Solar eclipse glasses shade 14 welding glass lenses

12 seemed ok if i held just welding glass in my hands an inch or so from my nose. I found this to be a little too bright in a welding helmet where there is not much ambient light. 12 was the darkest glass they had.ДЄfter staring at the sun for a while with various combinations, Here are my observations.

I bought the last of the welding glass off the shelf at the local shop today. The formula above are given in T and that is how the calculations were conducted. However, OSHA has lower safety standards for welders as they would permit SN11 minimally when ANSI and AWS say SN14. I would not use any combination of lenses that did not exceed the single SN of 14. Yeah! This works out to an SN15 (not 16), so better than SN14.ДЄs far as safety goes, - better safe than sorry. A combined SN11 + SN5 give you a combined transmittance of 0.00000099. But the higher the numbers, the better the results. If you run the math here, two lenses with an SN of 2 will give you the transmittance of an SN of 3. But algebraic law of logarithms allow you to add the log of two numbers. Transmittance is a log function (non-linear) and therefore simple addition does not work with SN of multiple Welding lenses. Would we expect addition of lenses to be linear? Such as 2+2=4? No. According to the website, the UV and IR requirements are less stringent than the visible range and the calculations are more complex. Damage can occur in the UV and IR regions that could effect tactical vision or night vision within the periphery of the human range. This equation is for the visible light range only as discussed on the link above. Please note the number of decimal places is off by an order of magnitude. A Shade Number 14 by the same equation has a T of 0.0000027. So rearranging again /7 = OD OD = 4.2857 plugging this into the first equation and multiplying both sides by (-) -4.2857 = log T Take the antilog of both sides to obtain T The antilog of -4.2857 is 5.1795 x 10-5 Transmittance of light T to the eye is 0.000052 with an SN11 Welders lens. If your shade number (SN) is 11 then 11-1 = 7/3 OD. Please see this link: and assuming the formula are correct.(found in several locations) I have copied it here because I am new and it didn't get into the correct area. I posted a link with calculations and other links.

Solar eclipse glasses shade 14 welding glass lenses