645Z and dark frame behaviour

**Ed Hurst** · 04-26-2014, 11:34 PM

Hello all,

I have been watching the discussions on the 645Z with interest. One thing that will weigh heavily in my decision about whether to get one is the dark frame behaviour. On my 645D, although the firmware indicates the long exposure noise reduction can be switched off, in practice the camera continues to shoot dark frames when certain combinations of exposure length and temperature are met (which certainly precludes shooting sequences of exposures of the length required for one of my favourite subjects - star trails). As a result, I use my D800E for such images. If the new 645Z allows the dark frame behaviour actually to be turned off (which seems reasonable given the fact that the CMOS sensor will inherently handle long exposures better), then I may be tempted to buy one. Without this benefit, it is questionable...

Anyone know about how the 645Z operates in terms of its dark frame behaviour in practice?

All the best,

Ed

Bigvern1263 · 05-06-2014, 08:16 PM

Hi Ed, its my understanding that the CCD sensor in the 645D, needs this dark frame due to the heat that is generated by this style of sensor, the newer CMOS doesn't have these heat issues and hence you have a choice to turn on or off. I have to say i do a fair bit of LE BW with my 645D (5 MINS +) which is freaking painful as its then a 10 minute shot due to dark frame, but the noise and hot pixels etc are absolutely at a minimum. I have been considering the Sony A7R for this kind of work, due to the lower cost of camera, but its a del head spin with lenses, but it has the decent sized sensor for large prints, would love the Z but its a bit pricy right now and hard to justify…

**Ed Hurst** · 05-07-2014, 06:13 AM

Thanks Vern! Is that based on what would make sense logically (and I totally agree that it would) or knowing that the new Z actually behaves in this way (i.e. that the dark frame can be turned off in practice)?

Best wishes,

Ed

itshimitis · 05-14-2014, 04:09 AM

I was amazed at the lack of knowledge on this at high level within Pentax UK. And also with the European Service department which both assured me that the Dark frame could be turned off. I gave up. What I would say is that if you think it will be painless without dark frame, think again. I spent ages getting rid of hot pixels on the D800 on a 20 minute exposure. Mind you, with the D800/e you can turn the camera off after the exposure and the original shot will still be there. With the 645D no such luck, so to check exposure on a twilight/predawn shot is very painful.

04-26-2014, 11:34 PM	#1
Ed Hurst Site Supporter Join Date: May 2010 Location: Sydney Posts: 1,657	645Z and dark frame behaviour Hello all, I have been watching the discussions on the 645Z with interest. One thing that will weigh heavily in my decision about whether to get one is the dark frame behaviour. On my 645D, although the firmware indicates the long exposure noise reduction can be switched off, in practice the camera continues to shoot dark frames when certain combinations of exposure length and temperature are met (which certainly precludes shooting sequences of exposures of the length required for one of my favourite subjects - star trails). As a result, I use my D800E for such images. If the new 645Z allows the dark frame behaviour actually to be turned off (which seems reasonable given the fact that the CMOS sensor will inherently handle long exposures better), then I may be tempted to buy one. Without this benefit, it is questionable... Anyone know about how the 645Z operates in terms of its dark frame behaviour in practice? All the best, Ed

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05-06-2014, 08:16 PM	#2
Bigvern1263 Forum Member Join Date: Feb 2012 Location: QLD 4165 Photos: Albums Posts: 67	Hi Ed, its my understanding that the CCD sensor in the 645D, needs this dark frame due to the heat that is generated by this style of sensor, the newer CMOS doesn't have these heat issues and hence you have a choice to turn on or off. I have to say i do a fair bit of LE BW with my 645D (5 MINS +) which is freaking painful as its then a 10 minute shot due to dark frame, but the noise and hot pixels etc are absolutely at a minimum. I have been considering the Sony A7R for this kind of work, due to the lower cost of camera, but its a del head spin with lenses, but it has the decent sized sensor for large prints, would love the Z but its a bit pricy right now and hard to justify…

05-07-2014, 06:13 AM	#3
Ed Hurst Site Supporter Join Date: May 2010 Location: Sydney Posts: 1,657 Original Poster	Thanks Vern! Is that based on what would make sense logically (and I totally agree that it would) or knowing that the new Z actually behaves in this way (i.e. that the dark frame can be turned off in practice)? Best wishes, Ed

05-14-2014, 04:09 AM	#4
itshimitis Pentaxian Join Date: May 2011 Location: All over the place Posts: 3,535	I was amazed at the lack of knowledge on this at high level within Pentax UK. And also with the European Service department which both assured me that the Dark frame could be turned off. I gave up. What I would say is that if you think it will be painless without dark frame, think again. I spent ages getting rid of hot pixels on the D800 on a 20 minute exposure. Mind you, with the D800/e you can turn the camera off after the exposure and the original shot will still be there. With the 645D no such luck, so to check exposure on a twilight/predawn shot is very painful.