I do not own a K-5, but I have a K-30 which has the same sensor as the K-5 and therefore the same noise level, but a lower dynamic range (its minimal sensitivity is 100 ISO and its raw are on 12 bits). I also own a K-70, but unfortunately I bought it to replace the K-30 that died. So I was not able to make a direct comparison.
I find the noise of the K-70 much more bearable: It has a grain-like texture, finer than on the K-30, and much less chromatic noise. But it has a little more "salt and pepper" noise. The very high sensitivities (> = 3200 ISO) are much better but you do not seem interested by the very high sensitivities
I can not stand the high light burned, so I tend to underexposed the photos and to catch up at the developement. The K-70 is still very good at this level (better?)
For medium sensitivity (800-3200 ISO) I would say that given the finer noise structure, the much lower chromatic noise level, and the greater number of pixels, we gain about 1 EV compared to the K-30. You can use this great tool for comparaison. (They have not K-5/K-30, but K-50 who has the same sensor) :
Image comparison: K-70@3200 vs K-50/K-500/K3@1600 (dpreview)
(In raw, because in jpeg the K-70 is light years ahead of the K-30 / K5 because it does not have this anti-noise with plastic look)
For the dynamic range you can look at the bottom of this page to "Raw DR: Exposure Latitude" and "ISO Invariance" :
Shaking up the market: Pentax K-70 Review: Digital Photography Review
the K-70's performance is among the best of the APS-C sensors (unfortunately there is neither K-30 nor K-5 in this test to be able to compare)
At this site¹, they measured the total dynamic range (SNR = 1) of the K-70 at 100 ISO at 13.5 EV, practically the maximum possible in a 14-bit file, and 9.2 EV for DR with low noise (SNR = 20). By comparison, they had measured the total dynamics of the K-5 at 80 ISO at just over 12 EV and DR with low noise (SNR = 20:1) at 8 EV for 80 ISO, and 7.7 EV for 100 ISO, so that the K-70 gain by 1 - 1.5 EV compared to K-5. These differences seem excessive for me, but in any case the K-70 should not have a lower dynamic.
¹
Optyczne.pl Test Pentax K-70 : Gamme et dynamique tonale Optyczne.pl Test Pentax K-5 : Gamme et dynamique tonale
(The site is in Polish. I read it translated in French via Google translate, it is just readable, but very interesting).
But does not expect too much improvement on the noise side or DR (except for very high sensitivity). The really cool thing is the more resolution combining 24 Mpix sensor, no low-pass filter, and Pixel Shift Resolution. This is wouah... For some statics subjects, it has the same details level (and perhaps more) than a 36 Mpix Full Frame or even a 42 Mpix. And a lot of less artefacts
Image comparison: Pentax K-70 vs Nikon D810 vs Sony Alpha 7RII vs Phase One IQ180 (dpreview)
You must use the 100 Mpix IQ180 to see again the vertical lines at the top left. This improvement is even more obvious with color resolution, something which is very hard form the bayer matrix.
Image comparison: Pentax K-70 vs Nikon D810 vs Sony Alpha 7RII vs Pentax 645Z (dpreview)
(unfortunately they have not tested the PSR function of the K-70 in raw).
This is quite of-topic, but i think it's worth mentioning it.
My life: I have a little baby that I keep the day, and in the evening I work in a cinema. I have no time to develop my raw! I quickly develop them in the K-70, and so I have not got much experience in developing K-70's raw files . What I can say is that the jpegs are much much better than those of the K-30 for ISO 800-3200.
Last edited by gnujsa; 09-17-2017 at 03:10 PM.
Reason: screenshot now in the post