The Reversing Back assembly. A shows the basic frame and the parts that have to be cut away. B shows the position of the channel for the lip of the film holder to drop into and the position, and of the three extra wooden side pieces.
When finished, this whole unit drops into the camera back and rests on the frame that will also support the back of the bellows. Because it is perfectly square it can either be put in the camera in the landscape or the Portrait position.
The Tripod lock. A small brass plate is screwed or let into the base unit above the focusing rod. A 2BA thread brass knob is inserted into this via a treaded hole. When the knob is screwed down it inhibits the axle turning so locking the focusing movement.Whether or not you put a lock on is up to you.
Tripod fixing. I use the left hand method. A brass bush is inserted from below and a circular plate is screwed to it from above. The right hand and simpler method is to insert a bush from an ERC camera case as described in the text opposite.
The back fixings are very simple and self explanatory. They hold the frame for the film holder in the camera back recess.
The Reversing Back
The only part of the construction left to do is the reversing back and focussing screen holder. The back is another frame, this time measuring 164mm square. Use 8mm wood and make the frame from strips 30mm wide. When this is all mitred together it should drop neatly into the recess you formed in the camera back. The hole in the middle should measure 104mm square. This whole unit will eventually become the holder for the film holder. I use Fidelity cut film holders so the measurements given will suit these. If you are planning to us another make of film holder then it is a simple matter to adjust these measurements to fit.
The next step is to open out the hole in your frame to suit the holder. It is already wide enough for your purpose, but you will need to adjust the top and bottom. Mark it top and bottom for convenience, and then remove a rectangle of wood 13mm x 104mm from the top and 4mm x 104mm from the bottom of the opening. You will now have an opening about 120mm x 104mm, the size you need for the film to see the image. Cut film holders have a ridge just above the film opening, which stops the slide pulling out of the camera when you remove the sheath for exposing a film. You must cut a channel in your back for this to drop into as the slide is inserted. It should be 3mm above the film aperture and run the full width of the slide and about 1.5mm deep. Now for the sidepieces to hold the slide in place; the slide is just under 12mm thick so use the 12mm wood cutting two 150mm strips 15mm wide and one piece 152mm x 5mm. Chamfer the outside corner to provide clearance for the retaining clips. Glue and screw these in place around the slide opening, as shown in the diagram. When the glue has set, rub the extra thickness off so they are flush with your film holder once it is in place. Again, use a sheet of glass paper lying on a hard flat surface.
The Focusing Screen
Next, you will need to make a frame to hold the ground glass for focusing. This is another simple frame to fit your 5x4 in sheet of ground glass. Its aperture must line up with the one on your film holder and the ground side of the glass must match the register of the film in the slide. In this case, it should be 5mm in from the front edge. If doing this accurately by cutting is a problem, simply make the frame opening the same size as your ground glass and glue a thin strip of wood 5mm deep x 3mm wide around the frames inside so that one edge is level with the front.
Now we come to the controversial bit. I use a sliding strip of brass each side to hold the film holder or screen in place. A larger version of the one used to hold the lens panel in place. Backs involving springs are more widely used, but can play havoc with the camera's alignment, however rigid it is. I find film holders and focusing screens can be interchanged, as one goes to take a photograph ,much more easily using sliding catches. The illustration will show you how they work. I also have a locking knob each side to make sure that once in place, the holder cannot fall out of the camera. It may not be as smart or as fast to use as the more usual methods, but at least it is sure and does not upset anything.
Odds and Ends
The last to things to think about is a focusing lock and a tripod bush. Taking the lock first, some may thing this is not necessary. If you want one, fit a screw with a small knob so that it can bear down on the focussing rod. The diagram has a suggestion.
Next, we come to the all important tripod bush. Put this in the middle of the base unit; I make mine with a 1/4 Whitworth tread. You can also use a flat small rectangular piece of brass drilled and tapped to that size, screwed inside the base under the focusing platform. A source of tripod bushes can be the retaining screws from discarded E.R.C. camera cases. Cut off the bit that goes into the camera and drill holes to fix it to your baseboard. Again, see the illustration.
Most of your work is now finished. All that remains is to make a few simple clips and catches for holding things in place. I sometimes make fittings for carrying handles or simple hooks to hold the camera shut when folded. The picture shows you a way of securing the reversing back you have just made on to the camera.
Final finish
Having built you camera, I am afraid you must take it apart again. We have at last come to the important business of finishing the thing, something that is both better and easier if it is in pieces again. There are three ways of finishing it. For non-metal parts, you can use varnish, paint or treat with Danish oil. Whatever method you use, rub it down to the smoothest possible finish all over. The more coats you give it the better will be the finish. Some people use polyurethane varnish but I use the clear acrylic lacquer intended for spraying motorcars. It is tough and long lasting. The first few coats sink into the wood but in time with light rubbing down between the coats, a very good surface builds up. Take the usual precautions if using spray paint and wear a suitable mask.
If you build your camera from alternative materials cover some of the body parts with either leather cloth or the paper that simulates leather. This later material is quite durable if given several coats of varnish. I used this method with the first camera I built all those years ago. You saw the result in the first section of this workshop.
When it comes to the metal parts of the camera, I use the clear lacquer spray again. Several coats of this seem to be quite durable. I have several cameras treated in this way that have lasted well over the years. If any of the parts look a little shabby after prolonged use they can always be cleaned and re-sprayed. The old time brass and mahogany cameras used a shellac varnish that aged to a wonderful colour, on all their brass work.
Fitting the Bellows
When you have finished your camera to your own satisfaction and you have to re-assemble it. The last thing to do is to fit the bellows. For the front I usually make a small metal frame that fits inside the first fold and screw this to the back of the front lens holder frame. The back fixes onto that unit using two metal strips screwed through the final folds of the bellows and some glue.
When it is all completely finished, I take it into a darkened room and check it for light leaks by holding a low wattage light inside. If there are any light leaks where backs fit, or film holders go in, they can usually be cured by using strips of black velvet ribbon, to take up any slackness in the fit.
If it passes all these tests, you will then have a working large format camera, which I hope will bring you a great deal of satisfaction and take some great pictures.
If you have any problems relating to this workshop section please email me for advice.
