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EOS R, EF-S Lens Crop Loss of Megapixels


I currently using a t2i Canon 18 mp crop sensor camera, According to Canon, when EF-S lenses are used on the EOS R camera the camera "will automatically produce cropped 11.6-megapixel images that match the smaller image circle of EF-S optics." So a 30mp camera effectively is now 11.6mp, much less than what I have with my current set up. I am looking to move to full frame so the EOS R seemed to be the way to go until I hit this stumbling block. I can't afford to buy both the camera and new lenses at the same time but plan to upgrade lenses slowly as budget permits. Is this something I should be concerned about or will having a better sensor and newer technologies make up for the loss in megapixels?


Dear @

I know that aperture values have nothing to do with the type of lens mount 😂

I was referring to the fact that the circuits of teleconverters (or speedboosters) act like a middle man, so the camera couldn't identify whether the lens attached is an ef lens or ef-s lens.


There is no middle man in an extension tube or in a reverse mount adapters, hence the camera will identify whether the lens attached is an ef lens or ef-s lens. 😉

i'm afraid a lens like 50mm won't be as good as a wider lens like 18mm in lens reverse situation.
I'll show you some results.

this is the maximum magnification of a canon 100mm macro lens (Not Reversed 1:1 magnification)
Normal 100mm macro LR.jpg





this is 50mm f/1.8 Full frame lens reversed ( wich was your sujestion)
50 Reverse LR.jpg




this is 18-55mm EF-S lens reversed @18mm

18mm Reverse LR.jpg



so, imagine the result of 10-18mm EF-S lens reversed @ 10mm





I have had my R for a year now the only issue I have now is the inability to use high-speed shutter on very few of my EF lenses. This was not known up front and all of the data states ef lenses were completely compatible if you use the Canon adapter. I have a lot of Canon ef L series glass and most won't work in high speed. They will all work on my M50 with adapter at 10fps...but my R that cost 3.5 times more can't...glad I kept the 80D and the M50 though I love the R this is my biggest issue.