Tilt-shift bellows

Large-format view cameras consist of two standards that can slide on a rail or a similar mechanical system. A standard is, basically, a metal or wood plate and associated mechanical parts. One of the standards carries the lens. The other standard carries a ground glass onto which the image is projected. Light-tight bellows connect the standards. The image on the ground glass is used for framing and focusing. Once the picture is composed, a photographic plate carrier is inserted in place of the ground glass, and the exposure is taken. Most lenses used with view cameras possess a shutter, usually placed between optical elements and near the diaphragm. Focal plane shutters for view cameras do exist, but they are rarely used. Most view cameras allow the use of a large- or medium-format film back that accepts film rolls (usually types 120 or 220). Digital backs for view cameras are also used.

Besides film/sensor size, the characteristic that distinguishes view cameras is that both standards allow a wide range of shift and tilt movements. Field cameras, which are also made for medium- and large-format film and have bellows, allow a much more restricted set of movements (typically at the lens standard only). As their name implies, field cameras are meant to be used primarily in the field, and can be folded into a still large, but more manageable box for transportation and protection of the delicate mechanisms. View cameras typically are used in the studio, or in interiors.

In part of the photographic literature, shift is used to indicate lateral translation movements of a standard, and rise and fall vertical ones. In the present discussion, I use shift to indicate both vertical and horizontal translations, because their effects on image geometry are the same.

Tilting and shifting the standards provide a variety of effects. Shifting the lens and/or film standard allows e.g. tall buildings to be shot from ground level without perspective deformation (i.e., the sides of the building remain parallel to each other in the photograph instead of converging toward the top). Shifting in the opposite direction provides an exaggerated perspective that can be used, for instance, to simulate the effect of an extreme wide-angle lens. Tilting the lens with respect to the film/sensor plane provides a focus plane of the subject that is not parallel to the film/sensor plane. This is useful, for instance, for shooting a floor scene obliquely from a higher vantage point, and achieving focus simultaneously on all parts of the floor. Without tilting, only elements at a given distance from the camera (e.g., in the foreground) can be in perfect focus, but not those at other distances. With an ordinary camera and lens, like a DSLR, this problem can be partly solved by closing the diaphragm. However, the result may not be totally satisfactory, especially in macro photography. Close-up and macro photography with a view camera capable of tilting, instead, allows this effect.

With the same type of subject, tilting the lens plane in the opposite direction achieves focus only along a narrow line of the floor, and simulates the use of an extremely fast lens (see example below). This is possible even in landscape photographs (especially buildings and urban landscapes taken from a high vantage point), which in this way acquire a unique appearance. The results look eerily like pictures of miniature artificial landscapes, because they simulate the narrow depth of field characteristic of macro photography.

There are several designs of view cameras, but most of these cameras are precision mechanical equipment. One of the design types preferred by professional photographers for its convenience of use employs L-shaped metal frames to hold the front and rear standards. This design, known as L-frame, allows tilting without unduly affecting focus and shift.

Small-format SLR and DSLR camera bodies lack tilt and shift capabilities. A few medium-format SLRs have built-in bellows with limited shift and tilt of the front standard. With a Nikon DSLR, there are essentially two ways to add shift and tilt capabilities:

1 - Use a tilt-shift lens. Currently, the only such lens made by Nikon is the PC Micro Nikkor 85mm f/2.8 D. Nikon used to make several other PC (= perspective control) lenses, but all of these had only shift capabilities. Hartblei and Arax make tilt-shift lenses for Nikon and other bodies, based on the optics of medium-format lenses made in ex-Soviet countries. Canon tilt-shift lenses are sometimes custom-modified to fit on Nikon cameras, usually at the expense of either shift or rotation capabilities (tilt and shift with these lenses is possible along one axis only, and the whole lens rotates about its mount to provide tilt and shift along an arbitrary axis). Arax also makes a shift-only adapter for mounting medium-format Pentacon 6 or Mamiya lenses on a variety of SLRs and DSLRs. Varioflex lenses are early tilt-shift designs for 35 mm SLRs.

2 - Use a lens mounted on bellows that provide tilt and shift movements, usually of the front standard only. Almost all these bellows are clumsy to use in practice, because the front standard tilts and shift horizontally. In order to perform these movements vertically, which is by far the most frequent direction in practical photography, you must rotate the bellows sideways (including their tripod mount). Some bellows (e.g., Edixa) allow tilt and shift only in directions perpendicular to each other. Several companies marketed tilt-shift bellows at one time or another, but these models can be difficult to find on the second-hand market. Novoflex probably is the only company still manufacturing one such model, albeit very expensive (it costs as much as, or more than, a good tilt-shift lens, and lenses for these bellows must be purchased as extras). A (probably incomplete) list follows:

Zörk makes a tilt/shift adapter and a focusing tube that can be assembled together and used with enlarger lenses. Tilting is carried out by a ball-joint that can be tightened with a collar. This arrangement seems to be unique among tilt-shift lenses and adapters. This setup looks interesting, but it is also extremely overpriced. A few web sites describe custom modifications to bellows for giving them, or facilitating the use of, tilt-shift capabilities.

3 - This is the third solution in the list of two possible solutions. If your purpose is to achieve a correct architectural perspective when shooting buildings from ground level (or any other tall subject shot from a lower or higher vantage point), there is one more alternative to the use of shift lenses or bellows. Use a wide-angle lens, and shoot with the lens axis horizontal. The focal length of the lens, of course, must be sufficiently short to include all of the building you want to shoot. Likely you will also need to turn the camera so that the longer size of the picture is vertical. About half of the picture taken in this way will include the ground. Since this is unlikely to be interesting, crop it away in post-processing. What is left is a picture of the building with its sides parallel to each other (depending on how good the lens is - you cannot hope for good results with a cheap lens suffering, e.g., from pincushion or barrel distortion). Except for a lower pixel-count, the result is exactly like a picture taken with a shift lens.

Shift-only lenses are largely obsolete in digital photography, unless you need to achieve the maximum possible resolution. In addition to the workaround described above, software can easily turn converging lines to parallel ones in post-processing. On the other hand, the only way to simulate tilt movements is by a lengthy process of selective blurring in post-processing. Other than by using very narrow lens apertures and accepting the unavoidable loss of resolution caused by diffraction, there is no way to simulate the selective increase in depth-of-field provided by lens tilt. Thus, tilt is more useful than shift.

Lenses with built-in tilt-shift come in a variety of focal lengths (roughly 28 to 85 mm) and are generally expensive. Commercial bellows force the use of lenses with rather long focal lengths (roughly above 100-150 mm) if focus to infinity is required. In some cases, deeply recessed lens plates can be used to allow lenses of shorter focal lengths to focus to infinity.

I have been lucky enough to acquire a set of second-hand Kenlock "Swing & Shift bellows" (as named on the original box). I have failed to find any documentation, as well as information about this model on the web.

The above is not a large-format view camera. Repeat with me: "The above is not a large-format view camera." This is indeed a set of Kenlock tilt-shift bellows (even though Kenlock did call them by a slightly different name). They are designed for 35 mm SLR cameras, and originally came with several adapters for different makes of lenses and bodies. I was able to modify some of these adapters to fit Nikon DSLR bodies and a variety of lenses. I use them mostly with EL-Nikkor lenses designed for enlargers. The above picture is not the way these bellows looked originally. It shows them after the modification discussed below. It also shows the bellows attached to a large Manfrotto plate (at the bottom).

These bellows are essentially a miniature copy of a view camera with L-frames, and provide ample amounts of tilt and shift of both standards. However, Nikon DSLR bodies are considerably larger than most old SLR bodies, and this restricts the range of movements of the rear standard. In fact, I was forced to disassemble the bellows (which originally had the vertical portions of the L-frames on the right side when seen from behind the camera, where they collided with the "handle" of the body), and reassemble them with the L-frames on the left side, where they are slightly less obtrusive. This required a small amount of machining in addition to reassembly, and was not possible without loosing part of the range of the gear for upward shift of the front standard, because of the new location of its gear knob. The full amount of shift is still possible, albeit without using the gear for its highest portion. I was also forced to manufacture an adapter ring for the camera body with a total thickness of about 10 mm to provide clearance for the controls on the front of the camera. It introduces the undesirable effect of decreasing the maximum focusing distance of mounted lenses, but there is no easy workaround to this. Even Nikon bellows have a similarly thick camera mount at their back.

With 6 gear knobs, 14 tightening knobs and 15 printed scales, these bellows are not equipment for fans of point-and-shoot photography. Just like a view camera, these bellows require you to take time to understand the basics of view camera operation, the effects of combined tilt and shift, and the Scheimpflug principle and its application. To begin with, you should look for any or all of these references, some of which are available on the web (e.g., http://www.trenholm.org/hmmerk/):

Hicks, R. & Schultz, F., 2001: Medium and large format photography; Moving beyond 35 mm for better pictures. 160 pp., Amphoto Books, New York.
Merklinger, H.M., 1992-1993: The Scheimpflug principle. Series of articles in Shutterbug, November 1992, January, February, March 1993 issues.
Merklinger, H.M., 1996: Principles of view camera focus. 7 pp., Internet article.
Merklinger, H.M., 2007: Focusing the view camera. 146 pp., Internet edition by the author.
Simmons, S., 1987: Using the view camera, revised edition. 143 pp., Amphoto Books, New York.

Once you understand the principles and practice, you must take time for each shot. Fortunately, unlike with large format film, with a DSLR you can shoot to your heart's content at no cost. However, especially while learning, you should write down the tilt, shift and extension settings of the bellows, lens aperture and all other relevant variables, so that you have a chance to understand what you are doing wrong when you don't obtain the results you expect. You cannot evaluate focus accurately by looking at the camera's LCD, so you still need a paper trail to follow when examining the results on your computer screen. Needless to say, you need a solid tripod, a precise head and a remote shutter control, and you should use mirror lock-up if your camera provides this. In spite of their metal construction, these bellows do suffer from a slight amount of flexibility, because of their many moving parts.

With significant amounts of tilt and shift, your camera likely will not meter correctly. Light will hit the exposure sensors at angles wildly different from those the camera was designed for. The camera may even spot meter at points different from those indicated in the viewfinder. You may find out by trial-and-error an approximate exposure compensation to use with a given amount of tilt and shift, but be prepared to bracket and control the histograms on the camera's LCD, because each shot may need a different exposure compensation. Focusing is of course manual. In addition, likely you must focus for parfocality rather than pin-point sharpness (i.e., you must make judicious use of the available depth of field, instead of concentrating on maximum focus at one given point). The Nikon D80 and lower models do not meter at all with these bellows, and manual exposure is the only possibility. Trial-and-error exposure by checking the histograms on the camera's LCD is entirely feasible with these models. In my experience, the D200 does not fare too badly with aperture-priority exposure, and is off by no more than 1-2 stops at extreme tilt and shift settings.

With practice, things become simpler than suggested by the number of controls on the bellows. In practice, most of the time you need to change only the vertical shift and tilt of the front standard (for tilting the focus plane) and the distance between standards (to change the reproduction ratio), and focus with the geared base of the bellows (or a focusing rack if you are not using bellows with this facility). Even with only four variables, however, the process is gradual and time-consuming.

The choice of lenses to use with these bellows is restricted. The standards must be moved apart by a few cm in order to allow shift and, especially, tilt. In practice, this means that only focal lengths of 105mm, 135mm or higher can focus to infinity. Even an EL-Nikkor 75mm can focus only at a minimum reproduction ratio of about 1:3 with the bellows fully closed (and therefore with no tilt and shift). An EL-Nikkor 63mm provides a reproduction ratio around 1:1 with the bellows closed. A lens with a very narrow barrel, like some Luminar and Photar macro lenses, could be mounted in a custom-built very recessed lens board. This might allow the use of 50-60mm lenses, but probably limits the maximum lens speed to about f/4. On the other hand, an Olympus OM Macro 135mm f/4.5 for bellows, modified by changing the Olympus rear bayonet to a Nikon one, focuses to infinity on the Kenlock bellows with enough extension between the standards to allow a large amount of combined tilt and shift (a good 25° and 15 mm, which already exceeds the capabilities of the lens and causes a very visible loss of sharpness). In practice, it seems this lens can be used with a maximum of about 15° of tilt and 10 mm of shift. It is designed to cover a 24x36 mm frame, which provides a reasonable shift margin.

Above is an example of macro photography without tilting, at a reproduction ratio around 1:1. The depth of field is limited by the lens aperture (f/4). An EL-Nikkor 75mm f/4 was used.

Even closing the diaphragm to f/16 does not provide sharpness across the whole field.

An appropriate amount of tilt increases the apparent depth of field without requiring the diaphragm to be closed past f/4. Strictly speaking, the true depth of field remains the same at a given aperture, but tilting the lens effectively tilts the focus plane to make it conform to the subject.

Tilting the lens in the opposite direction reduces the apparent depth of field (additional adjustments in shift and positioning of the whole camera are also required to reframe). This effect is similar to taking a picture with a super-fast f/1 or f/0.5 lens fully open (assuming one could find such a lens). Alternatively, the depth of field is visually similar to the one you could obtain in the super-macro range, with a reproduction ratio around 10:1 to 20:1.

When using tilt, shift should be adjusted to minimize vignetting, which is caused mostly by the walls of the mirror well of the body. When bellows are extended just a little, shift must also be adjusted in order to allow a sufficient amount of tilt, because pleated bellows are rather stiff. Using bag bellows (i.e., a square, rather large bag-like structure instead of pleated bellows) makes the operation easier. Bag bellows are available for view cameras, but they are too large for use with DSLRs. Suitable bag bellows can be sewn from soft leather (this material is used in professional products) or other suitable, pliable and light-proof materials. Many of the black soft leather bags that are provided with photographic accessories (and that are largely useless for their storage) are light-proof and can be converted into bag bellows.

Shift alone affects perspective, but not depth of field. Tilting about the back nodal point of the lens should in principle leave perspective unaffected, but this may not be allowed by the design of these bellows. An appropriate combination of tilt and shift can achieve the same effect. However, an amount of shift exceeding 10-15 mm almost always causes vignetting. The maximum amount of shift without vignetting is not necessarily shown correctly through the viewfinder, because the mirror is also a source of vignetting. Observing actual pictures gives more reliable results.

An additional problem is that generic lens shades are not designed for tilt/shift photography. You may solve the problem of vignetting by using lens shades designed for lenses of significantly shorter focal lengths, but this means that the lens is more vulnerable to flare. As far as I am aware, there is no solution to this problem. In principle, it could be possible to design a tilting lens shade, or a bellows lens shade with tilting capabilities, but this would add to the complexity of this type of photography.