Some good replies already. I think all current and most modern Pentax DSLRs have these settings.
Originally posted by bpv_UW - highlight correction - shadow correction - slow shutter speed/long exposure NR - high ISO NR
- highlight correction -
Off, except at certain light conditions. Have to develop a feel for it. Notice, if you enable this, you will not be able to select the lowest possible ISO (80, or 100, depending on camera), but the camera will still use it. It will use one ISO lower than what is displayed, and then brighten the image in post, while taking care not to burn the highlights. This function can be useful
- shadow correction -
Off. I think this one only affects jpegs, so if you shoot raw, you are just wasting processing power on in-camera PP for the jpeg thumbnail.
- slow shutter speed/long exposure NR -
On. Useful, unless you cannot afford the time between photos. Basically, if you take a 10sec photo, this NR will take another exposure after, almost as long.
- high ISO NR -
Off. Only affects jpegs, doesn't matter if you shoot raw. You can turn on some minimal settings, but I wouldn't give this much thought
Other options that only affect jpegs, but can slow down the camera because they require CPU power, are distortion correction, CA correction, vignetting correction, diffraction correction (latter two have been introduced to Pentax DSLRs relatively recently). Distortion correction takes the most CPU. If you shoot jpeg, I would turn all of these off. CA correction is the only one I might keep turned on, but there is really no need.
Of the listed options, the most useful one is Slow shutter NR, and then Highlight correction. At least, if you shoot raw.
However, if you shoot Jpeg, then you need to give each of these functions careful consideration, and decide whether you need it based on the conditions in front of you. Shadow correction can be useful sometimes, but can make photo look flat other times. Similarly for all other options; pros and cons