[jwoodland]

The 645z that I have only has options for Long Exposure Noise Reduction (Slow Shutter Speed NR) AUTO or ON - could someone tell me where to find the OFF setting? (I must be blind, but page R17 is all I see and I can't find it in the menu.) As Jono noted in his post - "1) Yes NR can be switched off manually." Thanks.

jonojono
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Join Date: May 2014
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Dear all. To answer your question in short.

1) Yes NR can be switched off manually.
2) I did a 30 seconds multiple times with internal shooting. No problem. See attached photo and download from google. Settings were ISO 100, F8, 30s exposure, auto correction on LR (https://drive.google.com/file/d/0B6-...it?usp=sharing)

---------- Post added 07-04-14 at 01:14 AM ----------

Did longer than 90s. No problem mate. I can continue as though life is normal.


Read more at: https://www.pentaxforums.com/forums/48-pentax-645d-medium-format/266933-calli...#ixzz38iqT1n79

[jonojono]

The 645z that I have only has options for Long Exposure Noise Reduction (Slow Shutter Speed NR) AUTO or ON - could someone tell me where to find the OFF setting? (I must be blind, but page R17 is all I see and I can't find it in the menu.) As Jono noted in his post - "1) Yes NR can be switched off manually." Thanks.

jonojono
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Join Date: May 2014
Posts: 71 | Likes: 4
Dear all. To answer your question in short.

1) Yes NR can be switched off manually.
2) I did a 30 seconds multiple times with internal shooting. No problem. See attached photo and download from google. Settings were ISO 100, F8, 30s exposure, auto correction on LR (https://drive.google.com/file/d/0B6-...it?usp=sharing)

---------- Post added 07-04-14 at 01:14 AM ----------

Did longer than 90s. No problem mate. I can continue as though life is normal.


Read more at: https://www.pentaxforums.com/forums/48-pentax-645d-medium-format/266933-calli...#ixzz38iqT1n79

Should have been more specific. You can choose to select NR at certain ISO to be off. So I do mine from base ISO to 3200. I haven't had the issue where I have to wait. However, that said, sometimes when I shoot at 6400 or greater, the NR kicks in and you have to wait. Set it to AUTO and in the manual selection for NR reduction at various ISO, do your adjustments from there. Hope it helps. For long exposure, 100-1600 I don't have dark frame subtraction. My 30 min one seemed ok at base 100 and at ISO 200.

[itshimitis]

My experience that the settings are On or Auto. I couldn't find an off switch for it. There doesn't seem to be a particular time limit for where it comes in, the camera seems to evaluate the scene to say yes or no

[jwoodland]

OK thanks, that clears it up - the processor measures the sensor and takes exposure time and ambient temp into consideration and then decides to do a dark slide or not. That is the same way the 645d worked - sometimes it did one at a particular exposure time, sometimes it did not. The Z seems to have much more latitude and therefore longer times/higher temp before it kicks in, but still no way to actually turn it off as had been reported. When shooting a 1,000-frame time-lapse of 30 second images in the summertime I suspect it would kick in all the time, so doing a time-lapse would not be possible without the potential of having the dark frame kick in.

So the correct answer is there is no way to actually turn the dark frame off for sure - it just all depends on what the camera thinks should be done. Bummer.

[Ed Hurst]

It seems to me that two different issues are becoming confused here, leading to the advice being (no doubt unintentionally) erroneous. The camera has two noise reduction functions - one for high ISO and one for long exposures. They are independent of each other. My question (and I believe the interest shown by others here) relates to the latter. The advice that noise reduction can simply be turned off seems to relate to the former. It's unfortunate that this misunderstanding took place as it has very important implications for anyone wishing to shoot star trails and the like with the camera - which requires long exposure noise reduction to be reliably and consistently turned off. I fear the advice may have led purchasing decisions down the wrong path.

That said, all may not be lost. Since the 645Z does seem to be more forgiving - and does not fire a dark frame as readily - it may be that there is a zone of exposure lengths / temperatures in which a dark frame will not be fired at all (even after a large number of consecutive frames has been fired) - including situations in which the 645D does fire a dark frame; knowing what that zone is would be most useful! But it remains a pity that we cannot simply turn the function off - and that the above confusion seems to have taken place.

[mikeSF]

wait, are you saying that when it was answered earlier in this thread that the 645Z has the ability to turn off the dark frame subtraction for exposures longer than 30sec, that information was UNTRUE?

presently, with the 645D, all exposures longer than 30sec are immediately followed by a dark frame exposure of same duration, which is not selectable.
The K-cameras allow this to be turned off.

ok, what is the true answer?
thanks

[itshimitis]

wait, are you saying that when it was answered earlier in this thread that the 645Z has the ability to turn off the dark frame subtraction for exposures longer than 30sec, that information was UNTRUE?

presently, with the 645D, all exposures longer than 30sec are immediately followed by a dark frame exposure of same duration, which is not selectable.
The K-cameras allow this to be turned off.

ok, what is the true answer?
thanks

It is two settings - Auto or On.

There isn't a set time limit. I did about 7 sets of 2 minute+ exposures. On a 3min 30 it didn't do it, but on the following 2 min 30 it did.

[jonojono]

wait, are you saying that when it was answered earlier in this thread that the 645Z has the ability to turn off the dark frame subtraction for exposures longer than 30sec, that information was UNTRUE?

presently, with the 645D, all exposures longer than 30sec are immediately followed by a dark frame exposure of same duration, which is not selectable.
The K-cameras allow this to be turned off.

ok, what is the true answer?
thanks

To answer, like what itshimitis , it is dependant on your scene or luck. I haven't had it do dark frame subtraction until high ISOs. I apologise for the confusion initially.

---------- Post added 07-29-14 at 04:42 PM ----------

It seems to me that two different issues are becoming confused here, leading to the advice being (no doubt unintentionally) erroneous. The camera has two noise reduction functions - one for high ISO and one for long exposures. They are independent of each other. My question (and I believe the interest shown by others here) relates to the latter. The advice that noise reduction can simply be turned off seems to relate to the former. It's unfortunate that this misunderstanding took place as it has very important implications for anyone wishing to shoot star trails and the like with the camera - which requires long exposure noise reduction to be reliably and consistently turned off. I fear the advice may have led purchasing decisions down the wrong path.

That said, all may not be lost. Since the 645Z does seem to be more forgiving - and does not fire a dark frame as readily - it may be that there is a zone of exposure lengths / temperatures in which a dark frame will not be fired at all (even after a large number of consecutive frames has been fired) - including situations in which the 645D does fire a dark frame; knowing what that zone is would be most useful! But it remains a pity that we cannot simply turn the function off - and that the above confusion seems to have taken place.

Initially what was asked was a comparison for 30s or greater. I did 30s and 1 minute.

Ed, I know it is two different things. But I experimented and realised had this observation. When I did long exposures at low ISOs, there didn't seem to be that dark frame subtraction. I have gone up to about 10 minutes at ISO 100 with nothing at all. However, when I tried that at higher ISOs, it would do with a long exposure.

Left it at ON and went back to the other function and played around with it. The one for high ISO and set those to off (from 100-3200). And at higher isos (even up to 1600), it did not appear to compensate with a dark frame. So I guess there must be some algorithm with the scene where the 645Z decide to fire a dark frame, maybe the ISO sensitivity plays a part as well.

Again, this dark frame firing could happen after a sequence of 2-3 long exposures where the camera needs to "cool down".

[jwoodland]

I shot about 100 frames of the Milky Way early this morning with the Z on AUTO and it did a dark-frame for EVERY shot (and then after the dark frame it took another 8-10 seconds for the file to be written and camera controls available again). These were all high ISO (I guess that term is relative, but to me it begins at 6400), from 6400 to 25600. The temp was cool, in the 60's, with most exposure times being 10 seconds up to 120 seconds (some of those on a tracker). There is no OFF on this camera, so it is just like the D in that regard, and when shooting high ISO it kicks in most of the time (at least beginning at 10 seconds), so no time-lapse of the Milky Way possible it looks like. So it is a combination of High ISO, exposure time, and air/sensor temp, but most of the time at High ISO it will be on, which is a big disappointment for star shooters like me - still INCREDIBLE for a medium-format camera, just disappointing.

[jonojono]

I shot about 100 frames of the Milky Way early this morning with the Z on AUTO and it did a dark-frame for EVERY shot (and then after the dark frame it took another 8-10 seconds for the file to be written and camera controls available again). These were all high ISO (I guess that term is relative, but to me it begins at 6400), from 6400 to 25600. The temp was cool, in the 60's, with most exposure times being 10 seconds up to 120 seconds (some of those on a tracker). There is no OFF on this camera, so it is just like the D in that regard, and when shooting high ISO it kicks in most of the time (at least beginning at 10 seconds), so no time-lapse of the Milky Way possible it looks like. So it is a combination of High ISO, exposure time, and air/sensor temp, but most of the time at High ISO it will be on, which is a big disappointment for star shooters like me - still INCREDIBLE for a medium-format camera, just disappointing.

jwoowland. try to go 3200 with a 30s exposure on F4/F5.6. Do the settings adjustment in the one for high ISO and set those to off (from 100-6400). Weirdly mind didn't do a dark frame until I hit 12800. 6400 was a bit of a hit and miss. Mine doesn't kick it for 6400 at 30s at times. And my temperature was relatively cool (10-18 degrees C). So it might be a combination before dark frame kicks in.

[jwoodland]

Yes, mine kicked in at ISO 3200 during long exposures last night. I think the only real question was could this be turned off, and obviously it cannot, so same as the 645d. Oh well. Those high ISO files sure are nice!

[Ed Hurst]

One question is how it behaves with single frames at various ISOs. The other is how it behaves with a series of consecutive frames. I will try to do some testing.

[Royce Howland]

I did a small amount of night shooting last week with the 645Z. (Less than I was hoping to do because conditions were not ideal and I was too tired to stay up for it under the circumstances. ) Going up to ISO 51,200 and exposures up to 30 seconds, I did not get any dark frames happening. I have high ISO NR set to "off", and slow shutter speed NR set to "auto" (since the latter can't be turned off). I was just shooting single frames, not trying to do any interval shooting over a longer run; and also not trying any bulb exposures longer than 30s.

The 645Z seems to have a wider range of exposures that can be shot without dark frames coming into play, compared to the 645D. But as with the D, it seems like it can't actually be disabled completely on the Z.

[Ed Hurst]

No formal testing per se yet. But shooting at ISO 1250 with 15 sec exposures at around 15 Celsius appears to allow shooting without dark frames (if that function is set to 'auto'). On the other hand, exposures at ISO 3200 seem unavoidably to trigger a dark frame. So there is support for the idea that it cannot be turned off, but it is more forgiving than the 645D in when it decides to trigger. More structured testing to follow...

[jonojono]

No formal testing per se yet. But shooting at ISO 1250 with 15 sec exposures at around 15 Celsius appears to allow shooting without dark frames (if that function is set to 'auto'). On the other hand, exposures at ISO 3200 seem unavoidably to trigger a dark frame. So there is support for the idea that it cannot be turned off, but it is more forgiving than the 645D in when it decides to trigger. More structured testing to follow...

As weird as it seems, mine doesn't trigger at 3200 at 30s at around 10 degrees C. So I am not sure why...