I don't think the extender does any magnification. In fact, it reduces the magnification. On a full frame camera that is no big deal. On a crop format camera it is. It is hard enough to see the viewfinder as is, but by reducing it even further, I would think it would make it much harder to focus. My friend with the 5Dm2 has one. It lets him see the full frame with his glasses. As I stated previously, when he tried my Nikon magnifier, he could not see the full frame with his glasses. I did not try his extender on my Rebel. Read the reviews at: http://www.amazon.com/Canon-EP-EX15-Eyepiece-Extender-Cameras/dp/B0000AQI9E Look around on Google. The purpose is for eyeglass users to see the whole viewfinder. It reduces the image by 30%, so if you are looking for a focusing aid, this is not what you want. Aram From: Dave Tang Sent: Saturday, August 01, 2009 5:20 PM To: leicareflex@xxxxxxxxxxxxx Subject: [LRflex] Re: Summicron 50mm take apart? Guys, try the eye piece extender for Canon. It helps me to see the full frame on my 5Dm2 and focusing on my Leica R glasses with adaptor is a lot easier. It's a cheap $10 modification so no harm trying it. My cheap China AF confirmation chip is pretty fast even without stopping down. I got a 35 n 50 crons f2 and a 50 luv f1.4 -------------------------------------------------------------------------------- Share your memories online with anyone you want anyone you want.