Do I switch to another brand?

Sorry to drag this on but .... I’m going through the same personal crisis. Rather than start a whole new thread, so I’ll tag onto this one, if it’s okay.

I love my K3-ii to photograph mostly sports and motor racing. I have been dithering about getting the K-1 mostly because the frames per second is much slower than the K3. I’m not going to rehash the same concerns about lenses and so on.

I’m happy to continue with Pentax. I still have my old Pentax ME Super. If I can squeeze another year or two out of my K3 I would be happy. However, it’s becoming increasingly more difficult to buy Pentax gear in Australia so may have to cross over anyway.

My question is this; I would like to know what the experience has been using full frame lenses on the aps-c body.

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Not that I have much experience in this field with the exception of the D-FA 100mm WR Macro and legacy/film lenses on a K-70 but they performed very well. I don't think there's ever much issue discussed with FF lenses + APS-C body, but APS-C lenses on a FF body is fairly well documented with respect to vignetting etc.

The FF lenses are fine when used on the APS-C bodies. They are not even overly large in most cases.

Thanks