Originally posted by sbh I think Pentax naming is not well ordered. If only the 645 and K-7, K-5, K-3 and K-1 then it would be ok. But what is the KP? and is the K-70 the lesser model of the old K-7? I find it confusing. Either make it a proper order or give them independent names without any order.
I don't think it's not well ordered.
645 has always been a medium format and sits solo.
K-7, K-5, K-3, K-1 are all pro grade due to the single digit naming (7, 5, 3, 1). As you go up in number (7 being low, 1 being the highest), you go higher in the lineup.
K-P, just like the K-S1 and K-S2, are "test beds" for new ideas, the ideas that work and take off from these get implemented into other cameras (Lettered names have been this way since the K-Sx series). For example, flippy screen, led lighting, Native WiFi, NFC, and Smartphone control).
K-70, just like the K-30/K-50 and K-500 are the entry level into the Pentax lineup (double digit and higher). Read it like a scale (keep the year of release in mind). 5XX, 5X/3X, 7X, 7, 5, 3, 1.