On using an old camera - and why you might even care

Contents:

Introduction

Using totally manual cameras did much to teach me the basic theory and nomenclature of photography in a way that I think might prove difficult with a modern, "auto everything" device. Of course, it could be argued that it is not necessary to have this level of understanding, but I thought I would explain the process of using such a camera, and what I learned as a result.

The basics

A basic camera

Fig 1. Diagram of a simple camera

The camera is a box containing a light sensitive material and a device for allowing light to shine on that material. This device is usually a lens, but in the simplest form it can be a small pin hole. To take a photograph, the camera is pointed at the subject and light coming from the subject is allowed to pass through the device to produce an image of the subject on the material. In order that the image produced is an accurate representation of the subject the correct amount of light must hit the material. If not the subject will appear either too dull or too bright.

There are a couple of factors affecting the amount of the available light required to reproduce the image (the "correct exposure"):

  • The sensitivity of the light sensitive material.
  • The amount of light coming from the subject - usually related to the amount of light shining on it, unless for example the subject is in fact a lamp.

Given a set of conditions for the amount of available light and the sensitivity of the material, the correct exposure for these conditions is achieved by controlling two factors within the camera:

  • The amount of light allowed through by the device. In the case of the pin-hole camera, not very much, hence the use of lenses.
  • The length of time that light is allowed in.

To be more specific (and technical)

At this point it might be useful to introduce a few technical terms used to define the factors described above, before explaining them in more detail:

  • Films and cameras are available in a variety of sizes and formats.
  • The sensitivity of the material is usually termed "film speed".
  • Exposure control for a manual camera would be achieved by setting an "aperture" and a "shutter speed".
  • The magnification factor of a given lens is expressed in terms of its "focal length".

Film sizes and formats

Over the years there have been, and probably still are, a large number of film sizes and formats (most of them introduced by Kodak, I think!) so this is a sample:

By far the most popular film size now is 35mm, conventionally giving an image size of 36x24mm. Before switching to digital photography, all the cameras I used took this type of film. As an aside, the majority I used were of a type called "Single Lens Reflex" (SLR). A camera of this type uses one lens both to take the photograph and to produce an image in the viewfinder, to allow both focusing and composition.

Pentax MX

Fig 2. 35mm manual SLR camera, a Pentax MX

Before the advent of the 35mm camera most cameras were "roll-film" cameras. Although there were a number of different sizes the most common, and the one which survives today, is "120" (there is also "220", the same width but twice the length, for twice as many pictures per roll). This will allow an image 6cm high (or 2¼ inches). From this a number of different formats can be derived, commonly 6x4.5, 6x6, 6x7 or 6x9cm. Some cameras came with masks for more than one format.

APS, a smaller format than 35mm, was introduced in the 1980s but has been somewhat overtaken by digital technology. Some digital cameras use a sensor the size as this and are sometimes referred to as APS format.

Film speed

Films are available in a variety of sensitivities or "speeds". These are defined by an international standard (ISO), which is in turn based on an American standard (ASA). In fact it is this standard that is often used to describe a film in conversation - or more usually in arguments - between photographers.

A film of average sensitivity would be marked as ISO 100 or 100 ASA. Films marked 200 ASA, 400 ASA, 800 ASA etc. would be "faster", each being twice as sensitive as the previous one as reflected in the values. "Slower" films are also available. Broadly speaking the slower the film the finer the detail it can record and that is usually the reason for picking a slower film over a faster one.

Aperture

For any given lens there is a maximum amount of light that it can let through, and this amount will vary from one lens to another. However, most are fitted with a diaphragm (also called an iris), which can be used to reduce the amount of light passed through by varying the size of the "aperture". The size of the aperture is defined in terms of a number in a (fairly) standard series:

1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32

These are known as ƒ-numbers, ƒ-stops or simply stops. For each step (or stop) in the series the amount of light allowed through is halved. Note that this does not follow the rule for film speeds in that the numbers themselves are not doubling for each step in the sequence. When written, these numbers are expressed as a ratio, 1:[the number] or as ƒ/[the number], although verbally they would be referred to simply as, "f" whatever. ƒ/16 is "smaller" than ƒ/11 because it represents a smaller hole, letting in less light.

A lens might have a maximum aperture of, say, ƒ/2, and allow the setting of any aperture from ƒ/2 to, say, ƒ/16. Speed is also sometimes used to describe apertures, especially maximum apertures, and a lens with maximum of ƒ/1.4 would be regarded as "faster" than the ƒ/2 lens. For the record, the vast majoriry of lenses have a maximum aperture smaller than ƒ/1.

Lens aperture ring

Fig 3. Lens aperture ring, showing ƒ-numbers 2 - 16 and ƒ/5.6 selected.

Lens aperture f2

Fig 4. ƒ/2,

Lens aperture f2.8

ƒ/2.8,

Lens aperture f4

ƒ/4...

Lens aperture f16

...and ƒ/16 (Camera back removed and no film!)

Some lenses will also allow the selection of half-stops, positions between the numbers. These allow for more precise control but are typically not marked on the aperture ring.

Shutter speed

In the early days of photography the materials used to capture the image were not very sensitive (and lenses not very fast) so long exposure times were required. This could be controlled by simply removing a light-tight cap from the front of the lens for a duration timed by a watch. When films became faster a more precise method was required to provide shorter exposure times and the "shutter" was introduced, which was designed to open and then shut again after a controllable interval.

The settings for these intervals are known as "shutter speeds". Some early cameras used a different set of intervals but the standard would be something like:

One second, half a second, quarter of a second, 1/8 of a second, 1/15 of a second, 1/30 of a second, 1/60 of a second, 1/125 of a second, 1/250 of a second, 1/500 of a second, 1/1000 of a second.

Again, each setting is half that of the previous one, approximately at least. These would usually be marked on the camera as 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000.

Shutter speed dial

Fig 5. Shutter speed dial, 1 - 1/1000 of a second, 1/1000 sec selected

Focal length

To over simplify somewhat, the focal length of a lens is the distance between the lens and the film required to produce a focused image and for photographic lenses this is traditionally measured in millimetres. Because of the way that light from the image is focused by the lens onto the film then the longer the focal length then the larger the resulting image. Again there is a doubling relationship involved, a lens with a focal length of 200mm will produce an image twice the size of one with a 100mm focal length. Lenses are described as "long" or "short" focal length. Short lenses are also known as "wide-angle", long lenses as "telephoto". Between these lies the "standard" lens, which has a focal length approximately the same as the diagonal width of the film used. For 35mm cameras a 50mm lens is generally accepted as standard, despite being a bit "long". The commonly used term "zoom" describes a lens that will operate over a continuous range of focal lengths. They can also be classified as wide-angle, standard or telephoto, depending on the range provided.

Focal length and its effect on aperture size

All lenses, regardless of focal length, will be likely to allow the setting of a similar range of apertures, as defined by the ƒ-numbers described above, but physical size of an aperture for a given ƒ-number will increase with focal length. This has implications that are explained later.

Strictly optional notes on focal length

For the record, the focal length is the distance required to focus on a distant subject (at so-called infinity). The lens-film distance will increase when focusing on closer subjects. Also, it is the distance from the film to the "optical centre" of the lens which is measured, and with modern compound lenses with many separate pieces of glass and/or plastic making up the lens it can be almost anywhere and is usually outside the lens itself. For instance, a "long" lens will probably be more compact than its focal length suggests (for the pedants, this is the true meaning of telephoto).

Putting it all together

A rule of thumb

There is a rule of thumb, sometimes called the ƒ/16 rule, which states that in sunny conditions the correct exposure for a photograph can be achieved by setting the aperture to ƒ/16 and the shutter speed to one over the film speed, or the closest match. Assuming a film speed of 100 ASA this would be 1/125 of a second, as the closest match. For a 200 ASA film, it would be 1/250 of a second, which is half as long, because the film is twice as sensitive.

Other methods

This may no longer be true but it used to be the case that films came with a chart, either on the box or on a leaflet, which showed the recommended exposure for different conditions from sunshine to heavy cloud. One famous photographer claimed to have achieved good results simply by following the chart but most people preferred to use an exposure meter.

The exposure meter

This is a device, either built into the camera or separate, which measures the amount of available light in order to provide a recommended exposure. It is thus extremely useful, especially if you understand the basis on which it is operating.

It is unable to picture the scene and judge which objects should be dark and which pale, so it measures the reflected light in total and takes that to be a suitable average. But many objects will reflect more or less light than average and if either predominates then this will skew the reading. A white cat on a pale background and a black cat on a dark background would both come out as grey (or "under" and "over" exposed respectively) if the recommended exposure were used. There is also a problem sometimes with readings taken in duller conditions, where the sky is very much brighter than the ground, which can lead to under exposure.

As long as this is understood then a correction based on judgment can be applied or a reading taken from a more averagely reflective subject, such as a stone wall, in the same lighting conditions.

For more sophisticated measurement, and for those with money to spend, a "spot meter" could be used to sample the light from a small area of the subject, or indeed several separate areas of the subject, to arrive at a correct exposure.

Different aperture/shutter speed combinations, and why

Apertures and shutter speeds are designed work on the principle of halving or doubling the amount of light allowed between each value in the series, so all the following would give the correct exposure for a sunlight scene taken using 100 ASA film:

1/1000 sec at ƒ/5.6 , 1/500 sec at ƒ/8, 1/250 sec at ƒ/11, 1/125 sec at ƒ/16, 1/60 sec at ƒ/22.

"Why then," you might ask, "should I choose one combination over another?" and unfortunately the answer is, "it depends..."

Starting with what I think is relatively easy to explain and understand, one factor is the amount of movement occurring in the subject and how that is captured. To "freeze" rapid action, use a fast shutter speed like 1/1000 of a second. To produce a picture of a subject moving against a blurred background, choose a slower speed and follow the subject (or "pan") as you take the picture – and be prepared try it more than once!

Another factor is the focal length of the lens being used, and hence its degree of magnification. Assuming that the camera is being hand held then it is likely to move around slightly while the photograph is taken, which may result in a blurred image (called "camera shake"). The likelihood of this increases as the exposure time increases (since it is moving around for longer) and as the degree of magnification increases (since this magnifies the effect of the movement). It is generally thought that the slowest safe shutter speed for hand holding is one over the focal length, or the closest match. For a 100mm lens, this would be 1/125 of a second, so the last combination above would not be wise, unless you were trying the panning option.

When it comes to choosing an aperture setting then the first point to remember is that few lenses give their best performance at their maximum aperture (this will involve using the whole lens area, and hence all its flaws) so if possible it is a good idea to "stop it down" a bit – select a smaller aperture.

You might, however, want to select a particular aperture for an effect that is less easy to explain. There is a term called "depth of field", which is used to describe the range of objects that are in focus in an image, from the furthest to the nearest and this range increases as the aperture gets smaller. So, if you want to take a photograph of a subject in front of a distracting background, you would select a larger aperture to blur the distraction, whereas you would use a smaller aperture for scenes with, say, a gate in the foreground and distant hills.

Lens aperture f4

28mm lens atƒ/4 (on APS format digital camera)

Lens aperture f4

...at ƒ/8

Lens aperture f4

...and at ƒ/16

The depth of field is a function of the physical size of the aperture (the smaller the hole, the greater the depth of field), which as previously mentioned increases with focal length. This means that a wide-angle lens, with its short focal length and small physical apertures will give a greater depth of field for a given ƒ-number than a standard lens. It also means that the smaller the film format, and hence the shorter the focal length of a standard lens, then the greater the depth-of-field that is achievable.

Automatic exposure

Automatic cameras have been around for many years in a variety of forms with ever increasing sophistication. For many years the most common form of automatic exposure control (for 35mm SLRs at least) was one called "Aperture Priority". On a camera of this type, the aperture was selected by the photographer and the camera set the appropriate shutter speed, based on the reading from a built-in meter. Some other cameras used the opposite approach, called "Shutter Priority" and some even allowed a choice between the two. This meant that the operator could fix whichever was the more important setting, depending on the nature of the subject. Aperture priority would probably be used for landscapes and shutter priority for action photography.

Some later cameras had a "Program" mode, where both aperture and shutter speed were selected by the camera, from a set of pre-determined (or programmed) combinations ,providing the best compromise for the level of light. Some camers, termed "multi-mode" offered all three options along with a full manual override. Later still, cameras were made available with more than one program mode, with a bias towards smaller apertures (typically called a "scenic" or "landscape" mode) or faster shutter speeds ("sports" mode) whilst still varying the other as required.

All of these were based on the meter reading as described above, so the same issues existed regarding the accuracy of that reading. Two mechanisms were commonly provided to modify the exposure selected from the meter reading. The first, called "Exposure compensation", gave the ability simply to increase or decrease the exposure, usually to between +2 and -2 stops, in half or one third stop increments. On older cameras this would be done via a dial, usually linked to the film speed setting, where it would be used to "fool" the camera into thinking that the film required more or less light depending on the setting.
The other mechanism, known as an "Exposure lock" or "AE lock", allowed the exposure to be fixed when the camera was pointing to something other than the exact subject to be taken. This could be used, for example, to overcome the problem of dull conditions by pointing the camera more towards the ground, to lessen the effect of the relatively bright sky.

Some later cameras also came with more sophisticated metering systems which divide the image into several sections and compare the contrast between them to come up with a better estimate than could be achieved by just averaging the total. Some even include a spot metering option.

And the relevance?

Assuming you are using a modern, probably a digital, camera then most of the process is likely to be hidden from you, at least in normal operation. How much you can interfere will vary from camera to camera, and broadly the level of control available will increase with price, but it is likely that it will at least have either exposure compensation (although it may be buried deep in the menu system) or an exposure lock (typically half pressure on the shutter release will fix the exposure – try it and see). More expensive cameras may have the range of program modes as described above, or even full control of aperture and or shutter speed. Look in the manual for the terms listed above or search on the web for a specification summary that includes a list of exposure modes, then look for the letters M (manual), S (shutter priority), A (aperture priority) and P (program).

Conclusion

If your camera has any of these features then you can have a play around with them and try out the effects - before in all probability going back to the automatic mode for most of the time. But if you cannot adjust anything then just remember that the people who make these things these days are pretty clever, so the camera will usually get it right anyway (and a photo editor can often rescue the ones that need adjustment). At least now you should have an idea about what it is doing.