Pentax K7 Noise Reduction

My recent attempts to take star photos during night with long exposure(bulb) was OK.But the problem is ıt was not possible to switch off the "Noise Reduction" function.Among the K7 camera menu items under the tab "c" #18 and #19 are for Noise Reduction.I have changed these values from 1(which are factory values) to 2 and 4 to swich off to NR function but it doesnt function at all.
If somebody could help me how to escape "Noise Reduction" when it is required
Regards.


I.Erturk

Could you be a bit clearer ... that is, what displays on the LCD menu when you change the values, what is the description of that item that is displayed? And how do you know (from the photo taken) that 'it doesn't function at all' ? Do you mean that NR remains on when you want it off?

There is another setting for NR, that controls the ISO range that the NR operates in - if you're shooting at ISO 100 it may not be operating anyway. I think this function is actually the 'Dark Frame Subtraction' feature, not really noise reduction as we think of it on a computer - is that right ? I think its 'Long Exposure Noise Reduction' which is really Dark Frame Subtraction. It only kicks in if the range is set and you're within the ISO range set, and the exposure is long.

Yes you are right.There are three relevant items for NR.
But I did not mention the one Item #20. Since No 1 is choosen for that item as factory value and I did not changed that option at all.In case of 1 is selected which mean "noise reduction is activated when ISO sensitivity is set to higher than 800". I never used ISO value higher than 400 during my studies.
To be more clear: when item #18 is selectred as 2 means:"noise reduction will not activate when using a slow shutter speed" is the explanation what I see on LCD screen.In case of item 19 is selected as 4:the explanation on the screen"noise reduction will not activate when using a high ISO sensitivity."
I dont know about 'Dark Frame Subtraction' feature.But what happens after long exposure (for example 30 minutes) ended by me, K7 still works for about another 30 minutes(some noise inside the camera)and camera is not ready to take another photo during this time.
I hope I am clear enough.
Regards.

turn slow shutter speed noise reduction OFF. if you are doing star trails select continuous shooting ,shutter speed 30sec. aperture f5.6, ISO 200, lock the shutter open with remote , no noise problem this way. if you are after a static shot of the night sky i have no idea what the settings would be but someone on here will know but i am sure the NR is off and done in pp with software.

I think there's confusion over the termonologies ... Noise Reduction 'as we know it' is (as redbusa99 says) done in PP on the computer. This is the only intelligent approach really, because each image has different NR needs, and may not need it all over, so selectively is the best way.

'Noise Reduction' on the K7 camera (and later models also I'm guessing?)is not 'NR as we know it' .... the camera NR technique and process is 'Dark Frame Subtraction' - I don't know the science behind it (others will I'm sure), but it involves taking an extra exposure, with the shutter closed I think, so that the extra exposure records a 'noise map' of the dark (a dark frame) ... this is then used to 'subtract' the noise from the actual image exposure.

The settings available are to control at what ISO it starts to function. The last time I did bulb shooting I was only using 30-45 sec exposures, and the camera was remaining locked while it took the 'dark frame', so I was waiting twice the time for a single shot (I could hear the shutter close in between). Now my NR settings on the camera are set to kick in at ISO 400, and I was shooting at 100, so it seems that Dark Frame Subtraction functions automatically for any long exposure ?? We may not be able to prevent this - but surely it is a good thing anyway, I don't think you should want to de-activate it (can't imagine the results without it!). Because its not blurring type Noise Reduction then I don't think it has a negative impact on image quality.

I appreciate you need to use the camera again, and 30 minutes is a very long time!. But I wonder , would your images be usable without the Dark Frame Subtraction?

In the K7 you can not turn off long exposure NR, or dark frame subtraction to give it its proper name.

Hi bettyswolloks and everyone who joined to this discussion,
I think that is the case as Bettyswolloks has put it;
Using pentax K7 it is not possible to switch off the Noise Reduction future although in menu items it is exist.
I think it is very strange having such menu items for K7 as if switching off Noise Reduction is possible but in fact this is not the case.
Thanks for everyone for the contribution.
Regards.

item 18 custom menu ,page 92 of manual , slow shutter speed NR on or off

That only effects slow shutter speed. For speeds longer than a few seconds Darkframe Subtraction kicks in.

That was my experience - despite having the start point for NR set higher, I still had to wait for the extra 'dark frames' to record each time on exposures of 20-45 seconds.

What about my question above on the need for this ? Am I right in surmising that Dark Frame Subraction is NOT a feature that we would want to turn off anyway, in any long exposure situation?

turns off up to 30sec apparently but not in bulb mode, i.e over 30sec.

OK, thanks, that makes sense. But what would be effect if it was turned off for these long exposures - would it make the images unusable? I'm still working on an assumption that in fact our OP should not really be WANTING to turn it off ?? My own fairly recent shots using it, (the night Canary Wharf buildings) were very clean and sharp I found - no negative 'noise reduction' after effects that I could see.

I appreciate the OP was using extreme long exposures though....

The images would be dreadful Nigel. Dark Frame Subtraction is a very clever idea that works brilliantly, so I certainly wouldn't want to turn it off.

That seems to be the verdict after an interesting discussion calling it Noise Reduction is a bit confusing I feel. AFAIK there is no effective 'noise reduction' (as in a blurring type process, or colour noise reduction) applied in camera at all - the RAW file at most might carry an NR metadata value that could be read by Pentax Digital Camera Utility, but you'd have to be opening the files up in PDCU to see it applied by the software - I am not aware of any of these metadata values being applied by any other software.

I wonder, even for JPEG - is there actually any direct noise reduction process carried out on the saved files by the camera processor (like there is for sharpness, saturation, contrast etc) ??

Yes and no. DFS on its own works well but it's bad when it forces you to sit and wait for a camera to do its own internal thing like K7 does, it means the photographer can't take another pic during that time. It can't be turned off in K7 for exposures that are longer than 30s at all (cen be for 30s and shorter). It means take 30 minute pic, wait 20 minute, then be allowed to take another 30 min pic. Frustrating. This is why I had to buy a K5.

Fwiw, for trails the way round it is to use an intervalometer device and take lots of 30s exposures with DFS off and stack them. Works for trails cause you're faking it but that obviously won't get you single long exposure deep sky astronomy shots as they need to be one shot.