[MikeStnly]

I couldn't find this in a search, although the questions is asked about the 645Z.

But I am reading this "The native ISO will vary from camera to camera and may not necessarily be the lowest ISO setting available. Selecting an ISO lower than the native ISO will involve a reduction in gain, which in turn limits the performance of the sensor capture and means you are capturing at a reduced efficiency." The full article is here https://www.amateurphotographer.co.uk/technique/camera_skills/how-to-achieve...-photos-157466

So, does anyone know what the native ISO is on the K-3iii.

Thank you.

[C_Jones]

I have read that the K-3 III has a native ISO sensitivity of 100 to 1600000.

[MikeStnly]

I have read that the K-3 III has a native ISO sensitivity of 100 to 1600000.

Interesting, but would it not be only one number? Say, ISO 200 for example. The article seems to say that if you then shoot above or below that ISO that gain is either added or removed and this would have an impact on the exposure.

[FozzFoster]

Maybe they are referring to 'base iso' which would be 100 for the K-3 Mark III.
For example, my K-5 has a base iso of 100 as well, but you can select a setting to 'extend' the iso down to 80.

[gatorguy]

I seem to recall the native ISO as being 200.

[C_Jones]

Interesting, but would it not be only one number? Say, ISO 200 for example. The article seems to say that if you then shoot above or below that ISO that gain is either added or removed and this would have an impact on the exposure.

I was thinking about that too, and have seen something similar to what you are expressing about the quality of shooting at, above, or below the one iso discussed before. As a general guideline for myself, if I can I shoot near 100 or 200 I am satisfied, and I sort of assume that 100 is the best I can do. But as you are probably curious about, there may be more information pertaining to it that I may possibly not know. As FozzFoster mentioned, the 80 iso may be a choice in some cases also, which I sort of recall being available in some of Pentax image data.

[MossyRocks]

I would think it would be 100 and 640. My understanding is that it has 2 base/native ISOs with one at 100 and the other at 640. I say this because I seem to remember reading about the sensor it uses and at ISO 640 it goes into a different mode. I seem to remember reading about this in looking at some detailed info about an astro cam that also uses this sensor. It isn't like using the expanded ISO of Nikons where there is the odd ISO 31 or what ever it is where it basically clips the highlights. Having the K-3iii and K-3 I have been really impressed with how clean the images are from the K-3iii and will basically shot so that I don't clip the highlights and if I think I might have will check the histogram and adjust from there.

[MikeStnly]

"Despite the crop-sensor, the K-3 Mark III offers an incredibly expansive native ISO range. No expanded ISOs here. The K-3 III offers a base ISO of 100 and a high ISO of 1,600,000. " from Pentax K-3 Mark III First Shots: Sample images from Ricoh’s long-awaited flagship APS-C DSLR (UPDATED)

So, 100 is the base but is it the "native"? It would be interesting to do some pixel peeping at 100 and 640 as MossyRocks indicates.

[Mooncatt]

I would think it would be 100 and 640. My understanding is that it has 2 base/native ISOs with one at 100 and the other at 640. I say this because I seem to remember reading about the sensor it uses and at ISO 640 it goes into a different mode.

I think ISO 640 is where the accelerator unit kicks in. It's supposed to offer faster/better noise reduction, and I think is forced at that point. Even affecting RAW files.

[snappyhoffy]

I think ISO 640 is where the accelerator unit kicks in. It's supposed to offer faster/better noise reduction, and I think is forced at that point. Even affecting RAW files.

Certainly does a good job!

[mir]

I think ISO 640 is where the accelerator unit kicks in. It's supposed to offer faster/better noise reduction, and I think is forced at that point. Even affecting RAW files.

Native ISO is the sensors sensitivity to light without the need for software corrections/help. So shooting outside of the native ISO range increases noise dramatically. Some manufacturers divides in native ISO and extended ISO (like optical zoom versus digital zoom - digital zoom is software enhanced zoom). Since I have not been able to find anything indicating differently I guess the ISO ranges for every Pentax body is also its native ISO range. So Pentax K3iii is a beast compared to its nearest competitor Nikon D500 -> Pentax K-3 III vs Nikon D500 Detailed Comparison 100-1600000 vs 100-51200. That does not mean that I recommend shooting with ISO higher than 12800-25600 and for pictures for printing ISO <= 3200 would be my recommendation. But as always YMMV

[gatorguy]

I think ISO 640 is where the accelerator unit kicks in. It's supposed to offer faster/better noise reduction, and I think is forced at that point. Even affecting RAW files.

The accelerator begins to kick in after ISO160, the K3III's "native" ISO from what I can determine, so for practical purposes from 200 and up.

[kypfer]

It would seem I'm not particularly sensitive to noise and will happily use most of the five-figure ISO ratings offered by my K-3iii without thinking about it, but what I have noticed, on the KP when making star-trails, that at ISO 800 and above the noise-reduction feature kicks in and causes gaps, so ISO 640 may well be the highest speed that Pentax consider to be acceptably noise-free on that camera.
I've yet to try a similar exposure using the K-3iii.

[MossyRocks]

I think ISO 640 is where the accelerator unit kicks in. It's supposed to offer faster/better noise reduction, and I think is forced at that point. Even affecting RAW files.

I was aware of that but I think with the sensor there is something else that happens at ISO 640 as well. I could be wrong or misunderstanding something but I thought there was something else going on at 640.

[EssJayEff]

On a related note, I think the K-3 III has ISO invariance.