[slackercruster]

Do any of the Pentax dslr's have long exposure noise reduction?

[mattb123]

My K-5 and K-x both do. Exposures > 30s do a dark frame subtraction by default.

[jezza323]

My K200D has it, optional of course

[D0n]

might also consider doing a multiple exposure for some subjects.... you'd be surprised at the results...as far as noise reduction goes...

[RioRico]

K20D, for sure. Heck, even my old Sony DSC-V1 P&S has DFS.

[slackercruster]

Why would it be optional? Isn't low noise best?

[Stone G.]

Why would it be optional? Isn't low noise best?

No, not always. Imaging you are photographing fireworks, lightning, meteor trails or stars. Often you will have your shutter open for several minutes - and then you will have to wait the same several minutes before you can open your shutter again, because that's how DFS works. It is much more efficient to take a few dark shots (with lens cap on) at the end of the session and the do the subtraction in software at a later time.

As an astrophotographe, I am very happy that Pentax has made DFS optional on my *ist DL, K200D and K-5!

[smigol]

It's also optional on the K10D.

There's a statistical advantage of doing a separate dark subtraction. Ideally, you'd want to average the noise profile of bias and dark signals so that the true noise profile is removed and not cluttered by outliers like cosmic ray hits, etc. By collecting a library of dark frames at a range of temperatures, you can create a good noise profile for the camera.

With using in-camera DFS, there's only one dark frame per light. This presents a small risk of adding random noise to the file.

Granted, time-shifitng the DFS to a separate process does require a lot of "at home" time and post production to create a finished shot.

[Wheatfield]

I'm pretty sure they all do, though I could be wrong about the original 6mp ones.

[StephenHampshire]

I'm pretty sure they all do, though I could be wrong about the original 6mp ones.

K100D certainly did