Originally posted by mccririck I guess the important thing is not to look into the lens close up. Don't hold it up to your eye and stare into it!
Has anyone measure the radiation from the front of the lens, from the rear, from the sides, and then from the rear when it is attached to a camera? It would be interesting to see the differences.
Here's a scientific study that explains how small the level of radiation from an average thoriated lens is:
http://www.diva-portal.org/smash/get/diva2:652338/FULLTEXT01.pdf
This topic has, of course, been beaten to death in this forum over the years. See, for instance:
Radioaktiv Lenses - PentaxForums.com
Or;
throium glass lenses - PentaxForums.com
If you were to spend a thousand hours per year looking through your camera lens (that's 2.73 hours per day, every day of the year, or, 19.23 hours per week) you would be exposed to a total of 0.2 mSv/yr. That is the equivalent of about 5 or 6 intercontinental flights a year or 2 chest x-rays. One CT-scan is 20mSv, so you'd have to look through your lens for 10,000 hours (There's 8,760 hours in a year) to get the equivalent exposure as to one CT-scan.
Your normal background radiation exposure, in the USA, averages 6.24 mSv per year. If you use your lens for 24 minutes every day, your annual exposure would increase by about 0.5%.
Put another way: If you have granite benches in your kitchen, your annual exposure will be somewhere between 0.005 to 0.18 mSv depending on the type of granite, if you spend 4 hours a day in the Kitchen. It could be argued that going outside and taking photos will be safer for you than spending time in your kitchen.