The Nikkor-O 55mm, f/1.2 CRT Oscilloscope
The Nikkor “O” (for oscilloscope) or CRT-Nikkor, as it is called is perhaps the most “different” lens that l own. This lens was made for monitoring CRTs and has trouble with daylight, which is part of its charm, since all kinds of wonderful color variations can be expected. This is not an APO lens or anything close to it because it has been corrected to render phosphorus colors, and is said to be optimum at f/4 and f/5.6.
The CRT or Oscilloscope Nikkor first appeared in the mid-1960s as an industrial lens designed for photographing oscilloscope displays and cathode-ray tubes, thus the nickname (CRT Nikkor). It was designed with a fixed focus and has no helicoid or focusing ring. However, it is very fast, with an aperture of f/1.2 wide-open. The maximum sharpness is said to be f/4. As mentioned, the lens is very, very sharp. It is listed as having f/1.2, but keep in mind that all ratings are for a lens at infinity, and this lens is designed for close-up range, so the f/stop would be more like f/1.4.
Even, so the lens is about as sharp as anyone could want. As for bokeh, the CRT-Nikkor is over the top, bokeh on LSD, which I particularly love. The CRT Nikkor can help you get out of the box to become more creative. At least that has been my experience.
This lens is not designed to be mounted on a standard Nikon DSLR, but rather uses the Leica M39 thread mount. The M39-to-Nikon F-mount adapters can be readily found on Ebay. Many people prefer to use an M39-to-T2, and then a T2-to-Nikon-F-mount adapter to mount the lens on a DSLR. This works well for images and close-up work less than 1:1. For macro work above 1:1, use a 52mm reversing ring. There are two versions, the first released in 1964, with the only difference being that the second version is marked (red engraving) “M=1/5.”
As pointed out, this was a lens built to photograph computer monitors, CRTs, the old ones with a curved face. The lens also has a corresponding curve, and so this is anything but a flat copy lens. In this way, it distinguishes itself from almost all other industrial lenses. At f/1.2 it is fast and allows plenty of light in the viewfinder, which is great for old eyes. It has a narrow depth of field at its sharpest and I consider it a specialty lens, although the specialty is very desirable, that of allowing for sharp resolution in parts of the frame, but a Zen-like blur instead of standard bokeh, that, and the ability to make whole areas of color just go wild, well beyond a gradual decline.
As mentioned earlier, there is no focusing ring, but there is an aperture ring with 12 blades. The scalloped aperture ring as stops: 1.2, 1.4, 2, 2.8, 4, 5.6, 8, and 11, all measured at infinity. The lens components were designed for handling particular phosphorus colors, I am told.
The CRT Nikkor can be used either on a DSLR (and focus rail) or attached to a bellows. The lens is made for 1:5, which means that even with the smallest adapter-extension, perhaps you can only reach something like 1:4. I use it on a focus rail.
If you a looking for an all-around lens, this is not it. As mentioned, this is a specialized lens, with all kinds of flaws. The contrast is average, and there is definitely lateral chromatic aberration a-plenty, and even some amount of longitudinal chromatic aberration. Since I usually only use APO lenses, why have one?
I love this lens because it forces me out-of-the-box despite myself. It is like a lens on an acid trip. The lens is very sharp when used correctly. As for myself, I tend to use it fairly wide open to record razor-thin depth-of-field, and I stack that depth of field (with many layers) to put the part of the image I want accented in high focus. Then, I let the rest of the image go wild with flare and bokeh. I happen to like that effect, but some don’t.
Perhaps the reason I like it is that it combines that part in me that wants to be exact, even scientific, with another part of me that has glimpses that this life we live is very ephemeral, like a dream we are having. So the flaring, surprise colors, and crazy bokeh represent the dreamer (and meditator) in me – something like that. Call it the Zen in me.
The lens has a long, Leica-mount thread (39mm) and comes with a jam nut. They turn up on Ebay fairly regularly for between $600-$1100 (2015).
In summary, with the CRT Nikkor, wide open (and fast), I can layer just the tip-of-the-top of some object, pushing that into focus. Then I contrast this with the rest of the image with is all bokeh -- out of focus. At least for me, this lens can be very much hit or miss, meaning that sometimes the results are miraculous, while at other times, only too average. In other words, this is lens is a little bit difficult to predict or control. With a little care, predictable (and desirable) results can be expected.
There is probably more I could say, but I will let the images do the talking. Here is a sample of what I have done with this lens. I hope you enjoy them. However, the lens is so flexible that of course you will develop your own style.
Focal Length: 54.3 mm
Widest Aperture: f/1.2
Narrowest Aperture: f/11
Aperture Blades: 12
Filter Size: 52mm
Hood: None standard
Close Focus Distance: 417.1mm overall working distance
Reproduction Ratio: 1/5x
Weight: 385g
Color: Not corrected, 0% vignetting, 1.14% distortion
Rear Mount: M39
Resolution: 250 lines/mm
Image Area: 24x36
Standard wavelength: 400 - 650 milli-micron
Construction: 8 elements, 6 groups
Standard Magnification: 1/5.5X – 1/4X
Sharpest at f/4
Chromatic Aberation: Mild at center, more severe in the corners.
Axial CA: Some on out-of-focus details.
