John Davies

Technical notes for monochrome

These workshop notes are a back up to practical demonstrations. This is a guide to understanding and controlling photographic materials and equipment. The aim is to achieve negatives of the highest quality for the production of fine black and white prints. For use with both traditional wet processes and digital printing methods.

B&W film

Exposure 

Processing

spectral sensitivity

exposure basics

zone development

film speed

zone system

choice of developers

format size

controlling tones

processing guide

achieving fine grain

assessing film speed

digital

transparency exposure

quality of light

exposure guide

B&W (Panchromatic) film

Spectral sensitivity & filters

Most photographic materials are based on the chemical reaction that takes place when light reaches silver halide crystals. All modern films have silver halide emulsions suspended in gelatin which is coated onto clear acetate film. These emulsions have been modified with dyes in order to record a broad range of the visible spectrum.

Monochrome (black & white) negative materials vary in their sensitivity to differing colours of the spectrum. This has an important influence on the tonal contrast of the negative and the final print. The modern popular panchromatic B&W films, now mostly manufactured by Ilford, all have different spectral responses to light and are all much more sensitive towards the ultra violet and blue end of the spectrum than the red end.

The tonal colour balance of black and white film does not correspond with the vision of human eye-sight. Human vision is particularly sensitive to the yellow/green wavelengths of the spectrum and becomes blind beyond the violet (to ultraviolet) and deep-red (to infrared) ends of the spectrum.

Most all photographic (silver halide) materials record some ultraviolet light, which humans can not see. However, the earth's atmosphere and the glass lens filters out a large proportion of ultraviolet. The amount of ultraviolet which is recorded on the negative does vary and is dependent on the climate and the altitude. There is much more ultraviolet at higher altitudes, on mountains etc. Using ultraviolet filters and most other coloured filters over the lens will reduce the ultraviolet reaching the photographic film.

The colour sensitivity of B&W film is an important consideration if a rich tonal contrast range is required. For a general purpose filter in the landscape I would recommend a Yellow filter over the taking lens. A Yellow filter will help to correct the colour imbalance of most modern films and give a tonal range that corresponds closer to the way we perceive the tonality of colours in daylight. Such filtration is particularly important in landscape photography, with a yellow filter green vegetation achieves a richer tone and blue skies become darker to reveal cloud detail.

Other filters can be used to increase the contrast of different colours. For example, orange and red filters will make blue skies darker. A deep red filter can make daylight skies look like night, as typified in Ansel Adam's famous image of "Moon rise, Hernandez, New Mexico", made in sunlight one afternoon in October 1941.

Traditional (silver-halide) film imaging is excellent at recording light from the blue and ultraviolet end of the spectrum. But, as mentioned earlier, the glass lens acts as a filter that absorbs a proportion of UV. There are specialist cameras which use lenses made from quartz which can record a higher range of UV. "Pin-hole" cameras would also make excellent machines to record images in the ultraviolet spectrum because no lens is used to filter the UV light.

For recording images in the Infrared spectrum see digital.

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Film speed & light sensitivity  

It is important to assess the correct speed or sensitivity of the film you are using. Most film manufacturers tend to measure their materials in a laboratory and not in the varying conditions of the outside world. The manufacture's recommended speed (commonly rated as ASA or ISO) should be used as a guide. In practice, a film's speed can be a third to half a stop slower than indicated. I rate Ilford FP4 at ISO 80. A half a stop under exposure may not seem much but it can make a considerable difference in loosing important shadow detail. Increased exposure will reveal more shadow detail and therefore richer tonality in the final print. See the section on assessing film speed.

The speed or sensitivity of all film is largely controlled by the size of the silver halide crystals, referred to as grain size. The fast or very light sensitive, films have a coarser grain structure. The slower or less light sensitive films have a finer grain structure. The finer grain films can reveal a richer tonality and more detail.

However, the slower films tend to have a higher contrast than the faster films. In fact, it is very difficult to precisely control the contrast of some of the slow and very fine grain films during development.

In theory T-Max and other modern high tech B&W films answer some of the problems regarding fine grain versus speed. In practice it is very difficult to achieve negatives that will give a rich tonal range throughout the mid tones with these films. Try using different developers to the ones recommended.

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Format size  

The size of the negative can make a big difference to the quality of the image. However, the biggest is not always the best. Size for size and all things being equal, the 120 roll film can yeild sharper image detail than 35mm or 5x4in. sheet film. This is true of both colour and B&W 120 film. The 120 film has a much thinner acetate base which minimises refraction - the scattering of light between the layers of the film.

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Achieving fine grain  

With any particular film, a finer grain structure and therefore more detail and richer tonality can be achieved by controlling the exposure, processing and the choice of developer.

With B&W negatives the denser and darker parts of the negative have a larger grain structure than the thinner more transparent parts of the negative. So ensure the dense parts of the negative are minimised by not over exposing the negative and by not over developing the negative.

With colour negatives the grain pattern tends to become smaller with increased density !

It is also important to control the temperature of all the chemicals during processing and including the final wash. Slight fluctuations in temperature between the solutions will result in slight reticulation which is where the silver halide crystals form larger crystals to give the appearance of larger grain. Greater temperature fluctuations between solutions will result in a greater size of grain. In extreme cases the silver halide crystals form dominant textured patterns.

Other factors that have an impact on quality are the choice of developers, film speed and format size.

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Digital  

Most major photographic manufacturers are changing to digital imaging technology and there are many sites on the internet covering this subject. The quality of digital photo technology has rapidly improved in recent years but CCD sensors still have some way to go to compete with the versatility of the boiled cow bones that are manufactured into gelatin film. To date (2010) I have not seen anything to match the quality of a fine B&W silver gelatin print made on fibre-based paper and made from a negative.

Digital scans can be made from negatives or transparencies and then reproduced by ink-jet or 'C' type light-jet methods. Drum scans, where the film is sandwiched between special gel or oil and held in place by clear acetate film, can give the best photographic quality.

Digital image technology, CCD or CCTV, digital capture cameras, are excellent at recording light from the red and infra-red (IR) end of the spectrum. However, most modern cameras have filters over the CCD sensors to block out most of the IR to achieve an acceptable colour balance. The best cameras for recording images in the IR spectrum are those where the IR absorbtion filter can be removed, such as some of the Sigma cameras.

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Exposure

Exposure basics  

To achieve fine quality prints it is advisable to have good quality negatives that are correctly exposed and developed. It is good practice to set an exposure which takes the shadow detail into account.

A simple and common general method of making an exposure reading is to first set your light meter to the correct film speed (ISO / ASA) and then to properly assess an average mid grey area within your subject area. Exposure meters will always measure reflected light as a middle grey (18% reflectance). Light meters are designed to give "average" readings and seldom indicate an exposure compatible with the photographer's visualisation. For more exact control of negative exposure make sure you record the shadow detail - explained in zones and controlling tones .

If using a meter built in to your camera make sure you know how it functions, as modern camera exposure meters are calculated to make readings in variety of different ways. For example, some expose only for the centre of the viewfinder or are centre-weighted.

There are two types of exposure meters: the direct or reflected-light type and the incident or diffuser type. The direct exposure method is the most common and this is the type that are built in to cameras. The incident type is described in the section on transparency exposure.

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Zone System - introduction  

This guide is designed for photographers who use cameras with built-in exposure meters where the camera settings can be controlled and also those who use a hand held reflected light exposure meter. I use a modified and simplified version of the zone system for roll film use.

The zone system was developed by Ansel Adams and is based upon the basic photographic principles that, with negatives, the exposure controls the shadow detail and the development controls the contrast and the highlight details. This system gives maximum control to help pre-visualise the tonality and contrast of the finished printed image.

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Zones and controlling tones  

Imagine a normal print with a range of tones from black through to white. If we divide the various tones over a range of ten zones - each tone or zone is separated by an exposure difference of one stop. If zone 0 is totally black in the print, the mid tone or mid grey would be zone 5 and pure white would be zone 9.

The 10 zone range is based on the assumption that most photographs of a "normal" scene will not exceed a contrast range of eight stops.

This is Ansel Adams description of the zones or tones and some typical placements. I have added "f" stops next to the zones only for my examples of lens aperture control for those who use cameras with built in meters. In practice the f stops are meant to be on a sliding scale and depend on your exposure readings and your choice of aperture.

-5 f1.4 Zone 0 Total black in the print. Clearest part of the negative.

-4 f2 .. Zone 1 Slight tonality in the print. (for 35mm - 0.08 over film base fog)

-3 f2.8 Zone 2 First suggestion of texture. Representing the darkest part of the image.

-2 f4 .. Zone 3 Average shadow detail. Adequate texture.

-1 f5.6 Zone 4 Dark grey, landscape shadow, Caucasian facial shadow, dark foliage.

.0 f8 .. Zone 5 Mid grey of exposure meters. Kodak 18% grey card. Dark skin.

+1 f11 Zone 6 Average Caucasian "white" skin value in sunlight.

+2 f16 Zone 7 Very light skin. Light grey concrete.

+3 f22 Zone 8 Whites with textures. Snow in shade.

+4 f32 Zone 9 Pure white, paper base. Snow in sunlight.

I have also added + and - numbers next to each zone. These indicate the exposure (or f stop) differences from the indicted exposure meter reading. So, +1 would mean opening the lens aperture by one stop, for example from f11 to f8.

When using the camera's exposure meter, first make an exposure reading of a shadow area within the scene you want to record (zone 3). To do this, make a light reading from the shadow detail, read the values on the meter and adjust the exposure settings by -2 , by simply stopping the lens down by 2 stops from the indicted light reading. For example, if the shadow reading indicates an aperture of f4 then close the lens (by -2) to f8, to give the correct exposure. This will ensure that shadow detail is recorded onto your film.

Assessing film speed  

As mentioned in the section on light sensitivity the manufacturer's recommended speed rating should be used as a guide. To assess the effective speed of a particular film with your own particular equipment it is necessary to make a test for yourself.

If you normally work in a studio then make this test with the lights you normally use. If you work outside it is best to make the test in lighting conditions which are relatively stable.

1. Find a high contrast scene by measuring, with your exposure meter, the difference between particular light and dark areas so there is a difference of about 8 stops or zones.

2. Start by using the manufacture's recommended speed setting (ISO). Measure the exposure of the dark area where you want to see just a hint of texture in the shadows or the first suggestion of texture in the shadow detail (zone 2). Set your camera to reduce this exposure reading by 3 stops (or 3 zones). For example, if this shadow reading gave an exposure of f2.8 then close the lens (by -3) to f8.

3. Expose the film to this exposure setting. Then make a series of six other exposures by altering the speed settings on your light meter by one third. For example, if the manufacture's recommended speed setting is ISO 100, then first set the exposure meter at ISO 100. Then alter the settings to slower speeds of ISO: 80, 64 and 50 and then make three more exposures to faster speeds of ISO: 125, 160 and 200.

4. Make careful notes of the 7 exposures and then process the film in your chosen developer and remember to keep the temperature and agitation methods consistent. See processing guide.

5. When the negatives are dry place them on a light box and carefully assess which negative shows the first hint of detail in the shadow area (the shadow area you choose to calculate the exposures). The speed setting for this particular film (in association with the development and camera equipment) is measured from the negative you choose. For example, choose the negative with the zone 2 shadow detail and if this particular negative was exposed at a film speed of ISO 80 - then ISO 80 would be the speed of this particular film in combination with the equipment and chemistry you have chosen.

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Transparency exposure  

The method for exposing colour or B&W slides correctly is different from exposing negative film and finding the exact exposure is more critical with transparency. Unlike making exposure readings for the negative where it is important to base the exposure from the shadow detail, with transparency the exposure has to be calculated from the high-light or white detail. An incident light exposure reading is recommended for this. It is ideal to use a hand held exposure meter which has a diffuser attachment, this measures the incident light that falls on your subject to achieve a high-light reading. The diffuser is normally a small translucent white dome which can be attached to a hand-held meter.

The exposure method is then quite simple: point the incident exposure meter diffuser towards the camera from (the light falling on) your subject and read the settings.

If you only have a reflected light exposure meter or one built in your camera then I would suggest you take a reading of a white area where you want to see some detail or texture and set this reading on a zone 8 (or open the lens by 3 stops from the white textured meter reading). For example if the white area exposure reading indicates an aperture of f22 then open the lens (by +3) to f8.

This method can be very useful if the light levels are too low for your exposure meter to record an average reading (mid grey or zone 5) but where you can just make a reading from a white object.

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Quality of light 

In the landscape the quality of light is very variable and individuals need to assess the quality of light to suit their own requirements to create mood and atmosphere or to make dramatic or subtle images.

The climate has a dramatic effect on the quality of light in the landscape. It is worth noting that a very high contrast lighting situation can be experienced when the atmosphere is clear and the sun is at it's highest point in the sky. What is significant about this, in terms of exposure, is that there will be relatively less shadow detail with clear blue skies in sunshine than with cloudy skies in sunshine. The shadow detail may be brighter with cloudy skies than with clear skies and in some cases the exposure will need to be longer for a sunny day than a cloudy day ! The higher contrast of stark sunlight can then be controlled by (reducing) development or, as a last resort, changing paper grades when making a print.

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Exposure guide  

With experience, I have found that I do not normally need to use an exposure meter with an average Northern Europe landscape between April and October, except for the hours around sunrise and sunset or if very cloudy.

When using negative film rated at ISO 80, with a yellow filter (x2 or 1 stop) over the lens: in sunlight I set my camera to 1/30th second at f11 and is equal to the same exposure as 1/125th at f5.6. (Without the yellow filter I use 1/60th sec. at f11). Using shorter expo sure settings will often results in a loss of shadow detail.

If the weather is cloudy and bright, with the yellow filter, I set the exposure to 1/30th at f8. I would recommend that these exposure times are used in conjunction with my processing guide.

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Processing B&W film

Zone system - development  

The zone system is an ideal method for processing individual sheet negatives where exposures take account of shadow detail and the contrast (measured by the white detail required) is controlled by development times. These notes are of particular use to roll film users and should be read in conjunction with the chapter on exposure.

Film manufacturer's recommended developing times tend to give a negative of high contrast for general landscape scenes. I use development times much less than the recommended times.

If you use a particular combination of negative film and controlled development and your results consistently produce prints of an unsatisfactory contrast when using exactly the same camera and enlarger on a normal grade of paper - then alter the development times for your negatives to achieve your normal development time. If you find that you have low contrast prints on your normal paper and you have shadow detail in the negative then increase the development times when processing your film  - start by increasing the development times, initially by 10%. If, on the other hand, the contrast is too high then decrease the development times, initially by 10%.

Increase or decrease the development until you can fine tune the development times which gives the best result for you. Remember to keep the temperature and agitation methods consistent. Be careful not to use development times less than half of the manufacture's recommendation or less than 4 minutes - as even development and exact contrast control will become difficult.

This simplified zone system may seem complicated at first but practice makes it much clearer. Understanding the principles of the zone system will help you enormously when faced with varying subjects and difficult lighting situations - as it will help you to pre-visualise the tone and contrast of the finished print.

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Choice of developers  

There is a wide choice of B&W negative developers but there are two main types, characterised by the fine-grain developer and the high-acutance developer.

The fine grain developer creates a "softer" grain, where the grain structure is not as well defined and gives the appearance of a finer grain. Typical general fine grain developers are Ilford's ID 11 or Kodak's D 76 and HC-110.

The acutance developer gives a sharper grain structure by increasing the contrast between areas in the image, known as the "edge effect". The grain size and the overall contrast is more pronounced with these developers. Agfa's Rodinal is a typical acutance developer.

There is a variety of developers with combinations of these two characteristics. I use ID 11 and I dilute this developer 1 + 3. The increased dilution of the developer will increase the film's acutance.

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Processing guide                                            

The following processing guide is based on my normal development times. This produces a negative of the contrast and tone that suits my needs and takes into account the substantial contrast range found in the landscape. These times, film and chemistry can be modified later to suit your own requirements.

As a starting point you may wish to follow my technique by using Ilford's FP4 120 roll film (which I rate at ISO 80). Use Ilford ID 11 or Kodak D76 developer, dilute 1 part developer to 3 parts of distilled water. Process for 8 minutes at 21 degrees centigrade. In a day light tank, agitate the developer by one inversion of the tank every 15 seconds for the first minute and then agitate every 30 seconds for the following 2 minutes and then once every minute for the remaining 5 minutes. In the first stages of development remember to tap the bottom of the tank on the work surface after agitation to dislodge any air bubbles on the film.

For Ilford FP4 - 5x4in. sheet film, develop the film as above but increase development time to a total of 10 minutes.

Note that ID 11 developer is mixed from powder with water (I would highly recommend distilled or purified water) and needs to be left for at least 24 hours before use. The developer will oxidise if stored for long periods or if the bottles are not completely full. Oxidisation will increase the activity of the developing agents and processing times will need to be reduced.

After developing the film use a stop bath and fixative following the manufacture's recommendations. Ensure that all chemistry is exactly the same temperature including the wash rinse water. Use a fresh and non-hardening fixative for the prolonged life of negatives. Every process after the stop bath will dictate the condition and useful life of the negatives.

After washing, place the negatives in a rinse aid (wetting agent or foto-flo) diluted with distilled or purified water for about a minute, agitating the negatives a few times. Then, with the film still on the spiral-holder, shake off excess water. Use a negative squeegee or a soft "shammy" leather to carefully wipe the film and remove water droplets. I would not recommend using your fingers for this task. Removing water droplets at this stage is important to avoid drying marks.

Hang the negatives to dry in a warm and low-dust environment. Use fan assisted drying cabinets with care as circulating dust may stick to the moist gelatin film. Always handle negatives with extreme care - do not touch the surface of the negative with your fingers as moisture from the skin is often oily and acidic. When dry, place the negatives in stable acid-free negatives bags and store in a cool, dry and dark environment free from dust - this will ensure the negatives remain in good condition for a long time.

Ideally, the negatives achieved by these suggestions will produce fine grained and detailed prints that have a rich and wide tonal range. These negatives should be relatively easy to print without the need for excessive "burning in" or "dodging".

© John Davies 2010