Home is where the heart is.
I plan to use it on 350D, which I believe the viewfinder is small, about 87%?
So actually 1.35x will enough already, no need magnifiers like 1.7x?
This was copy from B&H website.
The Canon EP-EX15 Eyepiece Extender extends the eyepiece by 5/8" (15mm) from the camera body and reduces the viewfinder magnification by 30%.**This is useful for eyeglass wearers and others who wish to prevent the tip of their nose from touching the camera body.**It also prevents condensation or fogging.
The EP-EX15 fits all Canon EOS cameras except the EOS 7D, 1D Mark III, Rebel T1i, A2, A2e, 3, 5 and Elan II-7N series.