The final touch.

In earlier pieces dealing with the installation of a CPU in old Manual Focus Nikkors, I have explained most of the benefits of CPU use. Further, by making tailored lens profiles, I have made it possible to get the best possible results as regards freedom from vignetting, distortion and chromatic aberration.

The last frontier is optimal focus.

When using MF lenses on the D700, which is blessed with a large, bright finder and an LED confirmation dot, with arrows showing which way to turn the lens when it’s not in focus, things are pretty easy. The LED is fairly accurate and the addition of a magnifying eyepiece further simplifies regular old screen focus, if the dot is not to your liking.

However, get in really close at f/1.4 with something like the Nikkor-S 50mm, f/1.4 and any errors start to show themselves.

To check things out, I placed the camera on a tripod with a QR head (to permit accurate replacement) at a roughly 45 degree angle to a bookcase and four feet distant. Not surprisingly, the contents are solely photography books! One snap was made with the single center focus rectangle placed on the ‘O’ in ‘HORST’.

I then loaded the image in LR4 and looked at the enlarged version to see what was what.

Well, the LED dot was wrong. I have marked the focus point and the point of sharpest focus on the image below.

Red line is where the LED dot focus was made. Green dotted line shows where the image is sharpest.

The sharpest focus is closer to the camera than the point at which focus was aimed.

The CPU installed in the lens permits adjustment of the point at which the LED illuminates. You can move that point back or forward in 8 discrete steps in either direction, making a total of 17 settings including the default. The provided instructions use English poorly and it’s hard to divine which way to go.

Here’s the rule. After doing the 1-6-1 second programming setup:

• If you hit the shutter release when the top LED panel indicates F10, the LED will illuminate at a shorter focus point distance from the camera as indicated on the lens, meaning further from infinity.
• If you hit the shutter release when the LED panel indicates F20, the LED will illuminate at a longer focus distance from the camera as indicated on the lens, meaning closer to infinity.
• Each subsequent shutter release at F10 or F20 will move the LED illumination point further in the respective direction.

Now the LED is not that sensitive. In practice there’s a small range (“more or less right”) where it stays illuminated and I simply oscillate the lens’s focus collar either side until I am centered on the focus range for the LED illumination point.

In the above example the LED was illuminating on a point too far from the camera as optimal focus was closer than the point at which the LED was aimed. Thus I needed to move the LED illumination point away from the camera, meaning that I operated the F20 switch in the programming instructions once.

I then refocused the lens on the ‘O’ in ‘HORST’ and took a second picture. Here is the result:

Red line is where the LED dot focus was made. Green dotted line shows where the image is sharpest.

Bingo! Bang on. The LED illumination and best focus point are identical.

Just to confirm, I then cycled the F20 one more time, moving the LED illumination point yet further away from the camera, with the focus collar set closer too infinity to illuminate the LED at the same point in the identically framed image.

Red line is where the LED dot focus was made. Green dotted line shows where the image is sharpest.

In the above example the LED was illuminating on a point too close to the camera as optimal focus was closer than the point at which the LED was aimed.

So I went through one F10 cycle to revert the optimal LED illumination point, as in the second picture above.

In practice, it’s really only necessary to do this with wide aperture lenses used at close distances, or extremely long focus lenses which have very shallow depth of field, like the 500mm Reflex Nikkor. In these circumstances, you must remember to do your critical focusing using the LED light not the focusing screen if you have found it necessary to move the LED illumination point using CPU programming.

But this absolutely puts the icing on the cake for fast and/or long MF Nikkors. For AF Nikkors (AF D or AF-S) a like functionality exists in the body of the camera in the rear LCD menus. With AF Nikkors the camera ‘remembers’ the setting for each lens; with MF + CPU lenses, each lens stores its own setting in the glued-on CPU. This does not address the case where the photographer wants to use the same MF + CPU lens on different Nikon (or Fuji) bodies. In that case, if the bodies differ significantly, it’s best to have the factory fix the body rather than trying to fix the lens.

I have only found it necessary to move the focus point on three lenses – the 50/1.4, the 85/1.8 and the 105/4 Micro – of the dozen I own. All the others are spot on including the 500mm f/8 Reflex! Why these two lenses should differ, I do not know, but differ they do, as multiple tests have consistently confirmed. Indeed, I only really started to see what the 105/4 Micro-Nikkor could do after this focus fine tuning process. It is ‘scary sharp’!

Is this all worth the effort? If you use the lens at f/1.4 or f/2, just check this out.

By the way, to learn more about Horst, one of the greatest fashion photographers of the twentieth century, click here.

A standout classic.

The 50mm Nikkor-S f/1.4. One of the most beautiful optical masterpieces yet conceived.

Where Leitz’s contemporary chromed Summilux is all about elegance and grace when it comes to looks, the Nikkor-S boasts an unrestrained machismo. Clearly, you could give someone a fair old whack with it then use the same blunt instrument to take their picture!

The 50mm Nikkor-S f/1.4 lens is an affordable classic. Mine ran me $144 in near-mint condition, plus $25 for Ai conversion by John White, and $30 for a CPU. The lens is abundantly available in just about any condition on the used market. Given its low price, it’s false economy to buy a beater. This 50mm pre-Ai lens was made between March 1962 and June 1974, with the last batch, made in 1973-74, marked ‘S.C’ denoting multi-coating. The first S.C ones were in an all metal barrel, the last adopted the awful plastic covered version. Thereafter, the formulation changed from 7 elements in 5 groups to 7/6, and Ai and Ai-S versions came along. Mine is a single-coated 1971 example. As is the case with all pre-Ai Nikkors, construction quality is simply unrivaled. Fit, finish, materials, engraving and cosmetics are all top notch.

The front element is large, and though somewhat recessed, the lens gains from a lens hood, especially with the earlier single-coated versions. I have a period Nikon HS-9 hood on mine. Filters are Nikon’s standard 52mm diameter

The lens shows some vignetting on full frame (none on APS-C) fully open which disappears completely by f/4. My lens correction profile fixes that and you can download it here. Such modest chromatic aberration as there is can be easily removed by making sure the appropriate box is checked in your file import setup. Diffraction is very minor at f/16, with the highest resolution being delivered in the range f/2.8 through f/11. The seven sided aperture makes for attractive rendering of out-of-focus areas.

Performance at full aperture needs no excuse, and is fully usable, with resolution good enough for large prints right to the corners. By f/2.8 it’s as sharp as it gets.

CPU installation – not for the faint of heart:

Unless you are very comfortable with tinkering, CPU installation in this lens should be delegated to an expert. The rear baffle is 1.548″ in diameter, well in excess of the limit of 1.427″ which permits a straight glue-on of the CPU to the baffle. If you are doing the job, first mark the position of the CPU on the flange using a scribe or pin (“limit lines”). You need to remove the baffle metal in the location of the CPU. The baffle is set-off 0.03″ from the moving rear lens optical assembly and is 0.13″ thick. Thus, removing the baffle material reduces the effective diameter by 0.13″ from 1.548″ to 1.418″, (the 0.01″ clearance is retained) which is ideal for proper CPU clearance. I have found the range of 1.363″ through 1.427″ works fine, with play being taken up by the sprung contacts on the CPU.

To install a CPU you must first remove the baffle and flange as one assembly. Do not separate the baffle from the flange. Leave the two very small radial countersunk screws untouched. Of the five slotted screws retaining the chromed bayonet flange, remove four. Use a really tight-fitting, professional miniature screwdriver. I use, and recommend, the set which comes from Wiha. You want the screwdriver to be a really tight fit across the whole width of the slot in the screw. Anything less risks damage.
Do not remove the red circled screw, illustrated below.

Do not touch this screw. If you must, loosen it, but do not remove it.

If you look really hard, you will see that the slot in this one is shallower than in the other four. This screw retains the aperture return tensioning spring, and you must leave it intact. It is retained by a small threaded brass post on the inside of the flange. The post is accommodated by a recess in the inside of the lens. The related screw does not retain the bayonet flange to the body of the lens.

When you remove the flange you will see the spring mechanism where it is retained by this screw and also the attachment point of the other end of the spring on the aperture setting claw which slides around the periphery of the flange. The stop down lever is the only part of this claw assembly which protrudes through the flange.

The aperture claw on the inside of the flange. The spring returns the diaphragm to maximum aperture.

The spring retaining nut goes in the red orifice. The claw goes in the green one after
checking that it mates with the (chrome – barely visible) aperture tab inside the body of the lens.

With the flange removed I used a Dremel tool with a cut-off wheel to remove the flange in the location of the CPU.

They don’t make them like this any more:

When I had the rear bayonet flange off to do the machining for the CPU, I noted several fine abrasive stone touch up marks where the flange’s thickness and planeness had been adjusted manually as part of final assembly. This is what makes these so consistent and so good, and indicates a process of manual fine tuning on final assembly prohibited by modern skilled labor costs.

The cuts:

The arc of your longitudinal cuts is denoted by the previously marked scribed limit lines. The depth of the cut is such that the flange is removed to a point flush with the chromed body of the flange. When replacing the flange, you will see two circumferential cut-outs in the rear of the lens. The smaller one is for the post/screw/spring assembly. the longer of the two is for the aperture actuation claw attached to the flange. Look down the longer slot. You will see a small chrome tab. This is where you must insert the claw when replacing the flange. The claw will mate with the tab and restore aperture operation. If you do this wrong, and miss the chrome tab, your lens will remain stuck at full aperture. Guess how I know!

In the following picture I have shown the flange replaced on the lens to show the cut-out baffle material. Before replacing the flange screws, I checked that the aperture control worked properly.

The bayonet flange back in place after removing the arc of baffle metal.

With the flange tightened down again, I did a dry run with the CPU, installing it with two-sided sticky tape applied to the flat side of the CPU, not to the concave curved side. The concave side must clear the lens barrel which moves longitudinally as the lens is focused. With the sticky tape temporary installation, I inserted the lens in the D700 and did the usual CPU programming.

CPU in position using two-sided sticky tape, for testing fit and for programming.

Epoxy:

Permanent installation using two-part epoxy is next. The next precaution to take is to be absolutely certain that no epoxy glue squeeze-out from the CPU/flange mating surfaces makes its way onto the lens barrel. If it does, your lens will be trashed, as the lens barrel containing the optics will be glued to the flange and CPU. You will be unable to focus the lens. Accordingly, I took the simple precaution of interposing a piece of writing paper between the flange and lens barrel as shown below. I tucked this in as far as I could.

Paper insert protects the lens barrel from glue squeeze-out.
As you can see, I have removed the ugly external ‘claw’ on the
aperture ring (two small screws) which serves no purpose on the D700.

With the lens at infinity (to retract the barrel to the maximum and provide a reference for the radial positioning of the CPU), epoxy applied and the CPU in place and snugged up against the inserted piece of paper, I was unconcerned about glue squeeze-out between the inside of the CPU and the barrel with the optics. In fact I had some squeeze-out (on the second attempt – see ‘Be Careful!’ below) and the paper was seized when the epoxy cured. I simply removed the flange and pulled the paper off from the inside of the flange, leaving a nice glue squeeze out line shaped to fit – but not touch – the barrel. The clearance is thus one paper thickness. Not much, and certainly not a job for the nervous or cack-handed.

When replacing the flange, I first made sure that the holes in the flange aligned exactly with the threaded sockets. Then I took care to tighten the four retaining screws in a criss-cross pattern, in three stages of increasing tightness, to avoid any possibility of distorting the flange.

The result works perfectly and the CPU is well protected by virtue of its partial recess in the baffle.

Be careful!

So there I was, banging away merrily with the newly chipped lens, thinking all was right with the world, when I noticed the exposure data in the finder had suddenly gone badly awry. Instead of apertures I was getting whole numbers. I whipped the lens off and …. found the CPU merrily lying about in the well of the mirror box. It had come off! Well that does it, says I, no more Mr. Nice Guy, so I set to the son-of-a-gun with fresh epoxy and a woodworker’s clamp, after giving the mating surfaces a good scrubbing with a final wipe using isopropyl alcohol to remove all traces of grease.

The first time I glued the CPU I was careful not to get any glue squeeze-out between the inside of the CPU and the lens barrel. This time I decided to have some, reckoning that the protective paper, used while the epoxy was drying would prevent seizure. It did. Once dry, I removed the bayonet flange one last time and removed the protective paper from the inside of the CPU. The greater amount of epoxy and the squeeze-out line gives a stronger result.

No more Mr. Nice Guy.

This time it looks like it’s going to hold. I gave it a fair bashing about in the field, never babying it when changing lenses, and the CPU is still in place. I’m just counting my lucky stars that the mirror didn’t go smashing into it when it came off.

Lens correction profile:

You can download the profile here.

With aperture control passed to the lens, as is normal for pre-Ai-S optics, here are eight test snaps from f/1.4 through f/16. You can see the vignetting clearly in the first three at f/1.4, f/2 and f/2.8. Accordingly, the lens correction profile I have made contains four files – at f/1.4, f/2, f/2.8 and f/4. The f/4 profile is automatically applied from f/4 through f/16.

Eight test shots with CPU installed, ‘A’ exposure automation.
No lens correction profile was used here. Vignetting disappears by f/4.

Importing the same pictures, with the lens correction profile activated, completely eliminates corner vignetting at the three largest apertures:

Eight test shots with CPU installed, ‘A’ exposure automation.
With lens correction profile applied. No vignetting visible at any aperture.

Note the evenness of exposure over a range of eight apertures (using the automatic ‘A’ mode – aperture priority) with aperture settings controlled by the lens. Use of the lens correction profile makes an already great lens that much better.

In tomorrow’s article I will illustrate how to fine tune the illumination point of the viewfinder focus LED in the D700 (and other bodies) using programmable settings in the CPU. Nailing perfect focus at f/1.4 is key to extracting the very best results from this great lens. Those not needing f/1.4 should look to the 50mm f/2 Nikkor-H which is every bit as capable, smaller, lighter and much cheaper while permitting simple glue-on CPU installation.

Early snaps made using this lens are here and here, now that I have established that my CPU will not fall off again …. The 50mm f/1.4 is to Nikon what the 50mm Summicron f/2 is to the rangefinder Leica. A classic masterpiece of optical design and mechanical engineering which defines the marque. I expect my son to be using this one long after I’m six feet under, pushing up the daisies.

Neither here nor there.

Blue, blue, blue. The mottling is from a mesh screen on the window, not in the lens.

Before the DSLR revolution the standard ‘3 lens’ outfit for the 35mm SLR snapper was comprised of 35, 50 and 135mm lenses. Today, with super range zoom lenses that is all yesterday’s news. In between, that outfit got shorter and wider, many opting for 28 or even 24mm at the wide end, 35mm as the ‘standard’ lens with 85-105mm at the long end. It’s not that there was anything inherently wrong with the 135mm focal length, it’s just that it was too long for portraits and too short to be really, well, long. But before they fell out of favor, Pentax, Minolta, Canon and Nikon made a boat load of 135s.

If serial numbers are any guide, Nikon alone made over 300,000 of the early 135mm f/3.5 design, their ‘budget’ model, comprised of but four lenses in three groups and made during the period June 1959 through March 1977. The first ones coincided with the release of the single greatest 35mm SLR in the history of the design, the Nikon F. And, indeed, my 1971 version not only remains budget priced – $65 near mint – but also comes with that exceptional build quality common to all Nikkors of the era, regardless of price. The same quality found in that Nikon F of yore.

A few minutes with a screwdriver and a flat file saw me confer the appropriate Ai relief on the rear of the aperture ring, which comes off easily once the five bayonet flange retaining screws are removed. Those less confident in their mechanical skills should send the lens to John White along with the modest fee asked. You really will hate getting this wrong. Another few minutes and overnight to let the epoxy cure saw a CPU installed.

Note the wild blue color of the single anti-reflection coating on the front element, something common to lenses of the period. No matter the color, it works well, though the lens benefits from a lens hood when used into the sun. Modern optics with multi-coating are more flare resistant. Then again, they don’t come along at $65, either ….

Preliminary snaps indicate a near total absence of vignetting or distortion at any aperture, with outstanding resolution fully open, peaking at f/8. But then that is to be expected from a beautifully simple Zeiss/Leitz optical design which goes back to the 1930s.The laws of physics do their thing at apertures smaller than f/11, where diffraction messes with light rays, but the optic is superb and highly recommended. The rendering of the out of focus bits is especially noteworthy, smooth and gentle. Balance on the Nikon D700 is well nigh perfect – a solid body and a no less compromised lens.

Lens correction profile::

Though in this case it’s pretty much overkill, the lens is that good, you can download the lens correction profile here. Maximum definition is reached at f/4.5 and maintained down to f/16. Distortion is negligible.

Some snaps from this lovely lens are coming soon. Look here.