[WillCarney]

I did notice in a few other threads about the DFS in Pentax digital cameras.
I recently had to return a K200D because the DFS just took too long in time
exposures (over 30 seconds).

Is it true that all the Pentax digital SLR's don't have a disable function for DFS?

William

[Eruditass]

K200D and all CCD sensors can completely disable DFS, iirc..

Pentax CMOS cameras can only disable it up to 30s at the moment, even though say the K-x is excellent with regards to dark frames:

https://www.pentaxforums.com/forums/811084-post43.html

Hopefully they will add that feature in firmware. So far, some people have been getting around it by stacking 30s frames and multiple exposures, which isn't quite ideal:

https://www.pentaxforums.com/forums/809949-post26.html

[wildlifephotog]

Both noise reduction settings can be turned off on the K200D. Page 85 of the manual.

[wildlifephotog]

Actually stacking is very useful. You can greatly improve signal to noise ratio that way, especially at high ISO.

[Eruditass]

Definitely, I was referring to ease of taking pictures. DFS improves SNR but requires more time, especially if the camera makes you do it after every shot. Stacking requires some time at home.

[wildlifephotog]

Well for astro work, stacking is the only way to work with digital. I never use any noise reduction in camera.
I've never tried stacking other kinds of photos.

[WillCarney]

Thanks for the quick replies.

I read the manual several times, must have missed page 85 or just read past it
too fast. Well the other reason to return it was the controllablity issue.
I need to be able to control the camera functions at the computer.
The less the telescope camera system is touched the less the vibration.
Most of my astrophotography runs between 5 and 30 minutes autoguided
so mirror lock up and controllability is a must besides turning off DFS.

I have had some bad luck with CCD astro cameras and am looking into
digital cameras. Looks like I will have to go to Canon or Nikon. Pentax just
does not have it. If I purchase another brand I will be dumping my Pentax
stuff all together despite 40 years of using them.

William

[wildlifephotog]

There are a dozen or more very good astro digital cameras available. A few are even comparable in price to a K7.

[pti-andy]

Thanks for the quick replies.

I read the manual several times, must have missed page 85 or just read past it
too fast. Well the other reason to return it was the controllablity issue.
I need to be able to control the camera functions at the computer.
The less the telescope camera system is touched the less the vibration.
Most of my astrophotography runs between 5 and 30 minutes autoguided
so mirror lock up and controllability is a must besides turning off DFS.

I have had some bad luck with CCD astro cameras and am looking into
digital cameras. Looks like I will have to go to Canon or Nikon. Pentax just
does not have it. If I purchase another brand I will be dumping my Pentax
stuff all together despite 40 years of using them.

William

The K-x works quite well in "bulb" with the IR remote now that it is a toggle on/off so there is not as much of a need for remote computer control. Mirror Lockup is also supported with the timer+3s mode. It basically will throw up the mirror and then wait 3 secs before opening the shutter.

The only real issue that remains is the DFS. I've been quite successful using multiple 30s exposures with the K-x due to the fact that it has a two stop improvement in noise over the CCD Pentax DSLR's.

I think somewhere between 30s to 5 minute exposures are possible however, most DSLR's don't like much longer than this because the sensors are not cooled. If you really don't want to stack multiple photos and need 30 mins of exposure time then no DSLR is for you and you should only be looking at dedicated astro cameras. You will pay much more money for these or the sensor sizes will be smaller. I have an Orion Starshoot pro I'd be happy to sell you simply because I get better results with the K-x and stacking.

I truely wish Pentax would allow DFS to remain off, as the menu setting implies, for any duration exposure. It should be up to us to decide this, after all, that is why the menu option is there and is defaulted to "on".

This is a very hot topic for both the K-x and K-7 and I read on one of the other threads that Pentax responded to a user and said they would recommend this change for the K-7 in the next firmware release. Not sure if that would really happen but if they can do it for the K-7 then they can do it for the K-x as well which is actually more capable for low light anyway.

Maybe we should all send an email to Pentax requesting this and if they get enough response they might do something about it.

-Andy