Originally posted by Nicolas06 One must understand that officially support FF lenses have a specific name like DFA or FA. While a DA might look to work on a film body or without contact on a digital FF body, it doesn't mean that once really connected to an hypothetical FF body it would not be recognised as an APSC only lense as officially said by the specifications.
I would add that there is no FF out right now in K-mount That it has been something like 10 years some say that the FF is for "next year" and Pentax explain they study the market and will do if they see the conditions for it. So maybe they see the camera market is shriking right now (it does shrink heavily in fact), or they see new sensors technology that make FF completely useless (much more dynamic range/high iso perf), maybe the priority is more to serve the demand of 645 where they have the market for themselves or maybe they decide to stop investing...
Whatever is decided, anybody really interrested on FF should not buy a lense branded and labelled as optimized for APSC. More anybody that want to go for FF should consider Pentax really consciously until an actual FF model that fit their needs is actually released.
Having a different behavior is just a receipe for a big disapointment.
I am aware of the Pentax nomenclature - FA, DA, DFA.
To clarify, I wasn't suggesting that one should plan for a yet-to-be-introduced Pentax FF system, and on that basis purchase the DA*200.
Rather, purchase it fully intending for APS-C use, but be aware that this DA lens (and several others too) has the added "bonus" (advantage) of an image circle which supports FF dimensions, when that possibility appears.
Of course, in FF use, the FOV would become like 135mm in APS-C, as per the DA*50-135.
Or put it another way, those who use a film/FF DSLR body with a 70-200 f2.8 zoom will be familiar with the 200mm FOV.
Interesting to note that while there may possibly be issues in using a DA lens on a FF body, the same is true for the reverse case - using an FA lens on an APS-C body.
Today we do this all the time, eg with the FA Limiteds. In so doing, we suffer the "purple fringing" phenomenon. FA lenses were meant for film, and can cause purple fringing on digital sensors - so I'm given to understand. (In fact, if I understand right, one of the design aims for DA series lenses was to solve/control this issue.)
But that doesn't put us off using FA lenses on APS-C. So it would be really great if certain DA lenses could work on FF - just think of it as a bonus, not a "guaranteed thing". There may be limitations, but if one uses it with understanding, and to the extent possible works around the limitations, it could open many new dimensions to explore...