Format Conversion: A Project for Those Dreary, Wet Days You Rather Spend Indoors
by Bjørn Rørslett 

In a situation where rain is pouring down, a nature photographer needs any excuse, plausible or not, for staying indoors. Constructing your own optical devices is a fail-safe way of avoiding the wrath of the weather Gods. This time, I outline an alternate approach to getting a lens for dramatic and steep perspectives: Do a format conversion of a cine lens to make it work with your DSLR. Sounds difficult? Not really. Just read on to learn more about the ultimate DIY project for photographers.


Autumn Flowers
Roll Your Own Lens

© Bjørn Rørslett/NN

In order to get the conversion project going, I have gathered here an assemblage of useful items from my odds-and-ends drawers. The crucial parts are the Canon 6.5mm f/1.8 cine lens (upper row) and a lens for projecting the intermediate image from the cine lens onto the imager of the DSLR. I've used an elusive 19 mm f/2.8 Macro-Nikkor in this case, but a reversed 20 mm would do just fine.

The remaining items are a homemade "D" mount to 39 mm adapter, a Pentax screw-mount focusing extension ring, a K3 ring to provide an "F" bayonet for my camera, and various extension tubes with 39 or 42 mm threads, all of which have been scavenged from garage sales, used equipment bins at photostores or what have you. I never throw away anything that might prove useful later on.

Cine lenses for the small 8mm format can easily be picked up for next to nothing these days. That format as such is long dead, but the lenses might exhibit interesting features even today. Why is this? Surely they are so short in their focal lengths that they cannot possibly focus on a SLR? Yes, and no. It all depends on your commitment to the task at hand.

The very advantages with these lenses are in fact their very short focal length, and the general high optical quality of many of these designs. Using a short-focal lens means you can get your subject very close to the lens, thus providing a steep and dramatic perspective of your shot. Remember perspective is about the position of your lens with respect to the subject, not about the angle of view of the taking lens. Getting closer means getting a more exaggrerated as thus steeper perspective compared to the normal perception given by our eyes (and brain).

So, a supershort focal length allows for a very steep perspective. "All" that remains is getting that short lens to focus in a useful fashion for your camera, and that implies attaining infinity focus with it as well. To this end, an additional - intermediate - lens must be included in the optical pathway, otherwise the setup will fail.

Almost There. The 6.5 mm lens porject

Almost There
© Bjørn Rørslett/NN

Shown here is the format-converted 6.5 mm Canon lens assembled into fewer and more recognizable modules.

Top to bottom depict as follows; the 6.5 mm Canon lens mounted onto a 39-42 mm thread adapter, the intermediate lens (a 19 mm Macro-Nikkor) in its focusing stage made from a Pentax focusing tube, with 42 mm thread, and a rear tube with 42 mm thread in front and a 42 - 52mm thread to provide a mounting point for an "F" adapter to the rear.

The critical item in the project is the intermediate lens. This optic has the dual task of making the front lens focus properly, besides its rôle as a projection lens to relay the image from the first lens onto the final imager in the camera. Since the image circle emanating from the cine lens is smaller than that needed by the camera, additional image magnification is called for. There is also a need for getting sufficient space between the front lens and the camera, otherwise you cannot hope to get infinity focus when the reflex mirror sits in the optical pathway. Obvious, when the rear flange to film distance of the cine lens is just a few millimeters, something other than ordinary extension is called for. A relay lens is the answer.

During the years I have made relaying optics by several different approaches. The easy one is reversing a wide-angle lens on a bellows unit to give the needed magnification of the intermediate image. Depending on the magnification you need, lenses from 35 to 20 mm are appropriate. Even better suited are lenses made for photomacrographic work, the so-called (true) "macro" lenses. Such lenses are, or rather were, produced by Zeiss (Luminar), Leitz (Photar), Nikon (Macro-Nikkor), and other companies supplying optical gear to scientific labs. If you can find, or afford, any of these lenses, they are really outstanding for the task at hand. In my 6.5 mm lens project, I have used various lenses during the evolution from a prototype (built some years ago) to the current Mk.II depicted here. I initially used a 24 mm Nikkor reversed, then a 20 mm Zuiko lens, to end up using a 19 mm Macro-Nikkor. This shows there is no solution set in stone for format conversion projects. Any spare lens which is available and works, will do just fine.

In whatever fashion the intermediate image is magnified and relayed to its final destination, you have to accept that it ends up being seen upside-down. Or rather, the image arrives correctly oriented at the camera, but camera viewfinders are designed to turn the incoming image upside-down to make it look "normal", so in the end the image is right but wrongly displayed. Magnifying the image means getting a less effective speed of the lens array. The viewfinder tends to get dark and you often need some additional lighting of the subject in order to focus accurately. All of this is just something you have to accept and for old hands hardened from experience with view cameras, yesterday's news anyway.

Water Colours, by AFS 200/2VR and D1X

The Assembled Lens Array
© Bjørn Rørslett/NN
Small, light-weight, and very special. Just the way I like my gear (sometimes)


Move It
© Bjørn Rørslett/NN

The 6.5 mm Canon lens mounted on my trustworthy D1X camera.

I recently added another cine lens to my collection, namely, a 10 mm f/1.8 Cine-Nikkor. This Nikkor was converted using a 25 mm f/3.5 Zeiss Luminar as the intermediate optic. At the time of writing I haven't used this setup sufficiently to ascertain its qualities, but this will occur in due time.

To what end?

So, you end up with an optical contraption all of your own, but to what use should this strange optic be put? Don't let the short focal length fool you into thinking you'll get a superwide view of the world. This is not what you get and hardly surprising, because cine lenses are designed for correspondly smaller field of view than 35 mm format lenses. My 6.5 mm Canon behaves like a 35 mm lens on my DSLRs, nothing wider than that, but with the added advantage of being much shorter in focal length. Thus, I can focus this setup to within a centimeter of the front element and still get ample depth of field in conjunction with a very steep perspective. The equivalent simply isn't possible with lenses for 35 mm and DSLR photography.

Using these format-converted lenses is a heap of fun really. You do have to move around quite a bit more than normal to locate the suitable position for a shot. In general, you need to move really into the subject. Also, there is the issue with a darkened viewfinder which can be a constraint unless you do some planning of the shooting in advance.

Given the proper shooting technique and a stable support for the camera, surprisingly sharp images are attainable from these cine lenses. A few examples are presented below to illustrate this point.

Wood Sorrel

Wood Sorrel
© Bjørn Rørslett/NN

The Wood Sorrel (Oxalis acetosella) is a small-flowered spring species, and getting close-ups of these delicate flowers while a good depth-of-field is maintained is not an easy task for the nature photographer. The 6.5 mm Canon lens mounted on my D2H did the trick, though.

Wood Anemones

Wood Anemones
© Bjørn Rørslett/NN

This shot of Wood Anemone (Anemone nemorosa) was acquired using my F4 and the 24 mm Nikkor as an intermediate lens. The floor of this wood was quite dark, and in order to stop wind-induced movement of these pretty flowers, a flash was put to its intended use.



I could never have accomplished these conversions without the assistance of lenses given to me by kind people. Thanks go to Paul Hofseth and Paul D. Wilson for providing me with the 6.5 mm Canon and 10 mm Nikkor, respectively. Ove Bergersen directed my attention to a Nikon Multiphot photomacrographic camera with a complete array of Macro-Nikkor lenses, including the 19 mm used here.

Format Conversion: A Project for Those Dreary, Wet Days You Rather Spend Indoors  

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Last Update 10 November, 2004