Introduction
Like most photographers, there is nothing I enjoy more than looking through the second-hand lens listings at the back of AP or browsing the used lenses in the window of a camera shop. No matter what camera I am currently using, or how many lenses I have, there is always another lens that I want. This can be anything from a classic but reasonably priced wide-aperture 50mm lens to a hideously expensive 30-year-old fisheye lens.
While many of my used lenses are fully compatible with my current camera, some can only be used with certain restrictions. A few are not even designed for my camera, which means finding a way to fit them. Thankfully, no matter what your current system, there are ways to adapt and use older second-hand optics designed with a different lens mount.
Legacy Mounts
Of the current crop of DSLRs, Nikon and Pentax have the longest established lens mounts. Although both the Nikon F mount (seen in photo) and the Pentax K mount have been adapted over the years to enable technologies such as electronic aperture control and autofocus, the basic bayonet mount of each has remained the same. With the F mount being more than 50 years old and the K mount being more than 35 years old, there are hundreds of different lenses available ranging from basic fixed-focal-length lenses to the more exotic, such as the Pentax 15mm f/3.5 and the TV-Nikkor 35mm f/0.9 lenses.
With a handful of exceptions, most Nikon F-mount and Pentax K-mount lenses will fit onto contemporary Nikon and Pentax DSLRs. However, with no autofocus and a manual aperture control there are some restrictions as to how these lenses can be used. For more on this see the Using manual-focus lenses on modern DSLRs below.
Although not as old as the Nikon F or Pentax K mount, the Sony Alpha mount is the same as the older Minolta Dynax mount (which was actually named the Alpha mount in the Far East). Again, all the Minolta Dynax-mount lenses will fit Sony Alpha DSLR cameras, with full AF and aperture control. Canon changed to a completely new lens mount when it introduced EOS autofocus cameras and lenses in 1987. However, with the mount being more than 20 years old there are a number of bargains to be found among the early EOS AF lenses.
Olympus was slow to develop an autofocus system for its cameras. It based the AF system around its existing OM mount, but this didn?t prove popular and it concentrated its efforts elsewhere. In collaboration with Panasonic, Olympus now uses the Four Thirds and Micro Four Thirds mounts in its digital interchangeable-lens cameras, although it does produce a mount adapter that enables OM lenses to be manually used on Four Thirds cameras.
One type of lens to look out for is Tamron Adaptall or T-mount. These lenses were produced by Tamron and feature an interchangeable lens-mount that can be changed to fit most cameras. The advantage of this approach is that rather than buying a whole new lens if you change camera system, or have two different cameras, all you have to do is replace the T-mount.
While it is still possible to buy proprietary T-mount lens adapters for most camera fittings, the majority are now of third-party manufacture in the Far East and not always the best quality. However, with T-mount lenses still being popular and with some telescopes and spotting scopes being able to mount to cameras via a T-mount adapter, there is still a demand for the mounts. In fact, there are many T-mount adapters for mounts that didn?t even exist when Tamron stopped manufacturing T-mount lenses in the late 1980s, such as the Four Thirds and Micro Four Thirds mounts.
Mount Adapters
The simplest and most obvious way to attach a non-proprietary lens to your camera is to use a mount adapter. These are simple metal adapters that fit onto
the rear of a lens and convert the existing mount to an alternative one. One of the most popular mounts to convert is the M42 mount (seen in the photo). 
This simple 42mm screw-thread mount has been used on a number of cameras since it first appeared in 1949 on the Zeiss Ikon Contax S, and it was popularised in the 1970s by Pentax, Praktica and Zenit. As a result, there are plenty of second-hand M42-fit lenses, and the simplicity of the mount means that the adapters are available to fit M42 lenses to most contemporary DSLR cameras.
A quick search online shows that there are a huge number of adapter mounts available, enabling all sorts of camera and lens mount combinations. It is even possible to fit medium-format lenses onto SLR lens mounts should you so wish. However, there are some physical limitations as to what can be adapted. First, the flange-depth of the original mount must be greater or equal to the flange depth of the mount you wish to use. If the flange-depth distance of the alternative lens is shorter than that of the camera mount, it may still be possible to adapt and mount the alternative lens, but infinity focus may not be possible or the adapter will have to use an additional lens to allow infinity focus, which may affect image quality.
Medium-format systems usually have a far greater flange depth than 35mm-style cameras. This means that it is possible to mount most medium-format lenses to most DSLRs via a large conical adapter that looks like an extension tube. While there is often a novelty factor behind using medium-format lenses on a DSLR or 35mm camera, there are also some genuine reasons for doing so. For instance, when using a medium-format lens on an APS-C-sized sensor DSLR, only the very centre or ?sweet spot? of the lens is used.
Lenses are sharpest at their centres, so sharpness is high and curvilinear distortion is minimised. Some adapters can also be found that have a tilt-and-shift mechanism, which can quickly turn a medium-format lens into a affordable tilt-and-shift optic. However, medium-format lenses often have a lower optical resolution compared to 35mm lenses, simply because the resulting image has to be enlarged less.
Using Manual-Focus Lenses On Modern DSLRs
Once a manual-focus lens is mounted on a DSLR there are few restrictions as to how the camera and lens can be used. As older manual-focus lenses have no electronic connections, the camera will not recognise the lens that is attached. By default, many cameras will not allow an image to be captured if a lens isn?t detected. However, this can normally be changed in-camera by looking for a custom setting called Shoot Without Lens or similar. 
Once the camera?s shutter is able to fire, the most obvious restriction is that there will be no autofocus and the ability to adjust the aperture using the camera controls is lost. With the loss of these automatic features it is best to operate the camera as you would a manual SLR. The shutter must be adjusted on the camera, while the aperture must be adjusted on the lens. As the camera can?t control the aperture the camera must be in aperture priority or manual exposure mode.While the camera?s metering system should work satisfactorily, if you want to stop the lens aperture down you may find that there is not enough light entering the camera to enable you to focus accurately.
The best way around this is to set the lens aperture wide open when focusing. Some manual-focus lenses have an auto and manual setting, not for the focusing, but for the aperture blades. When set to auto the aperture is wide open, which lets in light to allow for focusing. On pressing the shutter release a lever in the camera shifts a lever on the lens, which stops the lens down to your chosen lens aperture. The chances are that if you are using a manual focus lens with an adapter, this mechanical connection will be lost. If you are using one of these lenses on a DSLR it is best to leave it set to the automatic position when focusing, or set it to manual and open the aperture. Once a manual lens is correctly focused, stop the aperture down to give the required depth of field. This will allow the camera to correctly meter the scene before you release the shutter to take an image.
Holding the Lens
Enlarger lenses are a favourite with macro workers because, when mounted on the end of a bellows unit, these flat field optical designs produce excellent results at short distances. For macro work it is easy to take advantage of the short back-focus of these lenses as they are designed for use with a negative placed close to the rear element, and when mounted with a greater distance between the rear element and the back focus point (the film or the sensor) infinity focus is lost, but close focus is gained.
Here we show you how these lenses can also be used for normal subject-distance photography. To gain infinity focus, the rear of the lens needs to be closer to the sensor than is possible with a normal DSLR so the answer is to create a mount that recesses into the body. However, as these lenses have no focusing movements of their own, attaching them to a fixed mount delivers only a single focus distance, which becomes very restrictive. What is needed is a rack-and-pinion system that can shift the lens between different distances from the sensor to create infinitely variable focus. This isn?t practical unless you are prepared to build your own system, in which case the time and effort will probably outweigh the value of the results.
While it is a little hit and miss, handholding the lens in the throat of the camera works a treat with a little experimentation and it is brilliantly flexible. If you wrap your fingers around the lens to stop light entering the camera close to the elements (see above right), you can get some excellent results.
I used this £16 Wray 2in Supar f/4.5 lens wide open and held it in the throat of a Samsung GX-20 (see below). You can hold it straight on if you like, or twist it slightly to alter the plane of focus to deliver a tilt-and-shift lens effect. So long as you are blocking most of the light with your hand and are able to judge focus in the viewfinder, it is a quick and easy method of obtaining unique images, infinitely variable focus and selective-plane, extreme shallow depth of field.
Flange Depth
Put simply, flange depth is the distance between the lens mount and the film or sensor. Each camera system has a specific flange depth, with the Canon FD mount having a flange depth of 42mm, the Canon EOS mount 44mm and the Nikon F mount 46.5mm, while the lack of a mirror box means that the Micro Four Thirds system can have a flange depth of just 20mm.
To enable a third-party lens to attach and focus on a modern DSLR correctly, the distance between the lens mount and the camera image sensor must be the same as it would be for the lens and the camera it is designed for. This allows the lens to correctly focus on the camera?s image sensor. If the flange depth for the third-party lens is less than the flange depth of the camera, then it will not be able to correctly focus on the sensor with a standard mount adapter. Instead, an adapter with a correcting lens element can be used, but this can have a detrimental effect on image quality. 
If the native flange depth of the third-party lens is greater than it would be for a proprietary lens, then an adapter can be used to make up the distance so that the third-party lens is placed the correct distance from the sensor so it can correctly focus. For example, Micro Four Thirds cameras have a flange depth of 20mm, while the Nikon F mount has a flange depth of 46.5mm. So by making a mount adapter that is 26.5mm deep (46.5mm ? 20mm), Nikon F-mount lenses can be fitted to a Micro Four Thirds camera with no compromise to the ability of the lens to focus.
However, at a distance of 46.5mm, the Nikon F mount has the largest flange depth of any current SLR system. As a result, lenses from other camera systems cannot be mounted via an adapter without infinity focusing being lost, or without a lens element having to be used in the adapter to retain infinity focus.
1 – Each camera system has a specific flange mount depth, so lenses can focus correctly
2 – If you try to attach an alternative lens designed for a different mount, it may not correctly focus
3 – By using an adapter, the lens can be spaced so that it correctly focuses on the camera?s sensor
Bellows
Bellows
The lenses found on older folding bellows cameras are generally a lot simpler than today?s optics, comprising fewer lens elements and relying on the camera?s bellows to move the lens back and forth to focus.
Most folding bellows cameras use medium-format film. To produce an imaging circle large enough to cover this film size, the lens has to be positioned far further from the film plane than a lens found on a 35mm or digital SLR. This means that the relatively simple lenses found on bellows cameras can be used on modern SLRs.
The easiest way to use one of these lenses is via a macro bellows on an SLR. Although typically bellows are used for macro photography, by attaching them to a lens from a bellows camera and the other end to a DSLR camera, you are, in effect, just replacing the original bellows from the camera the lens came from.
Macro bellows are available for most camera mounts, with prices for new bellows costing as little as £50, although you may be able to find them even cheaper second-hand. Attaching the lens requires a little ingenuity. The lenses on folding bellows cameras are usually held in place with a retaining ring on the rear of the lens. The easiest way to attach one of these lenses to a bellows is to use electrical or cloth tape to hold it in place, but it isn?t too difficult to make a mount for it using a camera body cap (see below).
Making a mount for a folding bellows camera lens
I bought a Carl Zeiss Jena Tessar 12cm f/4.5 Compur lens for a few pounds on an online auction site. This lens was used in a variety of bellows folding cameras in the late 1920s and early ?30s, but with a few small modifications it is possible to make a mount so it can be used with a modern set of camera bellows.
Skill Level: 2/5
Time to complete: 15 minutes
You will need:
- A lens from a medium or large-format folding bellows camera
- A camera body cap that matches the mount of your macro bellows
- A hobby drill and coping saw
- Strong glue or tape
| Step 1 | Due to not having a coping saw to hand, I used a hobby drill to make holes all around the inner circle of the body cap. Once there are holes all the way around the inside of the body cap, you should be able to push out the centre to leave just a circular mount. |  |
| Step 2 | After sanding the inside edge of the body cap you are ready to attach the folding bellows camera lens. |  |
| Step 3 | Fit the lens to the body cap. You may be able to do this using the retaining ring on the rear of the lens, or by simply using some electrical tape. For a more permanent solution try using superglue or epoxy resin to fix the lens to the body cap. |  |
| Step 4 | Now all that is left to do is mount the camera bellows to your camera and the new modified lens to the other end of the bellows. You can then move the bellows back and forth to focus. |  |
See also:
