EOS 3 diopter eyepiece question

[mids1999]

Can someone please help me with diopter eyepiece choice for the EOS 3?

I recently picked up a Canon EOS 3 for a film photography course at my local college. Before that, I was shooting digital with a Canon Rebel XTI.
On the Canon Rebel XTI, I was able to get fairly clear vision through the eyepiece with the diopter adjustment set to the maximum - position --could be slightly better with slightly more - diopter. I read that this is -3.0 diopter on the Canon Rebel XTI.

I would like to get similar results from the Canon EOS 3 eyepiece but I read that the Canon EOS 3 has built in -0.5 diopter.
Can someone please tell me how the -3.0 diopter ED eyepiece would calculate with the built in -0.5 diopter of the Canon EOS 3?
Would the Canon ED -3.0 eyepiece be a -2.5 eyepiece, which when added to the built in -0.5 diopter makes a total of -3.0 diopter, or would it be a true -3.0 diopter eyepiece, which when added to the built in -0.5 diopter makes a total -3.5 diopter?

 

[ic-racer]

If it is anything like the Nikon system, they factor in the built in diopter to what is marked on the replacement diopter lenses. The time you need to be concerned with this is when using the replacement diopter lenses on other cameras. So, I'm going to say the Canon -3.0 is really a -2.5, and works as a -3.0 when you put it on a Canon.

 

[mids1999]

After ordering and having my order cancelled due to unavailability, I finally obtained my eyepiece.

I have another question for anyone familiar withh the system.

Can the diopter eyepiece ed, and and large eyecup ed-e be used together?