Originally posted by BigMackCam We're all different in our requirements. A huge number of my shots are taken between ISO 1600 and 6400. Some, higher still. My single biggest requirement from post-processing software is effective colour noise reduction at higher ISOs. After that, it's shadow and highlight recovery. Given that, I'll
never be fed up with improvements in detail, noise and dynamic range at higher ISOs.
Photography may be the light, but often there's simply not enough of it. Shooting at f/1.4, or with long exposures, just isn't viable for certain types of shot. Often, you need a reasonably high shutter speed to capture movement, or you need f/8 to get the required depth of field. Occasionally, you need both. In lower light, that means high ISO.
Your use cases might not require more than ISO 400 most of the time, but as I said, we're all different
Exactly!
If you look at the full cube of possible exposure settings: {shutter speed} X {aperture} X {ISO}, there's good reasons to use every bit of it.
In some cases the best shutter speed is very slow (waterfalls, star trails, ghostly people), some cases it's a fast as possible (hummingbirds), and some cases it's a very specific value (e.g., something like 1/100 or 1/200 for airshows to stop a flying aircraft but let the propeller blur).
In some cases the best aperture is very wide (f/1.4 for super shallow DoF), some cases it's very narrow (f/32 for macro where the extra DoF is worth the diffraction), and some cases it's a very specific value (e.g. an f/8 sweet spot or a specific hyperfocal aperture).
Unlike shutter speed and aperture the "best" ISO (the ISO that a photographer would love to use if lighting weren't an issue) is the lowest ISO. Unless the photographer loves grainy pictures (which can always be created in post-processing), there's every reason to use the lowest possible ISO. But if the photographer has already dialed in the best shutter speed and the best aperture, then the lighting conditions (and exposure compensation settings) pretty much force them to use a certain ISO which might be quite high (especially at night, indoors, in macro, or with fast objects).
I think I've used pretty much the entire exposure cube from slow-shutter blurred daylight images to fast-shutter moon-lit images and from wide aperture shallow DoF to super narrow aperture macro. And I've used every ISO on the dial because half the time (and in many places), it's really dark on Earth.
That brings up the issue of compromise in photography and the cost to the image's quality or meaning caused using a different shutter speed, aperture, or ISO than the "best" ones. Here the biggest issue is about the highest acceptable ISO and being forced to compromise on shutter speed or aperture to avoid high ISO. Being forced to use a slower shutter speed than the best one to avoid a high ISO is a compromise. Being forced to use a wider aperture than the best one to avoid a high ISO is a compromise*. Sometimes the photographic conditions are not ideal which means deciding between a substandard photo or no photo at all.
What's interesting about the K-1ii is the addition of the accelerator and noise reduction technologies pioneered in the KP. Those technologies seem to have the potential to "clean up" the image by maybe 1 stop possible 2 (if the the ISO 819200 on the K-1ii is equivalent to ISO 204800 on the original K-1). And that really is a meaningful upgrade because it reduces the percentage of photographs that can't use the best shutter speed and best aperture because those best settings require a "bad" high ISO. Simply put, cleaner high-ISO means more and better images.
Personally, I prefer cleaner images to either more megapixels or more fps but that's just me.
(*NOTE: the aperture-ISO issue is also an AF issue. AF accuracy does not need to be as high with narrower apertures afforded by a camera with clean high-ISO capabilities.)