Vol. 9, No. 1• January 2010Q. The article in The NDT Technician on "Understanding Near Vision Eye Tests" was welcome and informative. How about one in the near future on verifying adequate gray scale differentiation for interpreters of radiographic film? There doesn't seem to be a lot of information available about what can be used for this type of vision test. W.H., Attica, Indiana. A. The ability of a person to differentiate between shades of gray is a requirement unique to the radiographic testing (RT) process. The question of how to do so and when it is required has been asked of the ASNT SNT-TC-1A Interpretation Panel in the past. The usual response is that how this test is performed is the responsibility of the employer. There is clarification on when the shades of gray examination is required in Interpreting SNT-TC-1A, Inquiries 08-2 and 08-3.* Inquiry 08-2 asks if a person seeking RT certification needs this test and the answer was Yes. However, 08-3 asks if a person being certified in MT, where gray particles will be used, needs the shades of gray test and the answer was No, and refers the reader to the response in 08-2 in which the Panel states, "Whether to test for color differentiation or gray shade differentiation is determined by which is appropriate for the method the individual is being certified in." I have been looking for specific eye examination methods that address shades of gray, but those I have found deal with larger objects in different shades of gray on a white background, not smaller objects and shade differentiations between varying shades of gray which are needed for the RT process. Since film readers must not only discern changes in shade but also a degree of sensitivity, it may be necessary to develop a shades of gray test specific to the RT process that will check contrast as well as sensitivity. I have some thoughts on this but will have to develop them more fully before bringing them out for consideration.
Respectfully,
James W. Houf
Senior Manager, ASNT Technical Services Department* Interpreting SNT-TC-1A can be found in PDF format in the Members Only section at www.asnt.org. A printed version can be purchased online at ShopASNT or by contacting the ASNT Book Department at (800) 222-2768. Reference item number 2040.
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