Plant Identification

by Anna Lawrence

  Botanical painting

  We include some details on the Virtual Field Herbarium website (http://herbaria.plants.ox.ac.uk/VFH) to help general watercolour artists produce botanical paintings. Paintings are less commonly encountered in modern field guides

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  than drawings as they are the most expensive format to create, and are no more accurate to use or cheaper to print than colour photographs. They do, however, have some potential to combine the advantages of photographs and drawings. The results at their best are aesthetically pleasing, selling a field guide on their own merit, and doubling as publicity material or the originals as gifts for sponsors. A good painting can capture the

  ‘soul’ of the plant; a good photograph, unless you are a very lucky or inspired and patient photographer, can usually only manage to capture its body. When the Ministry of Lands in Grenada chose a design for T-shirts for publicizing World Food Day from our collection of 300 images of Grenadian plants, they chose paintings, rather than photographs or drawings. Furthermore, we are perhaps saturated with photo and video imagery, and paintings of plants make the statement: ‘we are attaching importance to this species: it is special’.

  To create paintings, you need the services of a good botanical artist, otherwise you should forget the idea; so check the price before thinking further. Fine details – for example, in inset boxes – are not as commonly included in paintings if they are to double as aesthetic objects; but a good design can incorporate all the necessary detail. Many beautiful, highly practical and popular field guides have been illustrated mainly with paintings (for example, Blamey and Grey-Wilson, 1989; Wise, 1998). These might, on the whole, come under the heading of labour of love, rather than a practical model for aspiring field guide creators in the tropics; but they do show the massive potential of painted field guides.

  Even when your local artist is too expensive or busy for you to consider for the job of illustrating your entire field guide, it is well worth thinking of commissioning a few inspirational plates – for example, for the front cover, publicity posters or occasional insets – as it may well increase sales or stir a deep interest in your publication and in any plants you want to publicize.

  Field tests of painted images in Grenada

  Amateurs in our trials in Grenada (see Case study 8.1) marginally preferred photographs to paintings as they were perceived as more realistic. They were of about the same accuracy as photographs in name-that-plant trials, and slightly more accurate than drawings. The medium is not ideal for difficult colour subjects such as bark slashes and tree trunks, even if you can persuade your artist to work inside the shade and discomfort of the rainforest and in an environment that is not ideal for watercolours.

  USE OF COMPUTERS FOR HANDLING ILLUSTRATIONS

  In some cases, illustrations for field guides of any format may be destined for use on a computer as well as, or even instead of, on paper. In other cases, a printed field guide may be illustrated with images from a digital camera or scanner. In both of these cases, use of a computer for manipulating your illustrations is inevitable. However, even where computer use is not essential, field guide creators who have access to a computer have much to gain by digitizing illustrations and managing them on a computer. Software for facilitating various aspects of imagery on a computer is discussed in Box 8.8.

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  BOX 8.8 LAYOUT AND OTHER SOFTWARE TOOLS

  When preparing simple illustrated documents of a few pages, normal word processors such as Microsoft Word provide tools for the layouts of images and text. For more professional layouts, particularly where all or many pages follow a predefined template, a desktop publishing programme, such as Adobe Indesign or Quark, is more appropriate.

  We laid out the pages for all our test guidelets for the Forestry Research Programme (FRP) trials using Microsoft Word. This allowed good colour printing of subtle bark shades, large file sizes, reasonably accurate alignment, and so on. Tables, into the cells of which you drop photographs or text, are useful alignment tools. If all pages are to have the same layout, make a document template – for example, containing tables, text boxes and dummy text in various defined styles to ensure consistency. Although top copies were created on an ordinary Epson inkjet printer directly, to produce six laminated copies of the 120-page colour guide, we decided to use a printing agency. For this purpose, and because we wanted the printer to produce all guidelets in various sizes for single files, we created Adobe Acrobat files of the guidelets (see Box 8.9).

  Digital image databases

  There are a number of software packages that facilitate the handling of images on computers. Two leading contenders are Thumbs Plus (www.cerious.com), which is currently slightly more advanced and slightly more expensive (at US$60), and ACDsee (www.acdsystems.com ), which is slightly cheaper and had fewer database functions.

  However, this software is evolving very quickly, so by the time you read this there will probably be other contenders. We have used Thumbs Plus extensively on the FRP guides project (see Case study 8.1) and consider it very easy to learn and hard to find fault with.

  Key points to look out for in such image-handling software are:

  •

  ability to automatically analyse and show thumbnails for all files on your computer and on removable disks;

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  ability to perform basic image handling (for example, contrast enhancement, cropping and rotation) from within the software;

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  batch renaming, editing (for example, file size reduction) and conversion of formats;

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  database functions, such as user-defined fields (like linked specimen numbers) – it is useful if the database file can be accessed by external database software;

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  gallery functions, where the same picture can appear in multiple virtual folders without the image file being duplicated (for instance, if you have your images arranged by plant family, you could have one gallery for bark types, one for rare plants, one for medicinal plants, and an image occurring only once on your disk would appear to be present in four separate folders);

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  when printing slide sheets, or multiple images per page of your image collection, make sure the software does not simply print the thumbnail, but recomposes each image from the original in order to make the best quality possible of the allocated space on the printout;

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  ability to make distributable CD-ROMs or web pages directly from selected folders or galleries;

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  linked view mode, where you can open two similar files, and when you zoom into or pan across one, the equivalent portion of the other files are shown side by side;

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  annotations and user fields for image descriptions should be printable adjacent to the images.

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  It is important to understand and use appropriate file formats for your digital imagery – without care you might lose important information or use up unnecessary disk space (see Box 8.9).

  Advantages of handling your illustrations on computer

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  It is easy to lay out, scale and modify text and drawings on a computer.

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  It is therefore easy to ‘repurpose’ your information – for instance, to make a poster or computer key with the same images as used in a printed guide, or to publish your images to a web page.

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  Digital imagery can be backed up and archived.

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  Digital imagery can be exchanged through email, and this circulation can be useful for verifying the utility, accuracy and name of the plant in question.

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  For limited print runs of guide material of limited circulation, it may be economical to print all of your field guides directly from the computer, and do without a printing agency altogether.

  Disadvantages

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&nb
sp; Computers with a high enough specification may not be available, even if adequate for handling the text of a field guide.

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  It costs time and money to digitize images from drawings and paintings.

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  New skills may have to be learned to operate the software.

  BOX 8.9 GRAPHICS FILE FORMATS

  When you save a file on a computer from most image-editing software, you have an option to choose one of the many, often more than 20, file formats supported by that software. A file format is like a language for storing and communicating information. Image formats are very far from being equivalent; so an important early decision when developing a set of images for your field guide project is what format or formats to use. Most programmes, for instance Adobe Photoshop, Corel Draw and Paint Shop Pro, have their own native format.

  If you are creating an image, you may as well use their own format while working on the image; but these are not the best formats to use when you want your image to be employed more widely – for instance, in your field guide document or web page – even if some of these proprietary formats are widely ‘understood’ by other graphics applications.

  Translation from one format to another is usually as simple as opening the file and saving it in a different format; but there is a high chance that some of the information content will be lost in the process.

  The internet has many pages devoted to discussing the various strengths and weaknesses of the different formats. We can simplify the various pros and cons to a choice between the following.

  Vector (and metafile) formats for maps and diagrams There is, in principle, a distinction to be made between vector type images, which store image information as abstract shapes, fill patterns and so on, and raster imagery, with information on the pixels, or points, of which pictures are made, much like the dots on a traditional film or printed article. This distinction is blurred by certain formats being able to

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  represent images in both formats – for instance, EPS (postscript format) and Windows metafile (WMF) or enhanced metafile (EMF), and the newest SVG (scalable vector graphics) format designed for use on web pages. Maps and CAD (computer assisted design) images (for example, architect plans or technical drawings of engines, or in principal floral diagrams) are generally best produced as vector images. Anywhere that the illustrator is likely to want to adjust and edit the path of lines, the shape of outlines or the relative position of objects rather than the subtle shifts of colour or fill density is best represented in a vector format – only in this format is the line itself retained in the file format. One of the main assets of vector imagery is that you can reproduce these images at different sizes, and straight lines never display jagged edges as you ‘zoom in’.

  Maps themselves represent a special, largely vector-based, type of image often useful in field guides. Map-making for field guides is a specialized pursuit that we cannot cover in any detail here; but many levels of geographical information system (GIS) software such as Arc View, MapInfo, Atlas GIS, IDRISI and so on are available for this purpose. GIS applications usually support their own specialized suites of various file formats. If you convert an Arc View or MapInfo map to DXF (drawing exchange file) format, or export to a bitmapped format like JPEG (Joint Photographic Experts Group), you may retain an image resembling your map, but you are likely to lose much of the underlying and linked geographic data.

  Bitmap images

  This is the ubiquitous format used by most modern computers for displaying images on your screen. The display area is broken up into a metric of dots of pixels, whose colour is defined. The number of colour types possible for each pixel (colour depth) and the number of pixels in the picture determine the quality of the image. There is little problem converting vector files into a bitmapped format; but the converse is not so easily achieved.

  Resolution

  Printers will generally work with up to 2400 dots per inch; but 300 dots per inch will still produce realistic images. When considering what resolution you need for your imagery, consider the maximum possible physical size you may need the image to appear at in your publication. If the guide is intended to be a document, then you can establish the minimum number of pixels required by multiplying the final printed size (say, 2 inches) by 600 dots per inch (speak to your publisher or printing shop early on in the project). This would suggest an image size of 1200 x 1200 pixels; so whether you are scanning a picture or choosing a setting on your digital camera, this picture resolution is what you should have in mind.

  There are other factors, though, and a picture with 300 dots across it can be perfectly usable in a field guide. Many say that for colour images you only need to assume a 300

  dots per inch resolution when scanning – and that any more is superfluous, more dependent upon the colour quality of the image and the printing device. However, for line drawings, where sharpness is vital and images might be examined very closely, we would recommend a higher resolution. The authors prefer to work on the safe side and scan all original artwork at 1200 dots per inch. This has the advantage of always providing a safe margin in case of changed decisions or better printers:

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  Remember that it is easy to reduce the resolution of your image later, but impossible to increase it usefully. Taking pictures or scanning images is always time consuming, and one should not need to repeat it later.

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  Table 8.2 File space required (kilobytes) for different formats and types of image Image type:

  Line drawing

  Line drawing

  Painting

  Photograph

  Number of

  pixels

  1802 x 1928

  1000 x 1000

  1000 x 1000

  1000 x 1000

  BMP or

  TIF without

  compression

  3300

  978

  2900

  2900

  TIF (with LZW

  compression)

  93

  109

  1100

  1800

  PNG

  99

  87

  853

  1500

  JPEG 95%

  353

  189

  172

  467

  JPEG 75%

  353

  115

  120

  167

  JPEG 50%

  288

  86

  77

  97

  Note: JPEG percentage figures are for quality (high quality, no compression =100%) Source: William Hawthorne

  a

  b

  Source: William Hawthorne

  Figure 8.6 The problem with saving the same compressed JPEG file too often: (a) detail from original scan; (b) detail from 50% JPEG quality (saved five times)

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  •

  There is no point scanning above the optical resolution of your scanner. You can inter-polate extra points later using basic image-editing software.

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  Scan line drawings at a standard resolution, at least 600 dots per inch (dpi), preferably 1200 dpi, even if they have already been drawn larger than the size required. By scanning all images at the same resolution, it will be easier later to arrange for all images on the same page to be at the same scale.

  Colour depth

  24 bit or 48 bit colour images are needed for colour photographs. 8 bit colour images are useful only for diagrams. A line drawing is best scanned with 1 dot per pixel and high resolution, although in some cases they have to be converted to grey-scale images (with 8

  bits to represent shades of grey for each pixel) before they can be edited.

  Table 8.2 shows the savings of file space (and therefore faster transmission across the internet) possible for colour pictures with increasing JPEG compression (the bottom three rows) – the more colours and the blurrier the
original, the better the compression. Figure 8.6 shows the minor artefacts that arise in a JPEG picture, After opening and saving the same file five times in a row with the JPEG quality set to 50%. Although relatively minor, they can become worse with every resave. Better-quality settings lead to similar, but smaller, blemishes. The problems are not likely to be noticed even on printed field guides.

  Which image format is best for use with botanical field guides?

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  Use tagged image file (TIF) format, with the compression options set to ‘on’ (for example, LZW) for line drawings.

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  If you want to use a standard format for all your images, line drawings and colour, a good all-rounder is the newer Portable Network Graphics (PNG) format (with appropriate settings – for example, full 24 or 48 bit colour.

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  Where space or transmission speed on your computer is an issue, use Joint Photographic Expert Group (JPEG) file interchange format with around 75–95 per cent (fairly high) quality setting. This will reduce time for downloading files and storage space by a factor of six to ten times over the next best option for compression, which is PNG format.

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  Digital cameras often produce images with JPEG format anyway, so there is nothing to be gained by then converting them to PNG format (since the minor damage is already done) unless you intend to repeatedly edit your photographs.

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  Keep an archive copy of all digital photographs before they are edited.

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  If you ever need to edit and repeatedly save a JPEG file, convert it to TIF or PNG