Photography of Cultural Heritage items

Transcription

1 Photography of Cultural Heritage items A lot of people only get to know art pieces through photographic reproductions. Nowadays with digital imaging far more common than traditional analogue photography, the visual aspect has become more emphasised than verbal communication. Cultural Heritage environments tend to offer three things at once: the picture, the image and the story. The gap between an amateurish approach and a professional one, is reflected within an image's or a text's quality. 1

2 Cultural Heritage items Heritage, art items consist of 2D or 3D originals. For 2D originals, whether it is a document, a drawing or a painting that is concerned, any photographic replica should match the original both in colour and detail as closely as possible. One of the key requirements is a high resolution, which also depends on the original's size. The higher the resolution, the better both the colour information and the colour depth. In the case of black-and-white originals, there is another key requirement: colour rendition. Very few documents are perfectly black and white. For 3D originals, e.g. architecture, interiors or outside, historic site, the approach is totally different. One of the key elements here is artificial lighting, which allows for high quality pictures of sculptures, objects and archaeological pieces. 2

3 Making good photographs: be a photographer yourself Nowadays most cameras are digital ones. A photographic camera consists of 3 parts: a dark box, a lens, and a film or sensor (to capture the incoming light). Further on there is a view finder (or screen) to compose your picture, a shutter (mechanical or electronic), and numerous gadgets. One can distinguish several groups/levels/type of camera, depending on budget as well as on the desired quality level: - the small compact: cheap, useful only for rapid shooting - system cameras: with fixed or interchangeable lens, reflex (DSLR) or electronic finder, small sensor (APS) up to "full size" 24x36mm - Medium format: best in quality but very expensive (from up to ) (30 x 45mm, 36 x 48mm, many variants): most camera systems (Leaf/Mamiya/Sinar/Alpa/ArcaSwiss/Silvestri/Cambo) make use of an interchangeable "digital back", Pentax and Leica S have a fixed sensor. - A camera can be configured using only has a few adjustments, parameters: composing, focusing, exposure dose by time and (lens) diaphragm (similar to a human eye's iris). - Though manual setting is advisable, even necessary, for all quality, studio, reproduction work, most cameras have automatic exposure systems. 3

4 Technique/lighting. Most photography of architecture, interior, exterior, sites, is done with existing natural light. For other purposes, objects, painting, document, painting, to obtain good quality it is advised to use a controllable lighting system. The first option is "continuous" light such as bulb, led, tube. One thing to ensure, when using such a system, is that the room, "studio" can be darkened. Another very useful controllable lighting system is using flash, making one completely independent of ambient light. In general there are two types of artificial studio light: diffuse (big reflector/softbox) and direct (small reflector). Diffuse lighting is best for objects, sculptures and some kind of documents (miniatures, parchment). Direct lighting is required for purely reproductive work, such as documents, paintings, drawings. Often when photographing paintings, it's advisable to use double polarization filter, this means a polarization filter on both the lens as the on the lighting system. This technique allows for elimination of most of a painting's surface reflections. When photographing sculpture, the position of the camera depends on the sculpture's size, so that the spectator can have a sensation of its dimensions: a small sculpture would be photographed from a higher position, whereas a sculpture of 80cm - 100cm would be photographed mid size. 4

5 Technique/digital image file treatment. There are two ways to get a picture: directly from the camera or you develop yourself from the RAW file. Pictures produced by the camera (computer) are typically in a compressed file format JPEG. These compressed file formats restrict making colour or other corrections afterwards. On the other hand developing yourself from RAW file is the better way to proceed: a RAW file contains all information captured by the sensor. For all quality work it is advisable to use a (stable) tripod and low ISO setting (ISO ). Technique/White balance/colour temperature. Continuous light, as daylight, can change in colour: it can be warmer or cooler. Hence the balance between red and blue changes, from a warmer to a colder sensation. Developing from RAW is by far the better way to fine tune white balance. Often a change in green/magenta is necessary (e.g. fluorescent tube). Technique exposure/histogram On most cameras an "histogram" can be made visible: It is a graph showing the distribution of the light captured by the sensor. This is very useful for controlling the exposure. 5

6 Technique image size/dimensions/resolution. There is a lot of confusion about the use/setting of size, dimension, resolution. The real size of a picture file is the amount of pixels, points, dots it has. The higher the amount of pixels, the higher the absolute resolution. On the other hand a picture file can be exported in a different document size, i.e. a same picture with the same quality, can be exported at different dimensions, with different resolutions: e.g. a picture at 300dpi width 30cm (quality print resolution), has the same quality as that picture at 125cm at 72 dpi (screen use). Technique perspective control (PC). The ways to control perspective are twofold: by software/post-treatment, or by shifting the lens at the moment of making the picture (using PC-lens, or technical equipment/camera). Architecture: perspective is often confused with (lens)distortion. Making a picture of a building is most often done at a lower position, the building is seen as "flying away". Vertical lines are no more parallel, this reflects the reality. However looking at a building a human being knows the vertical lines are straight and parallel, and in most cases it is advisable to correct this. Painting/document: it is not always possible to photograph a document or painting correctly, having the camera in a perfect parallel position to the original. One can correct this at post-treatment using e.g. the function "distortion". 6

7 Technique stich. "Stiching" is combining several picture files, and is used very often for panoramic landscapes, interiors, but also for altering picture resolutions (e.g. reproduction of painting, tapestry, large size document). 7

8 Technique fine tuning. Digital picture file post-treatment is very important, it distinguishes the poor and good quality, from high quality and beauty. -levels: this is actually changing the space between dark and light, so called "dynamic range". Some scenes have a very large spectrum between dark and light parts, e.g. interiors (windows), landscape (bright sunlight). For items that don't have so much difference in dynamic range, it is often better to "cut off" yielding a more brilliant result. Sometimes it is necessary to make use of HDR to capture both very dark and light parts. -filters: there are two kinds of filter, a real one put on the lens, or "software". Using filters at post-treatment can be very useful to eliminate white spots, irritating elements, camera sensor noise or dust spots. -select: it can be very useful to use a selection, only a part of a photo, to make specific corrections -colour correction, density, brightness: the best way is to make good correction first on RAW file development. A good photographer rarely makes big corrections on brightness: one has to choose a good exposure while shooting the picture. 8

9 Organizing the picture files There are only a few commonly used picture file types used: - JPEG (or JPEG 2000): compressed and easy in use. However making image corrections is restricted. Best use is for final picture files. The image quality/compression level can then be selected. - Tiff (or PSD, PDD etc): this is a complete file, 7 to 10 times the size, advisable to store the files in maximum quality. - Other types are PDF, PSB (very large files) Metadata: these are all kinds of (written) information enclosed in the image file. This can be comment, copyright information, location, author, keywords, labels... 9

10 Analogue to digital: scanning the "old" pictures For conservation and diffusion of (old) photographs, film or photographic plates, one digitises them using a scanner, to convert analogue image to digital. There are different types of scanner depending on quality level, price setting, type of original: - Flatbed scanner. This is a kind of a dark box, where a kind of a (digital) camera together with light source is moving over a (glass) flat surface. An image of the (flat, two dimensional) original is projected on a sensor and captured in a digital file. Most flatbed scanner can reproduce up to A4 (21 x 29,7cm), some go up to A3 (29,7 x 42cm). - Vertical scanner. This is kind of a fixed setup of a camera, movable vertically above a platform whereupon the original is placed. There is only one make still on the market, Imacon, that is also suitable for film scanning. Others are specifically for use in museum and archives, and for reproducing large format documents (A2 up to A0). This offers the highest quality but are expensive equipment. Note: Drum scanner: Highest quality but disappearing, and only for film. Scanning resolution. As a rule of a thumb three resolution levels are in use: 300dpi (118px/cm) for high quality printing, 72 dpi (28px/cm) for screen and 2000 to 4000, depending on scanner possibility/quality level for film. Paul M.R. Maeyaert free lance Photographer, working on Cultural Heritage items since more than 40 years, cooperating with the LoCloud project, with the aim of including his collections of art photos into Europeana, La Rectoria de Sallent E Pinell de Solsona pmrmaeyaert@gmail.com Paul MR Maeyaert 10