17 minute read
COLOUR VISION
Defective Colour Vision in Orienteers
is it an issue?
Barbara Junghans, Garingal Orienteers
DESIGNING any colour coding system, say for Orienteering maps, requires an understanding of how humans see colour. It is well known that some people are colour ‘blind’, or really, colour vision ‘impaired’. Total colour blindness is extremely rare (everything seen only in various shades of grey). Typically, colour vision impairment is only partial and there is a vast range in the severity, with by far the majority having only a mild problem. For years, some event organisers have been aware of a handful of orienteers competing at top masters levels who have now been classified by the author as severely colour vision impaired. To discover the challenges they face with the current internationally accepted colour coding scheme, read on.
What part of the eyeball ‘sees’ colour?
The retina, the light-sensitive layer coating the inside of the back of the eye, has two key types of cells or photoreceptors that respond to light stimulation: the rods and cones. It is only the cones that are responsive to coloured light, and there are three subclasses of cones scattered across the back of the retina. One subclass is only receptive to light of red wavelengths, another to blue, and the remaining class is only responsive to green. It is amazing that by simply varying the intensity or the ratio of the red to green to blue light ultimately results in the rainbow of perceptions enjoy by most of us. As there are three subclasses of cone cells, it can be appreciated that there might be three ways in which colour vision can go awry. If one class of cone photoreceptors is faulty, the blend of information summated from neighbouring cones to be passed up the nerve pathway to the brain will be distorted, and the colour seen will not be the same as the colour of the original object.
What types of colour defects exist?
Hence, if we also count the normal situation, there are 4 different categories of colour vision: 1. Normal: (all red wave length-receptive, green wave lengthreceptive and blue wave length-receptive photoreceptors function normally). 2. Protan: a red/green defect (the red-receptive photoreceptors are faulty or unreceptive) that is uncommon (~1-2% of men, rare in women). The defect is typically congenital and without any other associated ocular consequences, but may be acquired from ocular or other nerve diseases. 3. Deutan: a red/green defect (the green-receptive photoreceptors are faulty or unreceptive) that is relatively common (~6% of men, 0.5% women). The defect is typically congenital and without any other associated ocular consequences, but may be acquired from ocular or other nerve diseases. 4. Tritan: a yellow/blue defect (the blue-receptive photoreceptors are faulty or inactive) that is very rare except in some eye diseases. This condition is more common in ocular diseases affecting predominantly the elderly, e.g cataract or age-related macular degeneration. However, visual acuity, and hence the ability to see fine detail is typically also severely affected, probably limiting reading Orienteering maps. The 3 classes of persons who have abnormal colour vision (loosely known as protans, deutans and tritans) exhibit a wide range of severity from very mild (referred to as having protanomaly, dueteranomaly, tritanomaly, or being protanomalous, deuteranomalous, tritanomalous respectively) to severe (referred to as having protanopia, deuteranopia, tritanopia or being a protanope, deuteranope or tritanope respectively). Persons with ‘anomalous’ colour vision only confuse colours in the lighter pastel shades, and are actually able to reliably identify the more saturated or intense versions of the colours for which they confuse the paler correlates. On the other hand, persons with the ‘opia’ defect have problems even when colours are relatively saturated. Hence, any two persons with a colour vision defect, even within the one class, will likely have differing difficulties interpreting colour coding.
How do persons with defective colour vision see the world?
Figure 1 shows firstly how a person with normal vision sees the entire range of colours, and then, how the three classes of colour impaired people might see those same colours. This is possible by submitting the rainbow image to the online service www. vischeck.com. Vischeck will convert any image you upload so you can see how your image is believed to appear to persons with any one of the three classes of colour vision defect. Or, you can download a plug-in ‘filter’ if you have Adobe Photoshop installed on your computer and then apply this filter yourself to any image
you open in Photoshop. The remaining palettes in Figure 1 were generated in this manner.
An alternate way of understanding the problems that might beset persons with colour defective vision is to study the radiating lines that have been superimposed on the protan, deutan and tritan palettes above – these are known as ‘confusion lines’. Any colours along the one line will all look the same to the colour defective person, only the intensity varies. If you mentally overlay the protan’s radiating lines back onto the original rainbow coloured palette to the left, you can visualize those colours seen by colour-normals that will be indistinguishable or confused by a protan. Similarly, you can mentally overlay the lines off the deutan or off the tritan palette. Notice that the upper confusion lines of the protan and deutan profiles are similar to each other, both confusing red, yellow and green. However, the lower confusion lines indicate that the protan also confuses red, purple and blue whereas the deutan confuses only purple with blue. On the other hand, the tritan person confuses yellow-based colours with blue-based colours. This places the tritan’s situation diametrically apposed to both the red-green colour defective classes. So the challenge in designing a colour code is to never use colours lying along any one confusion line for any of the three classes of defective colour vision! Only then can one be sure that the chosen colours are distinguishable by all.
Figure 3. A portion of the Brookstead map used for Day 3 of the 2009 Easter 3-Day in Tasmania. On the left is how a person with normal colour vision sees this map. In order, progressing rightwards, are simulations of how protanopes and deuteranopes are believed to see the same section of the map respectively (according to Vischeck software). Figure 4. A portion of the Lincoln University sprint event map in South Island, New Zealand, used for the 2009 Oceania Championships. On the left is how a person with normal colour vision sees this map. In order, progressing rightwards, are simulations of how protanopes and deuteranopes are believed to see the same section of the map respectively according to the conversion using Vischeck software. Figure 2. The Australian version of the International Orienteering Federation’s PMS colour swatch for drawing Foot Orienteering maps. Top left is how a person with normal colour vision sees this map. In order, progressing top right, bottom left and bottom right are simulations of how protanopes, deuteranopes and tritanopes are believed to see the same section of the map respectively (according to Vischeck software). How do orienteering maps look to the colour defective orienteer?
Can colour vision impairment affect the sport of orienteering? Through the use of Vischeck software simulations, Figures 2, 3 and 4 respectively reveal how the International Orienteering Federation’s colour swatch, as well as sections of maps used for Bush Orienteering and Sprint Orienteering are likely to appear to orienteers with severe colour vision defects. Basically, for protans and deutans yellows and greens appear somewhat similar, separated only by shades of intensity. It can be seen that orienteering ‘yellow – open’ and ‘green – slow run’ are seen as yellow/yellowish-brown or yellow/ ochre by the red/green colour defective orienteer. The map sections chosen highlight one dilemma in searching for an alternate strategy to using colour as the predominant approach to convey spatial information: that even for ‘colour normals’ the smaller the patch of colour on the page, the harder it is to recognise which colour has been employed.
Further considerations
What factors contribute to the ultimate appearance of a coloured map? For any object, how the eye functions and the intrinsic colour of that object are obviously important to how it will appear. For a map, the ‘object’ is the coloured ink on the paper. However, how the map creator intended the colours be seen may not come to fruition because dyes age and deposit differently on various papers. Although the different colours are achieved by defining simple ratios of red ink to blue ink to green ink, the final outcome will depend on the ageing of the pigments, the type of paper (highly absorbing, poorly absorbing, plasticised), the type of printer (can it be set to handle different types of paper), the speed of the paper feed through the printer (affected by the degree of wear and tear), etc. Then, once the pigment is on the paper, the lighting under which it is viewed is also important because it is the reflected light off the pigment that determines what the eye receives To evaluate colours on orienteering maps appropriately, dry maps must be viewed under light as close as possible in character to sunlight (technically, using Illuminant C). One should not compare the map off the home printer against the IOF swatch whilst standing under a bluish fluorescent light or a rich warm light. To understand the minefield regarding truth in colour representation, simply compare a picture on a computer monitor with the version printed out on paper. The phosphors of your LCD have intrinsic settings that can be changed to render colours with a particular bias, and as explained above, the printed version will also have intrinsic bias. Indeed, the figures used here for this article were created on a computer, printed out as a swatch or map, scanned on a Canon CanoScan Lido 20 scanner, and re-printed according to The Australian Orienteer printer’s colour gamut specifications. It has been shown that the Australian version of the IOF colour swatch and a few maps printed ready for use, contain colours that lie along one or another confusion line for persons with any class of colour vision defect1 .
Suggestions
Clearly, the figures show that orienteers who are colour vision impaired would have more difficulty trying to decipher their map. Indeed, it has been shown that colour affected individuals take longer to analyse graphs and maps. This is even so if the maps are made using ‘colour-impaired friendly colours’ and the affected individuals are told this (out of habit?). Figures 1 and 2 dramatically show the restrictions on any potential colour codes if orienteers with severe colour defects are to be accommodated. It is unrealistic to expect a colour coding scheme for Orienteering maps that will be recognisable by all three classes of persons with colour vision defects. Hence, as tritans are extremely rare, or have eye disease that would of itself reduce vision (probably to the point that fine detail on maps would be unreadable), it has been suggested that only confusions for protanomals and deuteranomals be addressed. If only relatively saturated colours were used on maps, the large majority who have only mild colour impairment would be far less affected. The existing colours in the IOF swatch could have their shades tweaked so that none lie along any confusion line. For example, if the green used to indicate bush density were made to have a little more blue in it, the new slightly aqua-looking green would be more readily discernible against the yellow that indicates open land by both protans and deutans. However, colour is not the only form of coding, and alternatives such a geometric coding can make colouring somewhat redundant; e.g. others have suggested that a brown cross and a green cross could be further differentiated as four star/six star symbols, and of different sizes. Cross-hatching or patterning is also commonly used on graphs and some maps. However, because very small patches of colour are commonly required on orienteering maps, it must be remembered that a geometric pattern may become uninterpretable when the dimensions are very small. Use of fine black outlines for one colour might also be feasible. To counter the fact that ageing of dyes or variations due to the printing process may have affected the ultimate colour outcome on the particular paper type chosen for an event, a legend that has been printed at the same time as the map itself should always be available for colour-impaired orienteers (either by way of being on the map itself, or as a separate item available at the registration desk). In this way, colour affected orienteers can at least read the map’s presentation of the subtly different shades of yellow/ochre, etc, against the mapped features for the terrain in whichever way they personally read the map. Map-reading performance can also be assisted by using particular coloured lenses (simple squares of flat acetate film, say hung round the neck for occasional use like a lorgnette). These long wavelength pass lenses alter the relative brightness of specific colours and thus enhance differences between colours that would otherwise appear identical or almost so. These lenses have been marketed under names such as X-Chrom, Chromagen, Colormax, Coloryte and Colorview. However, such lenses will distort other colours and superimpose a blue-yellow deficiency over the existing red-green deficiency, as well as reduce visibility in dim light. Certainly, these lenses do not restore colours to normal appearance for the colour vision impaired person. Therefore, their use in Orienteering might be limited to situations when doubt exists for the meaning of a colour on the map. Feedback from one recreational orienteer was that the lens was immensely helpful. However, other orienteers have found them not so helpful. Again, the diverse impact of colour defectiveness becomes apparent. These lenses are generally only available through the Colour Vision Clinics at the Schools of Optometry at UNSW, University of Melbourne or Queensland University of Technology – although a few optometrists in private practice who have a particular interest in colour vision might have access to some of these lenses. In summary, because it is known that some persons with the severest forms of colour vision impairment want to enjoy the sport of Orienteering, and presumably many more somewhataffected individuals are participating, the IOF colour specifications need an overhaul. The IOF is cognizant of the scientific evidence indicating the lack of fairness in the current colour coding system used for orienteering maps and has this year instigated a review of the colour specifications. In due course you might notice a slight change in the colours on your maps – and now you know why
1Footnote: the publication “Orienteers with poor colour vision require more than cunning running” by Jennifer Long and Barbara Junghans, Clin Exp Optom 2008; 91: 6: 515–523, has more details regarding this matter and contains a review of the literature pertaining to the points made above. If you would like a copy of this article, or wish to have further information on where you can have your own colour vision status assessed, email Barbara Junghans at School of Optometry and Vision Science, UNSW, b.junghans@unsw.edu.au
Barossa and Adelaide Hills
SOUTH AUSTRALIA has arranged for all events of the Carnival to be within 100km of the Adelaide metropolitan area and either in, or in close proximity to, the Barossa Valley. The Australian Long Distance Championships will be about 5km from Tanunda, the heart of the world renowned Barossa wine region. The event areas have been chosen near Adelaide, so competitors and families can enjoy the tourist delights of Adelaide, the Adelaide Hills and the Barossa Valley, without great distances to travel .The event areas are also within easy reach of Adelaide airport and near the main highways to the Eastern States. The Middle Distance Championships will be held adjacent to the Humbug Scrub Sanctuary which was established in1905. The event will be largely on an area where mining was carried out in the 1800s, with interesting contours from the mining. Many ruins of old buildings from the abandoned town can be seen on the map. The mines were called Lady Alice and Lady Edith which we believe were the names of the wives of the mine managers, hence the name of the map. This area has never been used for Orienteering before. The Long Distance Championships at Tanunda are on a new map. This includes part of an area, mapped by the late Irena Palmer in 1993, which has not been used for a number of years. The terrain is spur/gully with extensive areas of rock and good runnability that should be enjoyable, although testing, for all age groups. An old gravel mining quarry will add variation to the courses. The Sprint Championships will be held at Trinity College on the outskirts of Gawler, west of the Barossa Valley. And the Relay Championships will be on intricate spur/gully terrain near Walkers Flat, east of the Barossa. The area has not been used for a number of years and is currently being remapped. It is known for its fossilized oyster shells from a bygone era. Williamstown will be the centre for the Schools camp. Individual and Relay Championships for Schools will be in nearby areas. Public events will be held in conjunction with these events, with a barbecue and night event following the Schools Relay. Information will be forwarded to the State school coordinators in due course. Peter Cutten - Carnival Coordinator: (08)3321580
Advertise your event in this space
You can have a 5 x 8 cm event ad for just $50 In colour, if we have room, otherwise black & white
Just Don’t Mention
Orienteering
THE SILVA DuO Adventure Race Series is an innovative new concept designed to attract new members to our sport by getting them to take part in an Orienteering race without even knowing it! In recent years there has been a boom in adventure races run by professional organisations and most often going by the names of their major sponsors – Kathmandu, Teva, Anaconda, Mountain Designs. Many of these races are Orienteering, pure and simple, involving foot and mountain bike legs with navigation. They even use our very own Orienteering maps (for a nominal charge!). So, if these races are just Orienteering under another name why is it that they get 200 or so 20 to 40-year-olds clambering to enter online, paying $100 each to enter? Is it the quality of the courses? No, as the maps are, at best, poor reproductions of Orienteering maps and the controls are often misplaced because the guy placing them is probably the race organiser with a degree in event management but no experience in course setting. Is it the slick promotion? Probably: Ads in national magazines and cool looking websites have a huge influence over today’s techsavvy, advertising-aware generation. Is it the big name sponsors? Probably: they provide the good prizes and add a certain degree of professionalism and kudos to the event’s image/ brand. Is it because it is called an Adventure Race and not Orienteering? Most certainly yes! Like it or not there is a stigma attached to Orienteering that puts off the very people who seem to want to have a go at Adventure Racing, vis-a-vis the market we want to tap in to. With the answer to this last question in mind a group of orienteers in Victoria has developed the SILVA DuO adventure race series. The first series got under way earlier this year and preparations for the next series of 3 races in early 2010 are well under way. The races will include foot and mountain bike legs with easy navigation, they are close to Melbourne and the wining time is around 90 minutes. The SILVA DuO model is different to how other Orienteering events are run though: there are just 2 courses (long and short), we’re offering great prizes and entry is on-line by credit card. Our promotion is extensive: we’ve got the big name sponsors on board, a great website, flyers distributed at other adventure races and half page adverts in national magazines like Outer Edge, Outdoor and Australian Mountain Bike which have a combined distribution of hundreds of thousands. Our goal is not to make profit - read all other Adventure Races which need to pay their full time organisers - it is to attract new members to our sport. What better way to promote Orienteering than to run an event where people come and try it without even knowing! If, like me, you’re concerned about the future of our sport then start spreading the word about the SILVA DuO series and let’s see if we can’t tap into a new market of potential members. Dion Keech – SILVA DuO Adventure race series director
