Originally posted by gbeaton What makes the K3 another grade above the K5... and don't say megapixels.
Getting back to the OP's original questions "Why is it the K-3 and not the K-5III?
Why not? When Pentax revamped their flagship cameras, the K10D and K20D, with a new body, new sensor, more megapixels and several other new/upgraded features, they didn't call it the K-21 or the K20DII, they called it the K-7.
When the exact same K-7 body was upgraded with (2) more megapixels, a different sensor and other features, it didn't become the K-7II, it was the K-5.
While the K-5II and IIs are upgrades to the K-5, it is the same body, sensor and most features. The removal of the AA filter applied only to the K-5IIs, otherwise the two cameras are based about 90% on the classic K-5. Hence, it became a 'series' upgrade.
Now, we have an entirely new body, a unique feature that allows AA or AA-less shooting, a whopping 50% more megapixels, using yet again a different sensor (yes, I'm deliberately disregarding your admonition to 'not say more megapixels'. 16Mp compared to 24Mp is not something you or anyone else can blithely wave away because it's inconvenient to your premise), and a list of other new, upgraded and upper-tier functions, much too long to list here.
Many of those improvements have long been clamored for by the Pentax faithful. Regretably, the flash-sync speed wasn't one of them, but otherwise this appears to be not only a new model, but a new generation of flagship camera body.
Can you supply any rational reason WHY they would call this camera the K-5III?
If so, we're all waiting to hear it.
Ron