Photographic Guidelines

Last updated: 15 May 2006
Published in: Digitising analogue media | Creating new digital media
Tags: analogue collections | cameras | photography

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Summary

There are many factors that need to be considered before and during a photographic session, this document provides a set of guidelines which will assist in planning a photographic project.

Contents

• Introduction
• The object of the exercise
• The subject
• Camera
• Lens quality
• Digital capture and sensor
• Analogue capture and film
• Processing
• Colour temperature
• Lighting
• Camera and subject supports
• Using the photos for digitisation
• Direct digital capture

Introduction

The aim of this document is to provide a set of guidelines that covers using a digital or analogue camera to photograph objects for a digitisation project. Direct digital capture with a digital camera is now the predominant method used to photograph an object however indirect analogue capture is still used where a film camera is used to photograph an object. The film is then scanned into a digital archive, an advantage of this method over the ‘born digital’ method is that you normally have an archivally stable film image in addition to the digital version.

It should be noted that much of the general advice given in these notes would be just as pertinent for setting up a direct digital capture or analogue workflow. A section at the end of these notes considers any differences in approach that working with a digital camera needs.

Direct digital capture will normally provide the best quality at the cheapest rate however there are times when indirect analogue capture can provide a better, easier or more pragmatic capture process. Reasons for this might include:

• To complete an image collection already largely completed by traditional analogue means and wanting to standardise the workflow, so all images are digitised from similar sources.
• Wishing to archive a collection of traditional film images as an analogue back up to the Digital archive. This would have the advantage of providing a further secure back up that could be reused at a later date to re-capture digital images. This can be advantageous as film transparencies are easy to store and preserve and later digitisation can take advantage of any advances in technology that might have taken place since the original capture.
• Having access to professional photo dept who are already established to capture high quality analogue images but who do not wish to, or do not have the budget to establish a digital capture capability.

This guide does not provide a set of hard-and-fast rules but rather raises awareness of issues that may have an effect on the quality of photographic images taken prior to digitisation.

Photography is a complex subject and these notes are too short to provide a complete guide to all aspects of the craft. Many original materials, such as fragile manuscripts, three dimensional works and works with highly reflective surfaces will normally require specialist knowledge and techniques. In these cases it is recommended that you find and consult with a professional photographer - if you are fortunate in having on-site Photographic Services within your host institution they may well be able to supply the necessary skills and equipment.

All in all, it should be remembered that taking photographs at a quality useful for digitisation is neither easy to undertake nor likely to be particularly cheap. It is often only practicable when there is already an established infrastructure to undertake the photography.

The object of the exercise

The main aim is to create an accurate photographic representation of the subject without significant loss of information content and without damaging the subject in the process.

Avoiding damage to the object to be photographed is normally of paramount importance. Taking that as the starting point we’ll explore some of the factors involved in trying to achieve this.

The subject

It is assumed that you have obtained the necessary permissions to take photographs of the subject(s) - preferably in writing. Items may still be in copyright. Infringement of copyright must be avoided. Failing to pay attention to copyright law could bring about withdrawal of items from the digitised collection or even prosecution. Both could be expensive.

Normally the subject has some value (otherwise why is it being photographed/digitised?) and, although there might be exceptions, it would not normally be acceptable to damage it during the photographic process. In a number of instances, e.g. ancient manuscripts, it may well be that the process has to happen with the guidance of a specialist conservator. It will be reassuring to the photographic team, if it can be arranged for the conservator to perform all necessary handling of the subject, although it should be realised that this is likely to also considerably slow down the rate of capture.

Some objects may not have any great intrinsic value but can still represent the culmination of months of work. Whatever the object and what ever its value it is always best practice to make sure that the act of photographing it does not in any way bring it to harm.

Camera

In a perfect world, the choice of the correct format would be purely dependent on how much information or detail needs to be recorded within the original. Large oil paintings with complex detail might well benefit from being photographed with a larger format such as 5×4ins. However simpler works and many 3-dimensional works will not need nearly so much detail to reliably and accurately describe them and can often be acceptably photographed with a 35mm camera. In the real world, for many digitisation projects the choice of camera will be a 35mm SLR, although this is more likely to be driven by pragmatic issues such as budget and camera availability than any quality issues.

Lens quality

Image quality will vary enormously depending on the quality of the lens(es) used and it is best not to compromise. Avoid basic ‘kit’ zoom lenses if at all possible, they are designed to give “acceptable” performance across a wide range of uses but rarely produce the image quality of a fixed focal length lens. A well manufactured prime lens from an established manufacturer of fixed focal length (i.e. not a zoom) will always create noticeably higher quality images.

Zoom lenses sometimes offer macro (close up) capability as an added ‘feature’. Again there is a compromise in image quality with such lenses. If there is a reasonable amount of macro work to be undertaken then it would be best to invest in a dedicated macro lens.

All lenses suffer from aberrations and distortion in one area or another. Computer aided design and manufacture along with the development of special glasses have reduced these faults in recent years but there is no such thing as the perfect lens. It is therefore important that you make the most of the lens’s quality.

You will find by testing that all lenses have an aperture range over which they give their best performance. It pays to get to know which aperture settings allow your lenses to perform at their best (and their worst!). Find out what this is for your lenses and try to use those settings wherever possible, for most lenses the rule of thumb is to avoid using aperture settings within two stops of either end.

Wide-angle lenses are particularly prone to curvature at the edges of the image. This fault is particularly apparent when the lens is tilted in the vertical plane (e.g. when tilting the camera backward to get the whole of the front of a building in). Flat field wide-angle lenses, perspective control lenses and specialist cameras are available but are generally more expensive than ‘standard’ equipment. It is therefore good practice to avoid using wide-angle lenses unless they are absolutely necessary to get the required photograph.

The price of a good quality lens can vary from around a hundred pounds to several thousand pounds, if a specialist or expensive lens is required for part of the digitisation it might be worth renting a lens for a short period of time.

Digital capture and sensor

The most important component in a digital camera is the sensor which is equivalent to the film in an analogue camera. Generally speaking the higher the number of sensitive pixels on the sensor (measured in megapixels) the higher the quality. However, competing manufacturers use the megapixel count as their key battle ground, this often means several million pixels are squeezed onto a very small sensor. Too many pixels squashed together in close proximity may lead to increased levels of interference or ‘noise’ and reduced image quality. Other factors which contribute to digital image quality are the physical size of the sensor, its dynamic range and the type of sensor.

Analogue capture and film

The choice of film used is the single variable most likely to affect the quality of the photographs made.

Different films will provide quite different visual results, even when from the same original. Films are often optimised for specific uses and will work well for the task for which they were intended but not necessarily for others. Designing and producing films is a matter of compromise; generally between quality and the amount of light needed to record an image. Better quality films (with higher resolution) need more light to work and are said to have a ‘slower’ speed, on the other hand ‘faster’ films will need less light but be of a lower quality (and lower resolution). Films will also be made with different colour balances and are optimised for different colour temperature light sources.

It is important that before the photography is started, research is undertaken to ascertain what film will provide the best quality results for the project. This is likely to mean undertaking some testing of a range of the possible contenders, although sometimes a photographer will already have established favourite film emulsions with which he/she is most happy.

Whichever film you settle on:

• Buy all film in one go, from the same production batch (the date and batch no is printed on all film boxes). It is best if the whole project can be photographed from the same batch of film, although film is now made sufficiently accurate to not make this an absolute necessity. It can be worth testing one roll of the proposed film before a large purchase of that batch of film is made. Make sure that the ‘Use by’ date gives sufficient time to use all the film by that date.
• It is good practice to test the purchased film by photographing colour targets and taking measurements from the processed film (keep these test images for future reference). Any required compensation for speed or colour accuracy can then be made. Don’t assume that the speed rating or the colour balance is always exactly right, although production quality is sufficiently high these days to make variations rare.
• Store all film in a cool place, a refrigerator is ideal (5-10°, but not freezing), but let it return to room temperature before removing it from the can/packet to avoid condensation on the film’s emulsion.
• Include shots of test cards (at least occasionally) to check for consistency and for use in calibration. These shots can also be kept to provide a visual record of any changes in the film or processing.
• Process as soon as possible after exposure and store in a cool, dry and dark place in the meantime.
• Once the processed film is returned, immediately check for any faults, both in the photography as well as any others caused by faulty film, processing or equipment. If any faults are found it will always be easier to re-shoot sooner rather than later.
• As soon as the film has been checked and all images sorted and edited, they should be catalogued, recording all relevant Metadata and then filed and stored under appropriate storage conditions (cool, dry and dark) ready for later digitisation.

Processing

After the choice of film the variable most likely to have an influence on the quality of the final photographs is the processing. Processing laboratories vary greatly and it is most important to find a lab that is able to provide the level of expertise, quality and consistency that you require for your project. Despite much improvement in standardisation over the last few years; film processing is based upon chemical reactions which are in continual flux (depending on temp, concentration and time) and the process is hard to absolutely standardise. Kodak (Qlab) and FujiFilm both provide testing and calibration systems that film laboratories can use to help standardise their processing. It is best to find a film laboratory that uses one of these systems and then stay with them.

Colour temperature

It is a truism in most image work-flows that ‘what goes in, comes out’; if there is to be any chance of getting accurate colour in the final digitised image, then it is imperative that the initial image is photographed with as accurate colour as possible. This means making sure that all light sources are and remain at their correct colour temperature for all photography.

The colour temperature of a light source is simply a measure of the ‘blueness’ of the light and is measured in degrees Kelvin (°K) with higher temperatures having more blue content. The range of colour temperatures runs from as low as under 2,000°K for candle light right up to over 10,000°K for the very blue light from the sky on a clear day in the mountains.

All studio lights must have their colour temperature regularly tested and if found to be outside their standard then the bulb or tube should be replaced. If this is impossible or when working with non-standard photographic lighting, then filtration can be added to the lighting or camera to correct the difference, however it is always best to work with correct lights.

Some common colour temperatures

Lighting

Without some form of lighting, it would be impossible to take any photographs at all. It is the quality and nature of the lighting which will make the photograph a success or not. Setting up lighting for photography is a skilled operation. Although a simple copy-camera lighting set-up might be relatively easy to establish; lighting a large sculpture or trying to bring out the paper texture in an ancient manuscript can be a far more complex task.

If high quality results are required then the photographer will hopefully have access to some proper lighting equipment to undertake the photography, however sometimes the photographer will have to make do with any available lights on site or other ambient lighting.

Studio lighting

Used with the necessary skills studio lighting can provide a great deal of control over the illumination of the subject. There are three main types in general use:

• Electronic flash
  Electronic flash units are the standard lighting tool of the professional photographer. They are often lightweight, generally portable, are powerful, with a variable power output but do not need lots of mains power to drive them. They have a constant colour temperature (equivalent to a ‘standard’ daylight) and a low thermal (working) temperature. The ‘flash’ provides a large amount of light in a very small time period allowing relatively fast exposures, which helps in photographing any moving objects. The ‘flash’ is also not long enough to allow any heat or excess light build up that could damage items such as paintings or documents.
  
  Although larger and more powerful flash units are expensive, smaller units are now available at prices to fit most budgets. Because flash lighting only takes a split second, flash units normally also have a tungsten ‘modelling’ light to provide some visual indication of how the flash lighting will look. This is only approximate and one problem of using flash is that the actual lighting the camera ‘sees’ might well be different from what the photographer sees when setting up the shot. For this reason flash tends to be used with various brollies, light-boxes and other ‘light shapers’ to soften the lighting. It is also why it is normal for photographers to check their lighting with instant films (like Polaroid) before exposure.
• Tungsten and HMI
  Continuous light sources such as Tungsten and HMI (Hydrargyrum, Medium Arc, Iodine) are the traditional light source used in the photographic studio. The main advantage of these lights is that you can see what the lighting is actually doing before you take the shot. Both Tungsten and HMI lights are preferred by photographers who wish to use a harder light source to bring out the surface texture of the original. This lighting technique, called ‘raking light’ can provide surface detail that is quite invisible under softer flash lighting.
  
  There are a few problems with using Tungsten lights (some of which are addressed by the more modern alternative - HMI). The first is that tungsten lights use a lot of power, producing a lot of heat, and by necessity a lot of light energy, which can cause conservation problems for many originals that should be kept away from heat or excessive light which may damage them. The second problem is that tungsten lights are a much warmer (redder) colour and need special films or filters to be able to produce accurate colour. This colour temperature is also found to change as the lighting ages and therefore needs consistent checking during the life of the light. This is not an issue for digital cameras which can be white balanced to work under most common types of lighting.
  
  HMI lights are the modern equivalent of the original arc-lights used in searchlights and on early film sets. They address many of the inherent problems of Tungsten, their colour temperature is standardised at daylight and they produce much less heat. However they are very expensive to purchase and run and the bulbs, although very expensive, still suffer from wandering colour temperature as they get older and must therefore be regularly checked and changed when necessary.
• Fluorescent and other ‘cold’ lights
  Fluorescent lighting for the studio has only recently become available to the professional photographer. It is of particular interest to the copy photographer working with delicate and valuable originals. Although limited spectrum fluorescent lighting has been in the office for many years, it is only recently that fluorescent bulbs have been available that can provide an accurate, balanced and full spectrum light source. These lights are used in banks and therefore inherently provide a soft light and can not create a ‘raking light’ shot. Their big advantage is that they produce very little heat, but a relatively high light output. They also provide a very specific range of the spectrum with only very small amounts of Infrared and Ultraviolet radiation.

Non-studio and ambient lighting

Without calibrated studio lighting the photographer will find it much harder to take photos to an acceptable, reliable and consistent level of quality. However with a little ingenuity and care, it can be quite possible to use other non-photographic lighting, with the one proviso that it becomes harder to be able to provide any consistency of lighting or approach.

This can be acceptable if the photos are each unique images, but if they are part of a set or collection then it is important that all the images have a close visual appearance with consistent lighting and background.

When taking photographs with non-standardised lights, it should be considered that they will not have been made to a standard colour temperature and it is therefore important to measure the colour temperature of the light source with a colour temperature meter. Any mismatch between the colour temp of the film and the light source can be corrected by using colour correction (CC) filters over either the lighting or the camera lens. For instance a bluish filter (an 80B CC filter) can be used to cool the reddish colour of a tungsten light from 3,200°K to standard daylight at 6,500°K.

All in all, the skill needed to gain good and reliable results from non-standard lighting would most probably make it a task for the professional photographer. When it is considered that the ‘colour temperature’ meter needed to work in this way can easily cost as much as a cheap flash lighting kit, it might seem to make more sense to just invest in some proper (but simple) lighting equipment in the first place.

If it is necessary to work with non-standardised and ambient lights then these hints will help:

• Standardise on one light source, don’t mix types of light, either work with daylight and turn off the tungsten lighting, or use the tungsten and cut off any daylight.
• Avoid using any fluorescent lights at all. Only photographic quality fluorescent tubes can be safely used for photography, others can often have incomplete spectra with some parts of the colour spectrum entirely missing.
• It is not only the lighting that can affect the overall colour, avoid working near to any coloured walls or anything else that might reflect an unwanted caste of light over the subject.
• Remember that the colour of daylight will vary throughout the day from the warm light around sunrise and sunset to the cooler colour of midday. Cloud cover can also affect the colour temperature of the light.

Camera and subject supports

One of the easiest ways to compromise the quality of images, as well as possibly damaging any material/subject is to not securely hold both the camera and the object whilst they are being photographed.

It is imperative that the camera is held absolutely still and stable whilst it is being used. Any movement during exposure will markedly damage the image quality. This is therefore an area where it is normally unproductive to try and skimp in specifications.

Camera stands and other supports are often surprisingly expensive. They need to be heavy to be effective and well engineered to be easy and safe to use. The correct type of stand will depend entirely on the modality of what is being photographed. You will need a different stand to hold the camera vertically above a flat artwork to that which you use to photograph a large sculpture. Common camera stands include ‘copy stands’ that allow both the height of camera and base to be adjusted vertically to heavy ‘studio stands’ for use in the studio and lighter tripods for use outside the studio.

The best efforts of the sturdiest tripod will come to nothing if it is standing on an unstable floor - make sure that any room being used for the photography has firm flooring. If the photography has to take place in a room with an unsteady floor then attempt to minimise movement during exposure by not allowing any movement near the camera whilst it is being used.

It is not only the camera that must be kept perfectly still, it is also important that the subject is kept both still and also totally safe and secure. Subject stands will again vary and be entirely dependent upon what they have been made to hold. Some smaller 2D works can be happily (and safely) laid flat on the copy stand whilst larger paintings will be safe placed on a large easel. However some items such as old and delicate books will need substantial systems to protect and support them. These are best designed (and possibly operated) by specialised conservators with knowledge of the specific books being photographed. Sometimes these are quite simple devices, but they can also be very substantial and complicated with price tags to match.

While it is essential that a camera is securely supported, thought should also be given to anything attached or connected to the camera, a poorly attached cable release, synch lead, lens hood, lens cap, or even worse, lens can do considerable damage if it falls free from the camera.

Using the photos for digitisation

Of course, once this amount of effort has gone into obtaining good photographic images, it is worth ensuring that all this work is not compromised by poor digitisation. These issues are covered, in full, in other JISC Digital Media documents such as Scanners and Basic Guidelines for Image Capture and Optimisation.

Direct digital capture

These notes have been written primarily to help the project intending to photograph works and then digitise them using an indirect analogue capture workflow. However much of the advice given here for photography will still be quite accurate for the project that is using a digital camera within a direct digital capture workflow.

In general operation you will find that the digital camera works in much the same way as the film camera, although due to its relatively small ‘image capture area’ it tends to be even fussier about the quality of all parts of the imaging chain.

• Film: Instead of choosing a film format it will be the ‘capture resolution’ and digital camera type (scanning, 3-shot, matrix) that quantifies the size and quality of the image data that is caught by the camera. Just like with film, the digital camera will find it easier to create a high quality image from more light, rather than less.
• Lenses: The digital camera will still need a lens and all the quality issues discussed above will be just as relevant for the digital camera as for the traditional film one. Indeed the resolving power of many digital camera CCDs is equal to the finest of films and this can make the choice of lens acutely important.
• Lighting: The lighting chosen for use with a digital camera is a more difficult and specialised choice and will be dependent upon the choice of camera. Some cameras will only work with one or another type of lighting, for instance it is impossible to use flash lighting with a camera using a ‘scanning back’ as the exposure can take many seconds (or even minutes) to undertake. However the 3-shot and the 1-shot ‘matrix’ camera will work well with flash. Both fluorescent and HMI lights are popular for use with digital cameras.
• Colour temperature: The principle of colour temperature is of course identical with both film and digital cameras and the digital camera is able to work with a wide range of colour temperatures. This is due to the way in which the digital camera is calibrated to grey under the shooting lights each time that the camera is set up before use. This process is often called either checking white balance or ‘doing the greys’ and means that whatever the colour temperature of the shooting light, the camera is calibrated to it before shooting.
• Film and processing: There is of course no film or processing involved in the direct digital capture workflow, but do not forget that all images will still need to be checked and processed before being signed off. See JISC Digital Media’s advice on Basic Guidelines for Image Capture and Optimisation.

You can read more about digital cameras and their use in other JISC Digital Media documents: Digital Cameras, The Digital SLR Camera for Teaching, Learning and Digitisation and Using a Budget Digital Camera for Teaching, Learning and Research.

Last updated: 15 May 2006
Published in: Digitising analogue media | Creating new digital media
Tags: analogue collections | cameras | photography

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