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Message: <blockquote data-quote="Surveyor" data-source="post: 1265042" data-attributes="member: 50720">Hello Edz; I know that different procedures and different principles define what we expect to find in any testing protocol and we generally find what we expect to find. I am beginning to understand your expectations from your testing procedure but thought it may be interesting for me to apply my concepts to your data. Let me add that I find your data to be very consistent, we just have different expectations from it. As a reference point let me state that my visual acuity is far from the best in the world. From year to year, it bounces around from 20/20 to 20/25 in the right eye, left a little worse, with minor astigmatism in both. For the last couple of years the doctor has noted that I have light/mild cataracts forming, probably the source of most of my loss of acuity. Also during testing, I have found that the light levels play an important part in my acuity. I normally test resolution at 15 EV (82,000 lux) at 5200K (normal daylight level) and have noticed that when I am in a hurry and just want a rough estimate, I use normal room light at about 6 EV (160 lux) at 2800K and always resolve at least 1 element, usually 2 elements, worse on the USAF chart (12%-25%). From my testing experience, my acuity usually runs from 110” at the good end to the mid 140’s at the other end, so I use a value of 150” to be conservative. Based on the statements “In humans, the maximum acuity of a healthy, <a href="http://en.wikipedia.org/wiki/Refraction_error" target="_blank">emmetropic</a> eye (and even ametropic eyes with correctors) is approximately 20/16 to 20/12, so it is inaccurate to refer to 20/20 visual acuity as "perfect" vision.” and “The ability to resolve this therefore requires 1/5 of the letter's total arc, which in this case would be 1 minute. The significance of the 20/20 standard can best be thought of as the lower limit of normal or as a screening cutoff. When used as a screening test subjects that reach this level need no further investigation, even though the average visual acuity of healthy eyes is 20/16 to 20/12.” andHenry’s and your results I would expect 72” to 96” to be average, which is confirmed by your comment a few posts ago about 75” being found to be the average in recent studies (I will leave it up to Elkcub to decipher the statements in bold). So, when I look at your data, what I see is that the acuity level is about 75.6” at 7x and generally increases to 97.5 at 20x, which I would expect since I think to see proportionally smaller resolution differences would require proportionally more acuity or magnification, the rounding of the “knee” before the plateau in your resolution plot. The number of instruments and the values lead me to believe that the average would be 89.1” with a Std. Dev. of 7.3” (roughly +/- 10%) or approximately plus or minus one element on a USAF chart. Allowing for different magnification levels, cyclic changes in acuity and, probably, different light levels, I find the data amazingly consistent. While I know that your results are based on visual observations with no effort to reach the limiting resolution, I see a need for auxiliary “boosting” in the data. Based on the ISO minimum resolution limits for “General Purpose” instruments, all of these fail, except the 20x80 units with lower than 5” observations, using the following criteria:Limit of resolution a in object space (seconds of arc): with exit pupil diameter < 4.5 mm      res<= 300 / D with exit pupil diameter > 4.5 mm    res<= 60 / powerso it would be difficult to make a statement whether or not these met minimum standards with just this information.Thanks for your input and opinions, have a good day. Ron</blockquote>

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