Im I misreading ??
With adapters we will have a crop factor ??
so for example a 100-400 is really going to be a 120-420 ??
Did I read that right
The linked article in Mark0159 post 436 was quite informative!
The adapters themselves do nothing to switch crop factor. They merely allow the 44mm backfocus EF lens to be mounted on EOS R body with full functioning without loss of performance, Crop factor switching is with video (vs. still), or with EF-S lenses. No details about how the camera knows to switch to crop mode (for EF-S lens smaller image circle, nor details about how aftermarket lenses with smaller (crop) image circles are handled.
But in addition...
- EF/EFS lens can be mounted on EOS R body with full functioning without loss of performance
- EF/EFS mount lenses can be used with the EOS R style control ring on the control adapter
- EF/EFS mount lenses can be used with an in-adapter filter
Even without any adapter, the EOS R lenses have higher speed communications between body and lens, and the EOS R body can perform some of the IS corrections in conjunction with in-lens IS corrections (Canon new patent that was filed in late 2017 and approved in early 2018)
Interestingly the EOS R can perform image quality processing tasks to further optimize IQ, but these can only be done
on JPG files stored in EOS R camera
RAW files if used in conjunction with Canon's DPP software