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Adapting Video for VI Learners
Design issues and approaches
General principles related to VI needs
Below, we draw together the main hints and tips to keep in mind as you create your new educational video or multimedia pack. Our hints fall into two categories. The first has to to with primary design: things to do or avoid to make a given video clip easy to see. The second category of advice suggests what to do when there is no way that the video can be sufficiently enhanced: when you have to consider supplementary materials.
Educational video will not be novel for VI learners. Like their able counterparts, visually impaired people watch an average of 24 hours of TV per week.
However, the balance of design compromises differs between broadcast programmes and educational materials. Broadcasters use the medium to its contemporary artistic and technical limit to make their work attractive and attention-grabbing. This implies fast action, exotic shot angles, fancy titles and credits, multiple things going on at the same time. Many of these make modern programmes increasingly difficult for VI viewers.
Educational producers must also produce attractive materials, but they can take greater account of perceptual issues raised by mixed audiences. The result will be programmes designed more for understandability, legibility, and effective manipulation at viewing time.
People who are registered as visually impaired or blind have more residual abilities than you might expect: 7 out of 10 can use text if it is clear and large enough. Most visually impaired people lose their sight rather than being born with the condition: around 17 out of 20 have had progressive loss. This in turn means that most will have memories of better vision which will help them interpret audio and text descriptions from real experience. Even for congenitally blind people, visually rooted language including such things as colour descriptions comes to have associative meaning, with words like 'green' used with 'strawberries' being an alternative for 'unripe'.
Colour - (see also the References
section for links to in-depth coverage)
If your video is on cooking, don't rely on colour alone to help distinguish baking from eating apples...
Example: material with inherently poor contrast
Some material is difficult. In the clips below the intent is to show how cold misty air pushes in under warm clear air: the information is in the fog movement, which is in subtle shades. The second enhanced clip might be offered on a multimedia training pack to compensate.
A simple cursor, pointer, or bounding frame can help the VI viewer locate where critical action is taking place. The video shows such a cursor in operation to highlight a transient event.high quality enlargements
Although it is tempting to assume that pictures may be enlarged simply by using low vision aids or by taking advantage of computer operating system level enlargement tools, blowing up images in this fashion can lead to pixellation which renders the image unviewable. It is easy to build in high quality enlargements during development:
Example: Over-spread action
A clock is timing a physics experiment, with the action (a ball rolling down an inclined plane) being shown in one corner of the screen with the clock in another corner producing problems for those with restricted fields of view. The producer could have tracked the clock with the ball, or overlaid time readings at particular points on the way down the slope, or could simply have called out the times on the audio commentary.
(D)>Example: still frames
Here are two still frames, one from a digital camcorder with a high frames per second capture which makes it easy to see what is going on when the video is paused.
Example: Active and stylised textDesigning supplementary material:
Designing video programmes for mixed audiences can be difficult. If working to the guidelines above becomes too painful, consider designing-in supplementary material. Supplementation built into primary production is both easier and more effective than adding material later.
If your medium is linear (VHS
tape, DVD), then all the techniques we have described in the add-on section
still apply. You can plan for supplementation, bearing in mind what channels
will be available to you on the delivery medium you choose (with more
on MPEG-2 systems like DVD, for instance, than on VHS) -
However, as the primary designer you can go much further. You can consider providing special versions for VI viewers in ways which add-on modifiers would find difficult. Properly planned for, there is no great incremental cost to producing a second variant of the teaching material with extended audio descriptions, high-quality stills, data bursts and supplementary views of difficult material on multichannel streams
If you are designing non-linear
materials then your ability to support learners with special needs
is massively extended, and as with the linear materials, need not cost
much more to provide. Because you can incorporate extra materials without
resorting to tricks such as borrowing audio channels for subtitling, you
can develop a single package to serve all users. Planning involves -
Web Browsers allow the user some control over the choice of font size to be used when displaying text. The two pictures show the same text being displayed in the default font, and then in a font of a more appropriate size. In either case what makes this work is an acceptance on the part of the materials designer that they may not have complete control over text layout. Relinquishing artistic control in favour of user flexibility is hard for many graphical and multi-media designers.