Check and Adjust Focus of a Vintage Rollfilm Camera
I describe here a simple method of checking the focus of a vintage rollfilm camera. If the camera has front lens focussing, then there is a straight forward procedure to adjust the focus.
Check the focus accuracy
The first job is to get some translucent material to act as the screen in lieu of the film. A translucent 'film' can be made easily from waxed paper. Some people use ground glass but that is not necessary. If ground glass is used, make sure the 'ground' part rests on the film runners.
Put the translucent 'film' in the camera. Tighten it by winding the take-up spool. Make sure the film is resting on the film runners. Select the widest aperture. This gives a narrow depth of field so increases accuracy. Put the camera in 'T' mode to keep the shutter open. If the camera only has 'B' mode then you will need a locking shutter release cable or have someone holding the shutter release button down while you work. Adjust the focus to infinity and aim the camera towards a distant subject. Check that the image on the screen is in focus. You may like to use a magnifying glass.
Adjust the focus to the closest value and aim the camera towards a close target subject. Again make sure that the widest aperture is selected. Move the camera backwards and forwards until the target is in focus. Use a tape measure to check that the focus distance and the distance shown on the camera's distance scale agree.
Fixed focus cameras
For fixed focus cameras, point the camera at a scene with a range of subject distances. Look for the closest item and the furthest item in focus to determine the depth of field. You can then make sure that your subject is within this range when you come to use the camera.
Adjusting Focus on Front Focussing CameraS
with front focussing
The following only really applies to front focusing vintage cameras, for example, the Kodak Junior 620, the Balda Juwella 4.5, the Ilford Craftsman and the Agfa Billy Compur and many others. In each of these cameras, the front lens screws in and out to affect focus. The distance scale is held in position by three tiny grub screws. These screw can be loosened to change the position of the scale relative to the lens position.
It may be necessary to adjust the focus scale if it has slipped or the lenses were dismounted to clean and the distance scale hadn't been put back in the correct position.
Start with adjusting the front lens so that it focusses on infinity on the wax screen. Loosen the grub screws and move the distance scale until it indicates infinity. Now tighten the grub screws. Do not remove the grub screws completely because they are tiny and difficult to get back in, and there is a big chance of them being lost. There are usually larger screws that are used as end stops. Do not loosen these. It may be necessary to turn the lens further than infinity as originally shown on the scale. To do this, loosen the grubs, turn the distance scale a bit towards a shorter distance without the lens moving, then retighten. Move the scale back to infinity. Continue to adjust until a distant subject is focussed on the screen when the camera indicates infinity.
Next check the focus at other distances. However, if it is correct at infinity it is a pretty good bet that other distances will be OK.