Human Factors: Visual ‘fiddling’ test
Visual ‘fiddling’ test (1979)
The IZF Visuology Department focused on basic visual functions (including visual acuity, colour vision and depth perception), instrumental vision (including scopes, thermal imaging devices, and brightness enhancers) and visual ergonomics (including lighting and typography). The prism test was an example application of basic visual function research.

In inspection and fine assembly and drawing work, close-up detail perception plays an important role, as it does, for example, in engraving topographic maps. For this ‘trinket work’, the IZF developed the ‘trinket test’ that can be used to test close-up detail perception. Because the ability to
near without glasses decreases sharply with age – especially over 40 – it makes sense to regularly subject employees, especially the elderly or those with eye problems, who are tasked with milling work, to perform this test.
The test had been developed in the late 1970s and came on the market commercially in 1983.
The test pattern consists of ‘Landolt rings’ in six sizes. The orientation of the ‘Landolt rings’ can be: bite left, right, top or bottom. The six sizes of the bites are: 0.12; 0.10; 0.08; 0.06; 0.05; and 0.04 mm. This pattern was presented on a frosted glass surface through a simple box, internally back-lighted. On the reverse side of the test, an enlarged print of the pattern can be found. Behind each line, the bite-size of the test pattern in mm is printed. In front of each line, the inverse of the bite-size is indicated by the character P of ‘Priegelindex’ and s number. The scale runs from P:25 – excellent to P: 8 – poor. This indication was chosen to avoid confusion with the indication for visual acuity (V), which does not usually exceed the value V: 3.


What detail one should still be able to read depends on the task. P: 25 can still be read only by young healthy eyes and by older people with special spectacles. However, few tasks will require this high requirement. Although it is difficult to draw up an exact set of requirements, we would like to recommend the following
diagram. The test result is taken to be the smallest line that is still read completely correctly.
Test result | Conclusion |
---|---|
P:25 | Excellent eyes for long-term fiddling |
P:20 | Good eyes for long-term fiddling |
P:16 | Glasses check desirable for prolonged fiddling |
P:13 | Spectacle check required for prolonged fiddling |
P:10 | Without eyeglass control unsuitable for short-term fiddling tasks |
P:8 | Spectacle check required |
*It should be emphasised that P:16 can usually be achieved without any problems with reading glasses.
