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Using Music Concepts to Understand    

Image Contrast          

By Glenda V. Such, M. Ed.


When addressing the contrast features of a visual image, it may be difficult to understand its variables.   This element of a visual image is important to discuss in lay terms, as it may be the single most important characteristic of images for people with low vision or visual impairments.  This short document will utilize the concepts found in music as an analogy to the factors decreasing or increasing contrast levels of images.

 To begin the process, imagine the world’s largest orchestra.   This orchestra has the instruments to play classical music heavy metal, punk rock, jazz, and easy listening.

 Within the orchestra there are an enormous number of different types of instruments having no sounds in common sound characteristics.   Examples of a few of these groups are the drums, the strings, the piano, and the castanets.   These groups when compared to each other are analogous to an image in high visual contrast to its background.  Made simple, if the drum is hit while a note comes from a violin, there is no mistake that two different items are present.

 Using this way of understanding image contrast, imagine the playing of two instruments at the same time that are extremely similar in the sound they produce.    For example, if a trumpet played a single note that was played at the same time by a long trombone, logistically and undeniably a difference would be present.  Each person’s ability and effort to determine that two different instruments were played would depend on many factors but most of all, their hearing ability to discern slight tone differences.

 Again, this is similar to contrast in images, if an image is much like its background, it is more difficult to discern and while many factors are involved, visual abilities are most applicable.

 With that now covered, what could be examples of high contrast and very low contrast.    The easiest to understand is black on white, or white on black.   This means absolute white on absolute black not off white with charcoal black.   Using those combinations are similar to using instruments that are not as distinctively different but are mealy in the same category as the original comparison.

 How much does that influence contrast?   More then expected.  An example of this could be the fact that bright yellow images on dark blue backgrounds are seen as good contrast.   While pale yellow on a sky blue background is very low contrast.    Musically, this is similar to playing a note on a tuba and a note on a banjo, then changing it to playing a note on a clarinet and a note on a base guitar.

 But is this the only way contrast is varied?   Again in comparing music to visual images, is the ability to identify multiple instruments playing at one time only influenced by their major instrument grouping?   Is the identification of the types of instruments and their numbers potentially effected by how loud they are played, how long they are played, and if other annoying sounds are in the   general listening area?   Yes to all these factors, and many more.

 Within the actual image’s contrasting characteristics are the individual’s own variables.   Much like in music, an event that reduces the individual’s average daily ability such as clogged ears from a cold, distracting actions by an outside repetitive or annoying sound, or even the interest in making an effort to discern the differences could effect just how much contrast is needed for easiest and accurate detection.

 Along that same line are factors in seeing a visual image that are effected by their physical location, the time period they need to be seen, and how quickly they need to be identified.

 One such example of these factors are extreme glare.   While glare in itself will be explained in full in a future article, its most basic impact on visual images even when provided in highest contrast must be mentioned.  Glare dangerously simplified is light that when viewed is harsh to vision and may produce even pain for some people.   The amount of glare needed to be present for it to be physically experienced as mildly annoying or debilitating to bring one to their knees is greatly effected by the part of the eye that is effected.  Some parts when damaged, clouded, or missing make the same amount of light viewed seem amplified, and when this light is seen as glare, any image is washed out or lost in the distraction. 

 To understand this in music terms, if light was any form of sound by any musical instrument, glare could be that instrument playing a note too high and harsh for comfort and hooked up to an amplifier.  Some could tolerate the sound, but if the amplifier was too loud, that same note would be painful.  

 In that same process, what if two separate musical tones were played that were in high contrast such as a flute and a guitar while at the same time a cowbell clanged and clanged away.  Then put the cow bell next to a microphone and how well does the contrast of the original two instruments, the flute and the guitar, hold up for easy listening?

 So to is the effect of glare.  If an image that is in high contrast is in a location where glare will effect the eye, so is the seeing of the image.  Examples of glare that are most obvious are bright sunlight, neon light, huge windows, computer screens, clouded windshields, sidewalk pavement, and snow.

 The more an image makes someone look into that glare, the less they are able to see the image and the less they are willing to subject themselves to discomfort.   This would be the same for someone who was trying to hear a piece of music.  If there is too much clatter to hear through, the music is lost.

 To avoid this and have the contrast of an image be seen and appreciated, check for its contrast first, then check that the glare does not work against the image.  An image physically positioned where a person must look into the sun to see it, faces the possibility that it will not be seen at all.  If the neon light has a person’s eyes closing to block the harsh glare, the image is gone. 

 Resolving these issues is not difficult, look at what is being created and then look at what surrounds it.  Music played in a subway station can be heard very well until a train arrives.  Then the music is gone, the musician keeps playing but the music stops.   So too can a bright green traffic light show bright at night, then with sunlight directly behind it during the day can t magically disappear.

 By Glenda V. Such, M.Ed.