Leica Monochrom Typ 246 x PC-Nikkor 28mm f/3.5
People understand why tilt lenses exist – making super-expensive Canon DSLRs produce pictures that look like they were taken with a toy camera (or making the subjects themselves look like toys). No one knows, though, why shift lenses were once a thing. It’s all a matter of perspective.
The truth, from a certain point of view
Photography always has (and always will) present this problem: needing to fit a large object into a frame that is constrained by lens focal length. Conceivably, with a superwide lens you could, but then you end up with a lot of extra dead space in the frame. Which defeats the purpose of using large film or sensors.
If you want to get the whole thing in frame with the minimum number of steps or expenditure of time and money, your choices are to use a really wide-angle lens, tilt a camera with a more moderate wide-angle up, learn to fly. All of these are sub-optimal. First, the really wide-angle lens is great in that you can capture the top of the object without tilting the camera. The problem is that making an engaging photo with a wideangle is actually extremely difficult – because it tends to shrink everything. Depending on how the sun is, it also stands a better chance of capturing the photographer’s shadow. Second, tilting up a camera with a more moderate wide-angle lens “up” turns rectangular buildings into trapezoids, which works for some pictures but definitely not others. Finally, learning to fly is difficult. But watch enough Pink Floyd concert films, toke up with the ghost of Tom Petty, or study Keith Moon’s hotel swims, and you might.
Do you skew too?
Assuming you are reasonably competent, you can correct perspective using software, by skewing the canvas. This is a take on the old practice of tilting the paper easel with an enlarger. This was a limited-use technique, generally practiced by people who could not use view cameras and tripods but still had to come up with a presentable representation of a tall object. There were (and substantially still are) three issues here: crop, depth of focus, and dis-proportion. First, the crop came from the fact that tilting an easel meant that the projected image was trapezoidal and not rectangular, meaning that from the get-go, it had to be enlarged until the paper was filed. This still happens with digital. Second, the depth of focus issue is related to the fact that enlarging lenses are designed to project to a surface that is a uniform distance from the enlarger (i.e., projecting one flat field onto another). You would have to stop down the lens severely, or use a bigger focal length, which in turn required a taller enlarger column to maintain the same magnification.
The digitization of perspective correction uses computation to project the flat image onto a skewed plane, using interpolation and unsharp masking. This solves the apparent sharpness issue, but it degrades quality. Finally, dis-proportion comes from the fact that straightening converging verticals starts from a place where certain details are already compressed via the original perspective. For example, looking up at a tall building from a short distance, the windows look shorter (top to bottom) than they would if you were looking straight at the window from its own level.
So even when you manage to re-skew the canvas/field/whatever, you now have an image that is too “fat.” On enlarging paper, you would be forced to make a cylindrical correction to the negative (which is not practical in real life). On digital, there are specific transformations that you can perform to correct (for example, the adjustable ratios on DxO Perspective and Lightroom.
So skewing is a useful technique, but it’s still better to skew less.
Shifting your thinking: the mirror years
View cameras have used the concept of shift and tilt to adjust for situations where the viewpoint was wrong (shift) or depth of field was insufficient (tilt). Raising the front standard of a bellows-type plate camera was always standard practice to improve photographs of tall objects, especially in an era where wideangle lenses were not super-wide by today’s standards. Lens board movements were easy to achieve because there was always some distance between the lens mount and film plane in which to insert a mechanism to raise the lens relative to the film. And because there is no control linkage between the lens/shutter and the rest of the camera, you’re not losing automation. You never had any!
But these cameras were not small. The smallest bellows-type camera with lens movement features was the Graflex Century Graphic, a delightful 6×9 press-style camera. On many bellows-type cameras, though, there was no real provision for using a shifting viewfinder. The press-style cameras had wire-frame finders that provided a rough guide, but nothing could tell you whether the lens was actually level outside a gridded ground glass. Later in the game, the Silvestri H would present as the first camera with automatic finder shift, as well as a visible bubble level. Linhof used a permanently-shifted lens assembly (and viewfinder) on the Technorama PC series, and Horseman provided shifted viewfinder masks for the SW612P, though these were available only as “all the way up/down” or “all the way left/right.”
The shift mechanism, though, could not be adapted to SLRs easily due to three constraints:
- Most SLRs lenses are retrofocal – meaning that the nodal point of the lens is more than the stated focal length from the imaging plane. It takes a ton of retrofocus to insert a shift mechanism into an interchangeable lens that has to focus past a mirror box. More retrofocus means bigger lenses So when perspective control lenses began to appear for SLRs (35mm and 6×6), they were huge. Maybe not huge by today’s standards, but a 72mm filter size is pretty big for a Nikon SLR whose normal filter size is 52mm.
- To achieve an image circle large enough to allow shift around what is normally a 24x36mm image circle, it is necessary to use a wide field lens and stop it down severely (illumination with almost any lens becomes more uniform as it is stopped down).
- Most cameras can only meter PC lenses correctly in their center position, wide-open. Where shift mechanisms eliminate direct aperture linkages to the camera, you’re back to the 1950s in metering and focusing – then shifting – then manually stopping down to shoot (now corrected by the use of electronic aperture units in $2K plus modern Nikon and Canon PC lenses).
Viewing is not a lot of fun with 35mm SLRs; when stopped down, PC lenses black out focusing aids (like split prisms and microprisms) and still require careful framing to keep parallel lines parallel. So you need a bright screen – plus a grid or electronic level. Suffice it to say, a lot of people regard perspective control to be a deliberative, on-tripod exercise when it comes to SLRs and DSLRs. Maybe it’s not.
A new perspective: full frame mirrorless?
So here come mirrorless cameras (well, they came a while ago). Now you can fit any lens ever made to any mirrorless body. The optical results may vary, but at least physically, they fit.
— Getting the lens in place
So I grabbed the nearest available PC lens I could find, which was a 28/3.5 PC-Nikkor. Not AI, not even from this century. Released in 1980, it is a beast. I plugged this into a Konica AR body to Nikon lens adapter, and from there into a Imagist Konica lens to Leica body adapter. Why all these kludgy adapters? The answer is actually pretty simple: the Imagist has the correct tolerance to make infinity infinity, and the Konica adapter does the same. This is not a small consideration where you might be zone focusing a lens.
Then I plugged this kludgefest into a Leica M typ 246 (the Monochrom). Because why not start with the OG of mirrorless camera platforms? Of course, you can’t use a rangefinder with a Nikon SLR lens, so I plugged in an Olympus EVF-2 (which is the ‘generic’ version of the Leica EVF-2.
— Getting it to work
The Nikkor has two aperture rings. One is the preset, where you set your target aperture. The other is the open/close ring, which goes from wide-open to where the preset ring is set.
I turned on focus peaking and set the preset for f/22 and the open/close for f/3.5. I was able to establish that infinity was correct.
Next, I stopped down the lens (both rings to f/22), expecting that just as on an SLR, the EVF would black out. Worked perfectly.
I hit the “info” button to get the digital level, and it was off to the races. The lens has a rotation and a shift.
— But how well does it actually work?
The functionality is actually surprisingly good. On a Leica, it’s just stick the camera in A, stop the lens down to f/16 and 22, and point and shoot.
The digital level obviates the use of a tripod or a grid focusing screen, and you really just frame, turn the shift knob until the perspective looks right, and there you go. There are a couple of limits
You can’t use maximum shift along the long side of the film, but the only penalty is a little bit of a tiny shadow in the corner. And that’s with a full-thickness 72mm B+W contrast filter. You get 11mm shift up and down (i.e., along the short dimension of the firm) and 8mm left and right (nominally; as I stated, you can get away with more under some circumstances).
Aside from that, there are some minor annoyances like making sure you haven’t knocked the aperture ring off the shooting aperture. Or knocking the focus out of position (it’s a very short throw…).
BUT THE DUST! And here is the rub – shooting at f/16 and f/22 brings out every dust spot on your lens. Normally, you would shoot a Leica M at f/5.6, f/8 max. But PC lenses – like their medium and large format cousins – are designed to max out their frame coverage at very small openings. So I had never cleaned the sensor on my M246 in four years, and I got to spend an evening working on a hateful task that included swabs and ethanol and bulbs and the Ricoh orange lollipop sensor cleaner.
— And how sharp?
Very. Diffraction is supposed to start becoming visible at f/11 on this combination at 1:1, with it showing up in prints at f/22.
Pictures stand up to the old 1:1 test, except in the corners where you have over-shifted along the long side. Recall that in lot of situations, two of the last bits of corner are usually sky, where a tiny amount of blur is not going to be of any moment.
How well this will work on a color-capable camera is a question, especially since lateral color would come out. But right now, this is posing the most acute threat to 6×4.5 cameras loaded with TMY.