Originally posted by Uluru I know. Thanks for that.
But I was writing about dedicated optics, not crop inside the camera.
Crop is an afterthought. It is easy and is not a solution but hindrance — only so much cropping is possible.
Same would be that Pentax comes with 3 lenses, one wide, one normal, one tele — for its entire DSLR line — and leaves you then to "crop" other focal lengths.
Real dedication and vision are properly designed lenses and adapters, which can utilise entire sensor area.
Would not any number of those 1.5x and 2x teleconverters with 49mm or 52mm filter rings work? The GR adaptor has a 49mm thread, correct?
They are dime a dozen on ebay. More often than not they come packaged with a wide converter and a stack of macro lenses.