Originally posted by janosh I find no "little green light" at bottom of K70 viewfinder. Just an occasional tiny hard-to-see red blip in focus area.
I'm only using "A" versions of Pentax 28/2.8 and Pentax Macro 50/2.8.
See the right-hand side of p18 of the user manual, available here
Operation Manuals Download : Support & Service | RICOH IMAGING and check item 8, focus indicator, and subsequently on p47 for the "Green Hexagon" … it's been a feature of Pentax DSLRs since the beginning.
I became familiar with it on my *
ist film camera … it's "different" and needs a steady hand to keep it lit, especially with a wide-aperture lens, but it really does work very well.
You should have little trouble using a 28mm f/2.8 … a 90mm f/2.5 needs a light touch, but is perfectly usable with practice
Try it with the camera on a tripod to help realise how fine an adjustment it is
Remember, unless you're working at maximum aperture, there'll be a little "wriggle room" at actual exposure time from the depth of field introduced when the lens stops down.
Do recognise that the red light that illuminates is only an indication of which focus point is being used, it's not a confirmation that the lens has actually focussed!
Enjoy!