These things happen inside your camera when you focus, set exposure and click the shutter.
A camera is considered to be a delicate instrument but reality is they can take lots of hard work. They don’t like, being dropped, exposed to liquid, left in the sun, left unused for extended periods or stored in damp places. Treat them kndly paying some attention to these requirements and your camera will last for decades. A word of caution here about DIY camera repairs. Minor exterior cleaning is possible provided you have knowledge of the material you are cleaning and the cleaning method, but, mechanical and/or electronic repairs are likely to cause irretrievable damage unless you are very experienced and have the right tools. Definitely remember - oil is the enemy.
Let's take a look at what goes on inside your camera when you decide to shoot a frame. Composing the frame is the aethsetic component, setting aperture and shutter speed, deciding on the focal point, focusing and releasing the shutter are actions which follow each other in that order. It’s interesting to note the names given to these camera controls. Aperture we can agree with, being a name for an opening, which it is, but shutter speed, not so much as this camera control is actually how long the shutter remains open, admitting light – bulb setting is manually controlled time, 1/250th of a second is a common bright daylight setting. So, in our opinion shutter time would be more appropriate, but shutter speed it is and has been for over a century.
Every photographer wants their frames to be sharp so here we come to the sharp end of the camera – focus. Zone focus, manual focus and auto focus. Step one is to identify the main subject of the frame. This decision will have bearing on aperture and shutter speed as well, in as much as depth of field (the in focus part of the frame) is playing a part and there is opportunity for a nice soft blurred background ‘bokeh’ - a shallow depth of field using a larger aperture. A close up portrait perhaps or a still life composition. A landscape scenic shot on infinity focus and a small aperture gives the frame crisp sharpness front to back. Zone focusing cameras such as the Olympus Trip 35, Rollei's tiny T and SE, Voigtlanders Perkeo II medium format and many others from the 1950s/60s have very simple focusing - closeup, middle distance and infinity. Best to shoot these cameras on an aperture of F8 to F10 thereby mostly ensuring sharp focus. Manual focusing rangefinders from the 1970s/80s - Canonet GIII-QL17, Minolta 7SII, Olympus RC and SP - use a coinicident image system viewed through the viewfinder which shows a double image usually in a yellow patch central in the view window. Turning the fixed lens focusing ring brings the double image together as a single image – focus achieved. Many SLR (single lens reflex) cameras from the 1980s/90s, - Nikon F80, F4, Pentax 645 both 35mm and medium format, whilst still able to use manual focus lenses have a focus confirming dot which lights in the viewfinder when subject focus is achieved. A confidently easy system for the photographer. Other SLRs from this era - Pentax K1000, Olympus OM-1, Canon FTb - use a split image vertical alignment which brings the misaligned image into sharp focus as the lens focus ring is adjusted. Using auto focus lenses requires a camera body able to communicate with the lens. The lens focusing is driven either from a body mounted electronic motor or in much later gear, an ultra sonic lens mounted motor. All the major camera manufacturers are masters of auto focus. Nikon, as an example with which we are quite familiar has developed excellent auto focusing with centre focusing and a 3 D matrix system which constantly samples the frame until focus is locked by a light press on the shutter button. On these cameras the auto focus can be overridden allowing creative work with portrait, food and macro photography.
Your film camera has 3 light controls. Film Speed (Din or ASA). Din ratings date from the 1930s, largely being superseded by the ASA system from the 1950s. The current ISO standard for denoting film speed corresponds with the earlier ASA system.Aperture size and shutter speed. Film speed is the measure of the film’s light sensitivity. Generally lower ASA denoted films will produce a smoother grain than those with higher ratings, called fast film. The film speed, in vintage cameras is set via a control on the camera, either on the top plate or around the lens. Once you have loaded your film and set the film speed this should not be altered until a new film is loaded which may have a different speed rating. More recently manufactured analogue cameras – mid 1980s on usually have DX coding which reads the film speed from DX coded film automatically on loading. Film is chosen for the results it produces and the shooting situation. For instance, low light scenarios require faster (higher ASA) film. Setting the aperture or f stop is part of 3 step light control. The main point to remember is the larger the f stop number, the smaller the aperture. F16 and F22 are usually the smallest apertures on most rangefinder vintage cameras. The largest aperture (smallest aperture number) could be F1.7. At this aperture the lens is wide open admitting maximum light onto the film. As the aperture ring on the lens housing is turned the iris diaphragm within the lens opens and closes accordingly. You will be considering the scene being shot and deciding how you want the final image to look. The exposure has to be correct otherwise the frame will be over or underexposed, but firstly we must consider the subject. Shutter speed has an important role, ensuring image sharpness with fast moving subjects where maximum shutter speed is needed to freeze motion or on the other hand for some dramatic night scenes – headlight ribbons and such like, shooting off a tripod using the slowest shutter or even bulb setting (shutter open until manually closed) and employing a small aperture, F11 or smaller. Is it a portrait, a single focus nature shot or a wider angle landscape. If a portrait then a large aperture, F2 – F5.6 will allow the portrait subject to be in sharp focus and the background beyond the subject to be softly blurred, a photographic phenomena known as bokeh. Under bright conditions this type of shot will require a fast shutter speed to compensate for the wide aperture allowing the frame to be correctly exposed. Some lenses render a pleasingly soft bokeh whereas others have limited bokeh abilities. When assessing lenses for this purpose, careful consideration and research is key.
For most frames we want the subject to be in sharp, crisp focus. Shooting a frame at aperture F10 or smaller generally ensures your frame will be in focus front to back. This means the image has good depth of field. For example – landscape scenes shot on infinity focus, provided a small aperture has been selected (F10 or smaller), will be in crisp focus foreground to background. For another example – shooting wild flowers in the foreground against a distant but bright background use a larger aperture (F5.6) and a faster shutter (1/1000 or faster). Most early rangefinders max out at 1/500 which if used to shoot this particular scene would result in gross over exposure. A lens filter (lens filters) could help correct this, but for these difficult shooting situations it is better to select a camera with a fast shutter capability such as a Contax G2 (1/4000) or a Nikon F4 (1/8000). There are many other cameras with fast shutters, but usually 1/2000th is the limit. Lens filters play an important role in certain photography situations but, where at all possible it is better practice to minimise the glass placed between nature and film.