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<blockquote data-quote="Danno" data-source="post: 744872" data-attributes="member: 34269"><p>I just did a quick google search and the EPA said that the material was used in camera lenses from the fifties through the seventies. The best way to identify the lenses is that they will have a yellow tint to the lens that will darken over time having a negative effect on the images produced. A little fun fact from DP review...</p><p></p><p><em><span style="color: #666666"><span style="font-family: 'Roboto'">A radioactive lens that contains thorium will give off approximately 0.01 millirem (mrem) per hour. By comparison, a chest X-Ray gives you 1,000x that dose in a single shot (about 10 mrem). That means it would take you 167 days of using the lens for </span></span><span style="color: #767676"><span style="font-family: 'Roboto'">6 hours per day</span></span><span style="color: #666666"><span style="font-family: 'Roboto'"> before you've exposed yourself to a single X-Ray's worth of radiation.</span></span></em></p><p><em><span style="color: #666666"><span style="font-family: 'Roboto'"></span></span></em></p><p><em><span style="color: #666666"><span style="font-family: 'Roboto'"></span></span></em>The EPA was not concerned about the health risk either unless you were using an eye piece. </p><p></p><p><span style="color: #767676"><span style="font-family: 'Roboto'">https://www.epa.gov/radiation/what-kinds-consumer...</span></span></p><p><span style="color: #666666"><span style="font-family: 'Roboto'"><em>Older camera lenses: some camera lenses from the 1950s-1970s incorporated thorium into the glass, allowing for a high refractive index while maintaining a low dispersion. The health risk from using older camera lenses is <span style="color: #767676">low</span>; the radiation received when using a thoriated lens camera is <span style="color: #767676">approximately equal to natural background</span>.</em>​</span></span></p><p><span style="color: #666666"><span style="font-family: 'Roboto'"></span></span></p><p><span style="color: #666666"><span style="font-family: 'Roboto'">It is always a matter of choice but it seems that the lenses changed from thorium to other types of glass that were more stable. I know that does not completely answer the question, but it does give you a time line and a color to look for. As for me I am not one to chase after old glass that much, but if I did I am thinking I would not be as concerned, but that is me... I used to ride a motorcycle with no helmet.</span></span></p></blockquote><p></p>
[QUOTE="Danno, post: 744872, member: 34269"] I just did a quick google search and the EPA said that the material was used in camera lenses from the fifties through the seventies. The best way to identify the lenses is that they will have a yellow tint to the lens that will darken over time having a negative effect on the images produced. A little fun fact from DP review... [I][COLOR=#666666][FONT=Roboto]A radioactive lens that contains thorium will give off approximately 0.01 millirem (mrem) per hour. By comparison, a chest X-Ray gives you 1,000x that dose in a single shot (about 10 mrem). That means it would take you 167 days of using the lens for [/FONT][/COLOR][COLOR=#767676][FONT=Roboto]6 hours per day[/FONT][/COLOR][COLOR=#666666][FONT=Roboto] before you've exposed yourself to a single X-Ray's worth of radiation. [/FONT][/COLOR][/I]The EPA was not concerned about the health risk either unless you were using an eye piece. [COLOR=#767676][FONT=Roboto]https://www.epa.gov/radiation/what-kinds-consumer...[/FONT][/COLOR] [COLOR=#666666][FONT=Roboto][I]Older camera lenses: some camera lenses from the 1950s-1970s incorporated thorium into the glass, allowing for a high refractive index while maintaining a low dispersion. The health risk from using older camera lenses is [COLOR=#767676]low[/COLOR]; the radiation received when using a thoriated lens camera is [COLOR=#767676]approximately equal to natural background[/COLOR].[/I]​ It is always a matter of choice but it seems that the lenses changed from thorium to other types of glass that were more stable. I know that does not completely answer the question, but it does give you a time line and a color to look for. As for me I am not one to chase after old glass that much, but if I did I am thinking I would not be as concerned, but that is me... I used to ride a motorcycle with no helmet.[/FONT][/COLOR] [/QUOTE]
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