Nikon Nikkor 50mm f/1.4 AI. (circa 1979)

This was a real advance in 1977. For once you could mount lenses with one twist, and NOT have to twiddle the aperture ring separately each time. Since indexing was now automatic and foolproof, it was called automatic indexing or AI.

An AI or (AI converted) lens still works wonderfully today on Nikon's newest D300, D3 and F6 cameras. Mount these lenses on a D300 or D3 or D2Xs etc., enter the lens' information manually, and you now get matrix metering and EXIF data!

You can recognize AI lenses by:

1.) Coupling ridge on bottom of aperture ring. (look near f/8 on the 50mm lens above.)

2.) Second set of tiny aperture numbers which, on better bodies, allowed you to see the aperture in the viewfinder with a set of tiny lenses that looked out at them. This finder readout is called ADR, for aperture-direct readout, and the scale of small numbers is called the ADR scale.

3.) Two extra skeleton holes in the coupling prong to let light hit f/8 and f/4 so they are easy to read in the viewfinder.

All AI lenses are also F mount lenses and fit onto every Nikon SLR camera ever made. The cheaper AF and digital cameras lose metering ability with these manual focus lenses.

Used AI lenses are bargains. They are mostly the same as the newer AI-s versions made today, but you can get them less expensively. Today AI lenses can be bought very cheap, and they are often far better made mechanically than many of even the "professional" AF lenses of today. There are no different significant features available between AI and AI-s lenses. The only functional difference is if you have an FA camera, on which only AI-s lenses of 135mm and longer will automatically trigger the high-speed program. AI lenses will all work on the standard program, which I prefer anyway.

All AI lenses give matrix metering only on the F4 and FA, as well as all Manual, Shutter-preferred (S), Aperture-preferred (A) and Program (P) modes on the FA. Forget it on any other modern AF cameras.

These manual focus lenses only give give center weighted and spot metering in manual and A modes on most AF cameras.

The AI mount even includes (to this day) mechanical lugs that tell the camera the focal length of the lens. Nikon snuck that in there for future cameras that may have taken advantage of that, but none of those cameras were ever built. Today all this information is coupled electronically to the AF cameras by AF lenses.

The AF cameras do not read these lugs, because it costs more to put mechanical feelers in the camera. That is the reason you can't get matrix metering with manual focus lenses on any AF camera except the F4. It's also the reason some AF cameras can't even meter with manual focus lenses. It's just because Nikon cheaped out, preferring to have you have to buy new AF lenses instead.

To Nikon's credit, newer lenses usually always work with older cameras, but newer cameras don't always work with older lenses.

See more about use on AF cameras here

AI Updates, Conversions and Hacks: AI'd or AID top

Correct Factory Upgrades

Back in the late 1970s and early 1980s, Nikon would upgrade pre-AI, also called non-AI, lenses for about $20 each so they would work with the new AI compatible cameras. Nikon did this by designing brand-new aperture rings dedicated to each lens. When you sent a lens to Nikon, they replaced the old aperture ring with a brand-new factory part. These new parts were designed to match the cosmetics and color-coded apertures of each lens.

These factory upgrades work perfectly.

An example of an old lens with a newer, factory retrofitted AI ring looks like this:

Nikon 35mm f/2.8 AID

Nikon Nikkor-S 35mm f/2.8, factory AI conversion. (circa February 1968, converted later)

The way to identify a factory AI conversion is to realize that this lens was from before the AI era, and note that the aperture ring has flutes to match the early focus ring. Nikon did a class job. Except for the obvious anachronism of the AI ring on an older lens, everything else about the lens is original.

Nikon no longer offers these upgrades, but if you can find the part for your lens, you can have it installed and you're all set.

Converted lenses are factory-approved, and collector-approved, too. Lenses converted this way work great with the latest F6, D300, D700 and D3, which adds to their collectible, as well as user, value.

Home-Made Hatchet- Job Conversions

Since Nikon no longer does these conversions, some people get out their metalworking tools and hack away at the aperture ring to get some sort of crude functionality. This lets them work on newer cameras, but destroys any value they may have had to collectors. Any lens that's been converted has no collectible value.

To do this, people grind off some of the bottom of the aperture ring and maybe glue on an ADR scale. Here's what a good one looks like:

Nikon 200mm Q

Nikon Nikkor-Q 200mm f/4, home AI converted. (circa 1971, unknown conversion date)

You can identify the non-Nikon AI conversion by:

1.) The coupling ridge is really just part of the aperture ring, ground off.

2.) Glued-on paper ADR scale.

3.) Still has solid prong with no holes for the light.

Older non-AI lenses converted to AI will not give matrix metering on the FA and F4 unless one adds the special absolute aperture coupling lug to the mount, something that is not part of the usual conversion. I did add this to a 200mm f/4 Q and a 300mm f/4.5P, but these are probably the only samples of old converted lenses on the planet that give matrix metering with those cameras.

Today John White does these conversions to update pre-1977 lenses for use on almost all of today's Nikon cameras.

Nikon Series E: 1979 top

Up through the 1970s Nikon only made very expensive professional lenses. Normal people had to buy discount brands lenses if they wanted something they could afford. Buying an off-brand lens was, and still is, the worst of all worlds: spending a lot on a camera, and then getting a dinky lens. The lens is the only part that affects the picture quality, so you are far better of with a crummy camera and good lenses.

To capture more of the amateur market Nikon decided to make a series of lenses called "Series E" which had great optical quality. They were built with well thought out, simple to manufacture optics and cheaper mechanics that were more than good enough for amateur use. These cheaper mechanics are often better than what Nikon makes today in some of their cheaper plastic AF lenses.

The optics are all great. Nikon only made Series E lenses in focal lengths and aperture ranges for which optics could be designed simply and still give great performance. For instance, I have the 100mm f/2.8E. A 100mm f/2.8 lens is very easy to make work very well for very little money. It is as sharp or sharper than my expensive 105mm f/2.8 AFD micro and 80-200mm f/2.8D AF-S especially at f/2.8. An 80-200mm f/2.8 zoom has to be expensive because it requires complex optics, but a fixed 100mm f/2.8 lens is easy to make inexpensively. Take these series E lenses very seriously.

The simplest Series E lenses were single-coated and others were multi-coated. Nikon's designers knew what they were doing: they used whatever they needed. The very simple classic designs of some of the fixed focal length Series E didn't need multi-coating.

The first Series E were a little bit ugly. The first were mostly black (lacking the chrome colored grab rings of the Nikkors) and used dorky big blocky nubs on the focus rings. In a few years Nikon updated the cosmetics and added the silver colored aluminum grab ring near the aperture ring and nicer looking nubs on the focus ring rubber, making them look very similar to the Nikkors.

These great lenses were never popular because Nikon was too honest.

Back then Nikon admitted that they used a little plastic here or there in the Series E lenses, which at the time was considered a crime. Remember everything is made of plastic today but back then everything was metal and weighed a ton. Nikon didn't use the Nikkor brand name because they were reserving the Nikkor brand only for what they considered professional lenses. Therefore everyone was afraid of the Series E lenses and few people bought them. Oddly, more people bought the crummier cheap brands that weren't as honest about what they were selling. Too bad, because the Series E were great lenses and far better than the discount ones. Today most Nikon AF lenses are far more cheaply made than the Series E were, and they are called Nikkor. Heck, even some of the super-expensive AF-S lenses have PLASTIC filter threads, and the Series E were solid metal.

From what I've seen Series E lenses typically had anodized black aluminum barrels and focus helicoids instead of enameled brass barrels and brass helicoids as the manual focus Nikkors do. All Series E had metal mounts, although some had plastic focus helicoids. They had aluminum zoom cams. Today's cheap AF Nikkors have plastic mounts and very little metal anywhere. The Series E have plastic aperture rings, a crime in their time but standard on almost every expensive Nikon lens today. The series E were very precisely made mechanically.

Some Series E optical designs were used in newer AF-Nikkor lenses. For instance, I read that the first 28mm f/2.8 AF and AF-D Nikkor sold up until about 2001 was the Series E five element design, and that the 70-210 f/4 AF was the 70-210 Series E design.

The Series E retained Nikon's superior seven-bladed diaphragms.

All Series E lenses are AI-s, and likewise fit every Nikon SLR camera, manual and auto focus. Some of the cheaper AF cameras and the D100 lose the ability to meter with the Series E as they do with all manual focus lenses.

See more about use on AF cameras here. The operation and compatibility of the Series E lenses is identical to the other manual focus AI-s lenses, which makes sense because they are AI-s.

In 2007, Nikon is re-using the E designation to refer to the electronic diaphragm of their PC-E lenses.

AI-s: 1981 top

Nikon Nikkor 28mm f/2.8 AI-s. Note two orange f/22 markings.

This was an incremental advance in 1981. It is the same as AI unless you have an FA or F4.

You can identify an AI-s, as opposed to an AI, lens, by:

1.) The smallest aperture (largest number, f/22) on the ADR scale (the second set of tiny aperture numbers) is in orange.

2.) You'll see this half-round cutout in the mount:

Nikon AI-s gouge

Fig. 2.) The gouge in the center of the photo tells some Nikon cameras that this is an AI-s lens.

AI-s is over 20 years old and still the version made today for manual focus lenses.

AI-s is the same as AI-S. I've seen it written both ways.

The other two ways to identify AI-s as opposed to AI are:

1.) AI-s lens' minimum aperture (usually 16 or 22) is marked in orange.

2.) Color-coded depth of field index lines are engraved on a thin chrome ring, unlike on AI lenses where they were engraved on the black painted part of the lens.

The "s" means that the actuation of the diaphragm was linearized with respect to the position of the automatic diaphragm pin. This is very important for AF cameras because they have have open-loop exposure control that depends on the aperture being exactly correct or else your exposure will be off. It is not important to manual focus cameras. (see "Aperture Calibration" below)

Some manual-focus, auto-exposure cameras like the FA use closed-loop exposure control. That means that they make the actual exposure measurement in the instant AFTER the lens stops down but before the mirror flips up, and means that they will automatically compensate for any inaccuracy in the lens diaphragm actuation.

Adding linearization to the actuation made it possible for these cameras to work a little more quickly when you pressed the shutter. It allowed the camera to get to the intended aperture a little faster, since it could guess pretty well where the diaphragm control pin needed to be and just go there, instead of having to release that pin a little more slowly while monitoring the light through the lens to arrive at the intended aperture by successive approximation.

All this happens in thousandths of a second, and I've never felt any speed difference on my FA between AI and AI-s lenses. The difference would be in the lag from when you pressed the shutter to when the film gets exposed, and it all seems pretty instantaneous to me.

Today some people think that AI-s lenses are required in order to get shutter-preferred (S) and program (P) modes on cameras like the FA. Nikon salespeople tried to suggest this casually as a ploy to get people to replace their AI lenses with new AI-s ones, and this myth still exists today.

Baloney. All AI, AI-s and AI-converted lenses work fine on the FA and similar manual focus cameras from the 1980s. Ignore me, see your camera instruction book. They all, to this very day, have detailed charts that explain exactly which features work with which lenses on your camera. Yes, you can get full program mode on the FA with a lens from 1959 that has been AI converted, even though you won't have matrix metering due to the conversion.

The sales brochures always choose to ignore telling you which features you lose with certain lenses (like the fact that new AF-S lenses can't autofocus on many popular cameras like the 8008), however the actual manuals are always honest.

All AI-s lenses are also AI lenses.

All AF, AF-I and AF-S lenses are also AI-s.

All AI-s lenses fit on every Nikon SLR camera, including AF cameras. Some of the cheaper AF cameras will not meter with these manual focus lenses. Also AF cameras don't do much with manual focus lenses. See your camera's instruction book.

See more about use on AF cameras here

AF (Autofocus): 1986 top

Nikon's traditional AF lenses are focused with a mechanical coupling between camera and lens. There is a screwdriver thing that pokes out of the camera like the Alien and couples with the slotted rotating coupling shown below. It rotates to move the lens in and out for focusing. Today it's primitive compared to the Canon AF system, however back in the 1980s it allowed Nikon to retain compatibility with the manual focus lenses.

Fig. 3.) The slotted screw in the middle of this photo is turned by an AF camera to focus the lens mechanically

All AF lenses are AI-s, and work great on manual focus cameras. You'll need to install a meter coupling prong for use on pre-AI cameras.

Aperture Calibrations top

Manual focus lens' diaphragms are usually adjusted correctly at the factory and usually more than accurate enough for life. Only if you have had the lens serviced are you ever likely to see a problem. The aperture you select on the ring is usually the aperture you get.

AF cameras control the aperture by varying the precise position of the spring-loaded automatic diaphragm pin that pops out of the back of the lens. The correlation between this pin's position and the opening of the diaphragm also needs to be adjusted correctly. This is a separate adjustment from the the correlation between the aperture ring and diaphragm noted above. Any slight variation in this internal adjustment will vary the exposures you get with that lens. Therefore, some lenses may give slightly different exposures than others. This is a limitation of the Nikon AF system with which Nikon is stuck because they base their AF system on compatibility with manual lenses. Canon controls all this electronically.

I say "stuck" because the mechanical tolerances are quite tight and can lead to a third stop variation here and there.

You can try looking at this yourself. Look through the lens on an AF camera. There ought not be any aperture blades visible. Now go to M or A modes and select different apertures. Press the DOF button on a modern AF camera and see what happens. When you set the maximum aperture of the lens you ought not see any blade motion. At the first 1/3 stop down setting you ought to see a little bit of blade motion. At the next 2/3 stop down you ought to see twice as much.

For instance, with an f/2.8 lens set at f/2.8 you should see no motion of the diaphragm when set to f/2.8 on the camera. Set the camera to f/3.2 and you ought to see them move a little bit when pressing the DOF button. Now set f/3.5 on the camera and you should see twice as much motion.

If you see a lot of motion, even at the lens' maximum aperture, you may tend towards underexposure.

If you see no motion unless the camera is set to a couple of third stops down from maximum you may tend towards overexposure.

Unless you are a camera designer don't fret over this. A far better way to test this is to go photograph on slide film with two or more lenses you wish to compare.

The diaphragm ought to be in the same place when set to the same aperture on the lens, or on the camera.

Many zooms move the diaphragm while you zoom. It is often normal to see a bit of diaphragm even when set to maximum aperture at some ends of the zoom range.

AI-P: 1988 top

This was a kludge invented around 1988 to allow Nikon to milk a little more life out of some of its manual focus telephoto lenses before it could develop AF supertelephotos. In 1988 the longest AF lens Nikon made was a 300mm f/2.8.

P lenses are manual focus AI-s lenses that have had the electronic contacts of an AF lens added to them.

There are only a few of these: the 500mm f/4 P from 1988, the 1200 - 1700 mm f/5.6-8.0 P ED and the new 45mm f/2.8 P.

They allow Matrix metering and I believe the addition of all the automatic exposure modes on AF cameras.

Again, these are manual focus lenses that are unique in their ability to take advantage of exposure and metering modes usually reserved only for AF lenses on AF cameras. You still have to focus them by hand.

AI-P are not D.

Nikon also, until about 1970, used letters on the front of a lens to delineate how many elements it had. The "P" stood for the Greek Penta, or five, elements. "Q" was quad (four) and etc.

Some people kludge older lenses to imitate P lenses by chipping them.

AF-n (AF-new cosmetics): 1990 top

This is just a way to distinguish between older and newer versions of some of the earliest AF lenses.

The very first AF lenses of the mid-1980s had thin, hard manual focus rings that everyone hated. Nikon presumed no one would ever touch them, so why bother to make them big and grippable when that would just make them get in the way when the AF motor rotated them?

It turned out that photographers preferred conventional wide, rubberized focus rings.

Therefore AF-n was often used to delineate the difference between an earlier lens with no real manual focus ring (AF) and a version from the late 1980s with a rubber focus ring that felt like one from a manual focus lens (AF-n).

Even though all of today's AF lenses are certainly newer than the AF-n from the late 1980s, the designation isn't used, unless a major redesign happens. I think the only AF-D lens that has been updated recently is the 28mm f/2.8D AF, which around 1998 was updated from the original old Series E design of 5 elements to a modern 6 element design.

AF-D, "D Type" (Distance Information): 1992 top

Another very subtle improvement you may safely ignore.

These lenses let the camera know the distance at which the lens is focused.

In very rare instances it helps the matrix meter, especially with flash, determine the exposure more accurately.

The biggest difference with D lenses is using flash and with subjects occupying only a small part of the frame. The distance information lets the newest cameras get the correct flash exposure, while with non-D lenses the camera has to guess harder.

AF-D work the same as AF lenses, even in difficult flash situations. The only difference I could see was if I had a backlit shot with an object in the foreground. If you focus on the foreground the image attempts to expose the flash for the foreground object, and if you focus on the background, the foreground object becomes too light

Another improvement is if you want to photograph straight into mirrors. Without a D lens you'll get underexposure because the image of the flash in the mirror fools the meter into underexposure. With D lenses you'll get a properly exposed image of a bright flash. I've expended film on this foolishness so you don't have to.

If you are buying used lenses on a budget you can get the earlier non-D versions cheaper. Don't worry here.

In fact, the instruction manual of the 105mm f/2.8D AF Micro-Nikkor cautions that the D feature of the lens can lead to the WRONG EXPOSURE unless you keep your flashes at the same distance from the subject as the film, which is a real obstacle to creativity.

There are a couple of ways to signify a "D" lens: Nikon usually marks its lenses as "50mm f/1.4D AF" as opposed to "50mm f/1.4 AF-D," but it all means the same thing.

Most AF-D lenses are AF and AI-s, and work great on manual focus cameras. You'll need to have a coupling prong added for use with the meter on ancient pre-AI cameras.

The D feature has no direct relation to autofocus speed, however as Nikon introduced newer D versions of existing lenses they sometimes sped up the autofocus speed, too. The Nikon 70-210mm f/4-5.6 is an example of this; the D version focuses several times faster than the earlier one. The speed comes from a change in mechanical gearing inside the lens; not the D feature itself.

Focusing speed has nothing to do with whether or not a lens is D. Of course newer lenses are D and newer lenses tend to focus more quickly, but the focus speed is determined by the gearing between the AF coupler and the focus ring, not the D feature alone.

All the newest AF lenses, even AF-S and especially G, are also D. Nikon doesn't bother to mark it anymore.

AF-I (AF-Internal Motor): 1992 top

These add an internal motor to focus the lens. There is no mechanical AF connection between camera and lens, it's done electronically.

Nikon introduced these in their super-telephotos in the early 1990s, which is the only sort of lenses you'll find as AF-I.

All Canon AF lenses have been this way, even the cheap ones, all along.

Not all Nikon AF cameras can autofocus with these lenses, make sure to investigate if you are buying an AF-I lens. AF-I lenses are usually $10,000 super-teles, so Nikon rightfully didn't go to the expense of adding this ability to the low-end cameras that would not be likely to be used with these lenses. In other words, why add $10 to the cost of every N60 when none of them would likely to be used on a 600mm f/4?

AF-I introduced a sloppy A/M, or automatic switching between AF and manual focus operation. It's a kludge; you have to keep your finger on the AF button (usually the shutter on the camera) while you grab the focus ring and it does eventually klunk over to manual focus. Nice try, but still years behind Canon's system introduced years ago. Nikon's AF-S lenses are much better this way.

The 300/2.8 and 600/4 AF-I lenses are not very fast. They sort of grind while focusing. The 400/2.8 AF-I is newer and much better. The 400/2.8 AF-I motor is super fast and very quiet, with just a hint of a very high-pitched whine that sounds like an AF-S lens. The 400/2.8 AF-I is as fast as the AF-S version, but the A/M switching is still primitive.

AF-I lenses usually offer several very nice focus hold buttons on the lens itself. The AF-I lenses are built like the tanks you should expect, unlike the plasticy AF-S lenses.

All AF-I lenses are AF and AI-s, and probably AF-D. They work great on manual focus cameras, too, giving you all features. You may need to have a coupling prong installed for pre-AI cameras.

I have measured that AF-I lenses draw the same amount of battery power from an F100 as do ordinary AF lenses.

Chipped Lenses: 1990s top

Nikon's best AF cameras have always worked with manual focus lenses. The autofocus F4 of 1988 gave full matrix metering automatically, and other cameras like the F5, F100 and N90 worked, but only with basic metering. (See Nikon Lens Compatibility for exactly what works with what.)

Again, since 2004, Nikon's better digital and film cameras now work great with manual focus lenses. The best ones, like the D3X, D300, D700, D3, F6, D200 and D3, give full EXIF data and color matrix metering if you'll go into a menu and enter the lens' focal length and maximum aperture. If you do this, they work great in manual and A exposure modes, but not Program or S modes.

Cheaper and older AF film and digital cameras wouldn't meter at all with manual focus lenses. They required the electronics of the newer AF lenses for this.

Enterprising Americans realized that if we add electronic CPU contacts to a manual focus lens, that Nikon's cheaper cameras will then have all the data they need to give all the usual metering and exposure modes, even with old manual lenses!

Legacy2Digital.com can add a chip to your manual-focus Nikon lenses so they give full matrix metering and Program, Shutter, Aperture and manual exposure modes on all Nikons, including the cheapest digitals.

AF-S (AF-Silent Wave Motor): 1998 top

These, and the AF-I, are the only lenses that autofocus on the Nikon D40.

These lenses have magical motors built into them to focus. The main advantage is not speed, but that most of these lenses allow one to grab the focus ring and turn it even in the AF mode to get instant manual focusing, without having to mess with any switches.

The AF-S motor is driven by the electronics of your camera. All Nikon digital SLRs work with them. Some of the oldest crappier film cameras can't autofocus with these. All the pro film cameras from the f4 (1988 on) work great with them.

AF-S first came out only on Nikon's $1,500 lenses, and today AF-S can be found on $99 kit lenses.

All AF-S lenses are AF-D. They still work great on manual focus cameras, too, unless they are G. The S in AF-S has nothing to do with the s in AI-s. You may need to have a coupling prong installed for metering on pre-AI cameras. Watch it, AF-S G series lenses are not AI-s and will not work on manual cameras.

I have measured the power drain from the F100 camera to focus these lenses. They take the same power that conventional Nikon AF lenses do.

The cheapest AF-S lenses, like the 18-55mm II, don't allow instant manual focus override. Most other AF-s lenses do.

G (Gelded): 2000 (won't work on manual focus cameras) top

G is not a feature, G is a handicap. G stands for gelded.

G lenses are lenses which have been crippled by removing their aperture rings to save cost. This is a classic example of taking away features while making customers think they are getting something new. G eliminates many features with older cameras.

These newest AF lenses have no aperture ring. This means that they will not work on manual focus cameras since there is no way to set the aperture. You can mount them, however every shot will be made at the smallest aperture and your metering will be way off (probably about SIX stops underexposed) since the camera has no way to know what the aperture will be.

This is silly, but you may get them to work on closed-loop auto exposure cameras like the FA in A mode. Good luck if you want to waste your time on this.

The G series work fine on all current AF Nikon cameras on which the manual aperture rings were a pain. On legacy AF cameras like the 8008 and 6006 you may lose the A and M modes, you'll have to see. I forget if for those modes if one sets the aperture on the camera or on the lens aperture rings.

All the G series are also D. They are not AI-s.

This removal of the aperture ring is typical migration for Nikon: Nikon tends to make new lenses work on all cameras for about 15-20 years after they discontinue the camera. AF cameras have not needed aperture rings for most modes since they were created about 20 years ago! Of course collectors growl about this and the brilliant new G lenses won't work at all on the brilliant FM-3a, but so what; all the other manual and AF lenses made today still work great on every camera they've made since 1977, and with a small modification to add an aperture prong will work great (with all meter coupling) even on the original Nikon F from 1959. This is good, although G lenses are still useless on manual focus cameras.

For an AF camera to control the aperture on any non-G lens with an aperture ring you just turn the aperture ring to the minimum setting in orange (usually f/22) and flick the lock so it stays there, and then everything is done on the camera body. If for some reason the lens is set otherwise the camera will flash something like " F - - " to let you know to set the lens back to the minimum setting.

PC-E (Electronic Diaphragm): 2008 top

Nikon finally decided to do what Canon did back in the 1980s, and adopt electronic diaphragm control for Nikon's newest PC lenses, the 24mm PC-E, 45mm PC-E and 85mm PC-E.

As of 2008, these diaphragms only work correctly on the D300, D700 and D3. On cameras which can focus an AF-S lens you get manual operation, and on other cameras, the diaphragm doesn't work at all. See PC-E compatibility.

Optical Innovations top

Micro (Macro): 1956 top

This simply is Nikon's designation for their macro lenses. The manual focus micro lenses focus up to half life size. The AF micro lenses focus all the way up to life size.

The effective aperture changes on all AF and MF micro lenses as the magnification is varied. This requires exposure compensation if used with an external meter in some cases. See variable aperture lenses below for details.

Reflex (Mirror) Lenses: 1961 top

Yip, these are telephoto lenses that do it with mirrors! They are designed based on the same principle developed by the Russian optical genius Maksutov and used in huge telescopes for astronomy.

They have a clear front. They have a big mirror in the back. They also have a little mirror on the back of the clear front element. Light comes in and bounces off the big rear mirror and is directed towards the little mirror on the front element. From there the light is bounced back to the film through a hole in the big rear mirror. This helps keep down the size.

These are not very good for photography, but they are very compact, light, focus close and are inexpensive. They do make great telescopes when used with the Lens Scope Converter since they do have great definition in their centers and little chromatic aberration.

They are poor for photography because they tend to:

1.) Have low contrast
2.) Have uneven illumination. They tend to have a hot spot in the center of the image and get very dim at the sides
3.) Are slow. Even though they have an f/ of about 5.6, because of the limited transmission and the mirror in the center blocking some of the light, they are really about one stop slower than marked. This makes them too slow to allow the fast shutter speeds that their high magnification demands
4.) Are too light. They are so light that they are extremely sensitive to any sort of vibration. Oddly enough, they work better handheld than on a tripod because you can couple your body mass to the system to damp the vibration.
5.) Have no diaphragm. It is difficult to focus because it is so slow, and then there is no added depth of field to help you out because there is no stopping down.
6.) Have awful Bokeh. The out-of focus highlights are very distracting donuts of light.

Variable Aperture Zoom and Micro lenses: 1961 top

If a zoom lens lists a range of apertures, for instance a 70-210mm f/4-5.6 lens, then the maximum aperture varies continuously as you zoom. This is done to reduce size, weight and cost. Fixed-aperture zoom lenses are heavier and cost more to make.

The effective aperture of the Micro lenses also vary as you focus closely and change magnification.

On AF cameras the computer figures all these changing f/stops by magic as you zoom. Whatever the camera says is automatically set correctly on the lens, regardless of zoom or macro setting. This causes no problem except that you can't get some larger apertures at some lens settings.

On manual focus cameras using external meters you have to guess at the actual aperture when you are in the middle of the zoom range or at close distances with the micro lenses.

There are two colored index marks from which you read the f/stop on a variable zoom. The colors are coded to the colors of the focal length markings. You have to guess when in between the ends of the zoom range.

On Micro lenses the exposure compensation values for different magnifications are listed in your manual. I prefer to tape scales onto my lenses instead (see 55/2.8 micro review for a picture of these scales)

This is unimportant due to TTL metering if you are using the camera's meter or TTL flash.

If you are using a manual focus camera with an external meter or the A mode of a flash then you need to pay attention. The AF cameras correct automatically, the MF cameras do not.

CRC (Close Range Correction): 1967 top

"Close Range Correction," means the lens optimizes itself as the distance changes. This is done with "floating elements" that move in relationship to others during focusing. This is most needed on macro and fast wide-angle lenses like the 35mm f/1.4 AI-s and 105mm F/2.8 AF-D Micro. The benefit to this is that it allows wide-angle and macro lenses to focus closer than they could otherwise while retaining great sharpness.

Nikon talks about this here.

For instance, the 35mm f/1.4 AI-s has CRC, while the 35mm f/2 AF-D does not. The AF version focuses very close, but does not have the sharpness at close distances, especially in the corners, that the older manual focus lens does. The AF lens is better in just about every other way, though.

You can see this working in the lens if you are observant. In a CRC lens some of the elements rotate when focusing while others do not. For instance, most of the AI-s wide angle lenses have CRC and rotate the front elements while the rear ones do not, even though all the elements are moving forward and back while focused. The reason some rotate and others don't is that some run on another set of helical threads while others run on the main set. In this way the spacing between groups varies as intended by the lens designer.

Fig. 4.) This is the 28mm f/2.8 AI-s lens. It is focused at infinity. Fig. 5.) Focused at 0.2m.

Note how the front element retracts slightly from the rest of the lens. In this lens the front elements rotate while focusing, while the rear ones do not.

Nikon does not mark lenses that have CRC. You have to read the sales literature or look for yourself.

PC (Perspective Control): 1968 top

These are lenses with mechanical adjustments mimicking the movements of view cameras.

They are called TS, tilt-shift, by Canon.

They can keep parallel lines parallel in buildings or groups of trees while looking up or down. They also can exaggerate perspective. Without these lenses, parallel lines will converge if the camera isn't perfectly level.

PC lenses are a pain. They provide only limited manual metering, manual focus and usually require a tripod.

Nikon has made a 35mm f/2.8 PC, followed by the 28mm f/2.8 PC, for decades. Each of these provides vertical and horizontal shifts, but no tilts.

Nikon's 85mm f/2.8 PC provides tilts, to allow enormous depth-of-field.

I sold my 35mm PC lens a decade ago. Photoshop provides much faster correction of converging lines. Today I use the Photoshop's Lens Distortion Filter for that, in one mouse movement!

Aspherical Elements: 1968 top

All conventional lenses are spherical, meaning that all the curved surfaces are the same shape as a part of a sphere. Even if the lens is cut into an odd shape as eyeglasses are, the curvature of the optical surface is still spherical.

Spherical surfaces are used because that's what's easy to grind. To make any shape other than flat or spherical requires very expensive custom manufacturing procedures.

Spherical surfaces are not the optimum shape for lenses. In fact, "spherical aberration" is the phrase used to describe a lens defect that results when one only uses a single spherical element.

The ideal shape is a curve, but not a spherical one. One of the reasons lenses require many elements is to attempt to simulate the ideal curvature with the clever use of many easy-to-manufacture spherical surfaces.

There are several ways to make aspherical lens elements:

Precision Ground

The best and most expensive way is to grind each one carefully by hand. Nikon calls these "precision ground" and are found in very expensive and superb lenses like the 28mm f/1.4 AF-D, 58mm f/1.2 NOCT and 20-35mm f/2.8 AF-D.

Molding

There are several more economical ways to make aspherical elements. They don't perform quite as well as the hand-ground ones, but for a price affordable by casual amateurs they can offer performance improvements for the same price as conventional spherical lenses.

Molded Plastic

One of these ways is to just mold an aspherical element out of plastic. This is often used to correct distortion in point-and-shoot camera viewfinders.

Molded Glass

Another less expensive way is to mold the glass elements in bulk instead of grinding each one individually. In this way the expense is in making the mold once, and then the elements are stamped out cheaply. This allows increased, but not spectacular, performance at a reasonable price for high-volume lenses. Nikon uses this process in the 18mm f/2.8 AF-D, 28-200mm f/3.5-5.6 AF-D and 24-120mm f/3.5-5.6 AF-D. The 28-200 also uses hybrid aspherical elements.

Hybrid

Another clever way is to glue a thin molded piece of aspherical plastic to a conventional glass element. This gives the advantage of adding mechanical stability to the plastic element since it's glued to a glass substrate. This is also inexpensive and allows some performance improvement at the same time. Nikon uses this in the 28-70mm f/3.5-4.5 AF-D, 35-105mm f/3.5-4.5 AF-D and 28-200mm f/3.5-5.6 AF-D. The 28-200 also uses molded aspherical elements.

NIC (Nikon Integrated Coating): 1970 top
SIC (Nikon Super-integrated Coating) top

Nikon was among the first to introduce multicoating in 35mm camera lenses with the 1970 release of the 35mm f/1.4 lens. True to the good old days of Nikon, they just did it because it made for a better lens, even though it was not very obvious to the casual observer or at the sales counter. I don't think Nikon promoted it much, if at all.

Just about every Nikon and other brands of lenses today are multicoated. No one worries about it anymore. Every Nikon lens that needs it has it. This is standard today and it rarely is mentioned, except for very cheap lenses that claim "multicoated" and may only have one surface multicoated just to try to claim it.

Multicoating not only allows a reduction of lens flare and ghosting, but also increases light transmission. It becomes difficult to design decent lenses with many groups of elements without multicoating. This is because with many groups of elements, as we find in most zoom lenses, the light can start getting lost and bounced around inside the lens without decent coatings.

Multicoating also allows careful fine-tuning of a lens' color rendition. Lenses can impart slight color casts to the light that passes through them. Even if lenses seem to look neutral to our eyes, vivid color films like Velvia actually amplify color differences. Carefully designed multicoating allows the lens designer to achieve the color balance he prefers.

You can look into your lens to see what sort of coating it has if you are really that curious.

Look into your lens. Look carefully at the reflections in the glass.

An uncoated lens, only found on disposable cameras today and cameras made before W.W.II, will show bright white reflected images. You will recognize these reflections as identical to those you see in windows and in most people's eyeglasses.

A single-coated lens has reflections that are usually tinted magenta, blue or amber.

A multicoated lens surface will take on many other colors. Most often you will see green, but every other color may also be seen, like deep red. The whole point of multicoating is to eliminate these reflections, so they may be very dim. If you see a myriad of colors reflected from the different elements you have a multicoated lens.

Each lens surface may have different sorts of coatings. Some filters are coated on only one side just so they can be sold claiming "coated filter," just as some discount lenses may have only one multicoated surface so they can claim "multicoated."

Unless you are scraping the bottom of the discount barrel don't worry about this with modern lenses. They all are coated however they need to be coated.

Here are what the coatings in some Nikon lenses look like. The magenta color doesn't imply multicoating (even though it may be), but the green reflections do signify multicoating.

Fig. 8.) 600mm f/5.6 AI-s, green coating. Fig 9.) AF 20mm f/2.8, green coating

Fig. 10.) 200mm f/4 AI, green and red coating. Fig. 11.) AF 28mm f/1.4D, green and blue coating.

Fig. 12.) AF 28-85mm, green coating. Fig. 13.) 85mm f/2 AI-s, green coating

ED (Extra-low Dispersion) Glass: 1975 top

"Extra-low Dispersion glass." Nikon started using this only in their super speed super teles in the late 1960s. These lenses say "ED" on and have a gold band around the barrel. All ED lenses say so.

Since only the most expensive lenses used or needed this glass it acquired a cachet. Therefore Nikon started using the moniker on cheaper lenses, and today it seems everything says ED on it. Short and normal lenses have no need of this glass; it's benefit is reducing secondary chromatic aberration, which is green/magenta color fringes that used to plague lenses of 300mm and up.

ED glass is an improvement over the fluorite used by other makers at the time because it is hard enough to use for outside elements, unlike the soft fluorite.

ED glass helps eliminate secondary chromatic aberration (green-magenta color fringes) which is what previously prevented the design of practical super speed, super sharp super teles.

Discount brands now purport to use this glass. Ignore all these claims; they may or may not use this glass, but there are far more important factors in lens design than just what sort of glass was used. See the reviews for specific performance tests.

ED glass is less stable with temperature than conventional glass, and so the focal lengths of these lenses change slightly with temperature. Therefore there is no hard infinity focus stop on ED lenses because the point of infinity focus will change a bit with extremes of temperature.

ED glass also has a lower index of refraction so it requires more deeply curved elements for the same focal length.

The whole point of owning a Nikon is to use these super tele lenses, so don't be a bone head and waste your time with non-Nikon super telephoto lenses. You will find that when you go to sell a Nikon super telephoto that you will sell it for what you paid for it, so it's sort of free. If you have a discount lens (Tokina, Tamron, Spooginar, Sigma, etc.) you will have to sell it for far less than you paid, so the discount lenses actually cost MORE to own.

IF (Internal Focusing): 1976 top

"Internal Focusing." In the old days, the entire lens had to move in and out to focus. Telephoto lenses had to be designed with huge focusing tracks just to let them focus at all, and they couldn't focus very close because the helicoids just weren't long enough. The long focal lengths meant that there were long distances the lens had to move to focus.

Nikon discovered that one could focus the lens by just moving some elements around inside the lens barrel.

IF lenses focus closer and faster than conventional telephoto lenses. IF was a fantastic innovation for telephoto lenses when Nikon invented it in the 1970s for the manual-focus super teles. Today, most modern AF zooms, super teles and some macro lenses use this technique. It helps AF lenses focus quickly because there is less glass to have to move around.

The optical trick is that the internal elements move slightly to shorten the lens' actual focal length as one focuses closer. This lets these lenses focus very close. It also means that when compared to a traditional lenses that the IF lens will appear to have a slightly shorter focal length than marked at close distances. This discrepancy disappears at infinity.

RF (Rear Focusing): 1988 top

"Rear Focusing." Same as IF, except just the rear element or group moves.

Fig. 6.) AF 28mm f/1.4 lens focused at infinity. Fig. 7.) Focused at 0.35m.

The rear element retracts as the lens is focused closer.

DC (Defocus Control or variable bokeh): 1990 top

These lenses are NOT soft focus lenses. They are super sharp.

They are for advanced users who want to make very subtle variations in the appearance of the out-of-focus areas. The adjustment does not affect the in-focus part of the image.

This baffles most people; the effect is very subtle and only affects the out-of-focus areas.

These lenses do this by varying the nature of the correction of spherical aberration. This allows adjusting the bokeh, or appearance of the out-of-focus areas of the image.

See the bokeh for more explanation.

Yes, these lenses are superb for portraiture. You need still need to provide any soft-focus or diffusion effects by putting things in front of the lens, since they are incredibly sharp at the in-focus areas.

VR (Vibration Reduction): 2000 top

This is the same as Canon's IS Image Stabilization. It stabilizes lens and hand vibration to avoid the need for a tripod.

It is a very helpful feature for shooting handheld in dim light, as I often do. I love it. It doesn't cure all or every shot. It greatly increases the percentage of sharp shots you get at longer shutter speeds handheld.

It doesn't stop action. It's not for sports, although it does help smooth out slow pans.

It saves you from having to carry a tripod, a huge help. If you use a tripod remember to turn it OFF, since if you leave it on while on a tripod it will blur your image!

I'm addicted to VR. See Why VR Matters.

DX: 2003 top

These lenses have small image circles which only can cover the smaller DX (16x24mm) frame.

See Nikon DX Lenses and Crop Factor.

Nano Crystal Coating: 2006 top

This is a magical new anti-reflection coating which surpasses the multi-layer coating that's been popular since 1970. Nano Crystal coating was invented by Nikon's semiconductor manufacturing division. It uses a layer of zillions of sub-microscopic particles just 10-20 nm (smaller than the wavelengths of light itself) to bend light rays gradually into the glass. This prevents them from bouncing off at a hard angles as they do ordinarily.

The particles are packed with air between them so the effective index of refraction is less than the index of the particles themselves. They are packed more closely closer to the glass, so that their index of refraction varies gradually. Therefore these coatings are effective regardless of the angle of incidence, and more effective across a broad range of wavelengths because they are not working on the principle of interference and fractions of wavelengths.

As of 2007, Nikon's camera lenses have only one internal surface with this coating. It's just another letter for Nikon to use to push new lenses on people. It means nothing to photographers all by itself.

A lens' ghost, flare and contrast performance depend on many, many many factors. It depends more on the wisdom of the lens designer than a coating on one surface of one element. The other zillion surfaces have Nikon's traditionally excellent Super Integrated Multicoating (SIC).

Nano Crystal coat is, and will be, especially effective on the inside surface of the first element of ultra-wide and fisheye lenses, because it is this surface which begets most ghosts in these lenses. The nano-crystal coating is especially effective here because it is effective regardless of the angle of incidence.

Traditional coatings have a very hard time in ultrawide lenses because they 1.) depend on their layers' thicknesses being related directly to the wavelengths, and therefore incident angles, of light, and 2.) the ghosts in these lenses happen because light comes in from the top, is strongly bent by the front element, hits the inside surface of the strongly curved front element on the bottom at some weird angle. These weird angles lead to a lot of ghosts in ultrawide lenses, and traditional coatings are ineffective at these angles.

I wish Nikon offered a retrofit to nano-crystal coat this particular surface in older lenses that need it, like the 15mm f/3.5 AI-s.

More information on Nano Crystal coat from Nikon in Japan: General Information and Technical explanation.

Joe Photography

Sunday, January 9, 2011

Nikon Lens Technology

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