  A list of accepted focussing screens is given, but the Ec-S high-precision one is not among them.  If it has been desupported, that would be a real step backwards. Users of fast manual-focus lenses in particular would have a problem; with back-button autofocus set, you'd need to hold the AF button down to get focus confirmation. Users of lenses via unchipped adaptors would be in real trouble.  A list of accepted focussing screens is given, but the Ec-S high-precision one is not among them.  If it has been desupported, that would be a real step backwards. Users of fast manual-focus lenses in particular would have a problem; with back-button autofocus set, you'd need to hold the AF button down to get focus confirmation. Users of lenses via unchipped adaptors would be in real trouble.  A list of accepted focussing screens is given, but the Ec-S high-precision one is not among them.  If it has been desupported, that would be a real step backwards. Users of fast manual-focus lenses in particular would have a problem; with back-button autofocus set, you'd need to hold the AF button down to get focus confirmation. Users of lenses via unchipped adaptors would be in real trouble.  It's not supported at this point, although the only problem it causes is with metering (physically, it fits). Chuck Westfall told me that it's apparently something Canon could fix in firmware, if they choose to.  It's not supported at this point, although the only problem it causes is with metering (physically, it fits). Chuck Westfall told me that it's apparently something Canon could fix in firmware, if they choose to.  