Calling 645Z owners - testing dark frame behaviour

**Ed Hurst** · 07-31-2014, 02:05 AM

Maybe it's the 10 degrees doing it

---------- Post added 07-31-14 at 07:06 PM ----------

After all, a cooler sensor will be less prone to noise all other things being equal

---------- Post added 07-31-14 at 07:08 PM ----------

Making it less in need to noise reduction. If that is the reason, it's quite an impressive little trick this beastie is doing. Wonder if it's measuring the ambient temperature and applying algorithms, or just measuring heat build up on the sensor. The latter makes more sense to be intuitively.

Either way, I wish we could have the choice of turning it off. Let us decide!

Royce Howland · 07-31-2014, 09:36 AM

Yeah, as mentioned there were no dark frames triggered from my 645Z either at ISO much higher than 3200. Given the pedigree of this sensor I'm surprised a 30s exposure would kick in dark frames at that low of an ISO setting, in 15C temps. It was a touch warmer than 15C when I tried a few night shots last week, and I got no dark frames all the way up to 51,200. Ed, just to confirm from earlier in the thread -- you have turned off the high ISO NR setting, right? I left the slow shutter speed NR setting at "auto", in the hopes that at least some of the time the camera would calculate that it didn't need to do NR.

jonojono · 07-31-2014, 09:42 AM

Originally posted by Ed Hurst

Maybe it's the 10 degrees doing it

---------- Post added 07-31-14 at 07:06 PM ----------

After all, a cooler sensor will be less prone to noise all other things being equal

---------- Post added 07-31-14 at 07:08 PM ----------

Making it less in need to noise reduction. If that is the reason, it's quite an impressive little trick this beastie is doing. Wonder if it's measuring the ambient temperature and applying algorithms, or just measuring heat build up on the sensor. The latter makes more sense to be intuitively.

Either way, I wish we could have the choice of turning it off. Let us decide!

Ed, I am going to try for the fun of it, ISO 3200 with a 2 minutes exposure at 27 degree C (in humid Singapore weather). Lets see what happens from there. Bc the initial photos I posted did not cause a dark frame.

Adam · 07-31-2014, 11:17 AM

Originally posted by 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

Originally posted by 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

As others have said, dark-frame-subtraction is either auto or on. When shooting some stars last night I noticed that at ISO 1600 and below, the camera wouldn't always apply DFS. Above 1600, however, I had to wait for it to do its thing. The temperature was around 40C, so not your typical weather.

The interface was a bit quirky- out of 6 5-minute shots, the countdown timer was only displayed 4 times. The other two times, I had to wait it out while the viewfinder/top LCD was frozen. I thought the camera froze completely, but eventually it wrote the file to the card and all was good

I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)

PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

robertchow999 · 07-31-2014, 02:29 PM

Originally posted by Adam

I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it.

Those pesky skeeters are the bane of my existence.

mikeSF · 07-31-2014, 05:28 PM

Originally posted by Adam

As others have said, dark-frame-subtraction is either auto or on. When shooting some stars last night I noticed that at ISO 1600 and below, the camera wouldn't always apply DFS. Above 1600, however, I had to wait for it to do its thing. The temperature was around 40C, so not your typical weather.

The interface was a bit quirky- out of 6 5-minute shots, the countdown timer was only displayed 4 times. The other two times, I had to wait it out while the viewfinder/top LCD was frozen. I thought the camera froze completely, but eventually it wrote the file to the card and all was good

I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it.

im laughing at that mosquito that got your TOE!
I remember waiting for a train to pass on a mosquito infested hillside. I covered my head, neck, ears, even had glasses to shield my eyes. Turns out, the fingerless gloves I wore allowed nearly every one of my fingers to get bitten by those relentless little suckers over a couple hours shooting...doh!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Calling all 31mm 1.8 limited owners!	1banger	Pentax SLR Lens Discussion	29	01-29-2015 07:38 AM
645Z and dark frame behaviour	Ed Hurst	Pentax Medium Format	3	05-14-2014 04:09 AM
Calling Tamron 10-24mm owners	ManixZero	Pentax SLR Lens Discussion	10	07-21-2009 12:48 PM
calling other FA31 owners	ilya80	Pentax SLR Lens Discussion	5	07-08-2009 12:43 PM
Calling all K200D Owners----please read	Ferdy	Pentax DSLR Discussion	13	01-20-2009 11:20 AM

07-31-2014, 02:05 AM	#46
Ed Hurst Site Supporter Join Date: May 2010 Location: Sydney Posts: 1,657 Original Poster	Maybe it's the 10 degrees doing it ---------- Post added 07-31-14 at 07:06 PM ---------- After all, a cooler sensor will be less prone to noise all other things being equal ---------- Post added 07-31-14 at 07:08 PM ---------- Making it less in need to noise reduction. If that is the reason, it's quite an impressive little trick this beastie is doing. Wonder if it's measuring the ambient temperature and applying algorithms, or just measuring heat build up on the sensor. The latter makes more sense to be intuitively. Either way, I wish we could have the choice of turning it off. Let us decide!

07-31-2014, 09:36 AM	#47
Royce Howland Senior Member Join Date: Nov 2010 Location: Calgary, Alberta Posts: 275	Yeah, as mentioned there were no dark frames triggered from my 645Z either at ISO much higher than 3200. Given the pedigree of this sensor I'm surprised a 30s exposure would kick in dark frames at that low of an ISO setting, in 15C temps. It was a touch warmer than 15C when I tried a few night shots last week, and I got no dark frames all the way up to 51,200. Ed, just to confirm from earlier in the thread -- you have turned off the high ISO NR setting, right? I left the slow shutter speed NR setting at "auto", in the hopes that at least some of the time the camera would calculate that it didn't need to do NR.

07-31-2014, 09:42 AM	#48
jonojono Forum Member Join Date: May 2014 Posts: 81	Originally posted by Ed Hurst Maybe it's the 10 degrees doing it ---------- Post added 07-31-14 at 07:06 PM ---------- After all, a cooler sensor will be less prone to noise all other things being equal ---------- Post added 07-31-14 at 07:08 PM ---------- Making it less in need to noise reduction. If that is the reason, it's quite an impressive little trick this beastie is doing. Wonder if it's measuring the ambient temperature and applying algorithms, or just measuring heat build up on the sensor. The latter makes more sense to be intuitively. Either way, I wish we could have the choice of turning it off. Let us decide! Ed, I am going to try for the fun of it, ISO 3200 with a 2 minutes exposure at 27 degree C (in humid Singapore weather). Lets see what happens from there. Bc the initial photos I posted did not cause a dark frame.

07-31-2014, 11:17 AM	#49
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Originally posted by 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 Originally posted by 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 As others have said, dark-frame-subtraction is either auto or on. When shooting some stars last night I noticed that at ISO 1600 and below, the camera wouldn't always apply DFS. Above 1600, however, I had to wait for it to do its thing. The temperature was around 40C, so not your typical weather. The interface was a bit quirky- out of 6 5-minute shots, the countdown timer was only displayed 4 times. The other two times, I had to wait it out while the viewfinder/top LCD was frozen. I thought the camera froze completely, but eventually it wrote the file to the card and all was good I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

07-31-2014, 02:29 PM	#50
robertchow999 Senior Member Join Date: Mar 2012 Posts: 117	Originally posted by Adam I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it. Those pesky skeeters are the bane of my existence.

07-31-2014, 05:28 PM	#51
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Originally posted by Adam As others have said, dark-frame-subtraction is either auto or on. When shooting some stars last night I noticed that at ISO 1600 and below, the camera wouldn't always apply DFS. Above 1600, however, I had to wait for it to do its thing. The temperature was around 40C, so not your typical weather. The interface was a bit quirky- out of 6 5-minute shots, the countdown timer was only displayed 4 times. The other two times, I had to wait it out while the viewfinder/top LCD was frozen. I thought the camera froze completely, but eventually it wrote the file to the card and all was good I wish I could have done more testing that night, but there were just too many mosquitoes! One ended up biting me in the toe and it hurt badly for almost an hour, so I had to call it. im laughing at that mosquito that got your TOE! I remember waiting for a train to pass on a mosquito infested hillside. I covered my head, neck, ears, even had glasses to shield my eyes. Turns out, the fingerless gloves I wore allowed nearly every one of my fingers to get bitten by those relentless little suckers over a couple hours shooting...doh!