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06-30-2014, 06:12 PM - 1 Like   #1
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Calling 645Z owners - testing dark frame behaviour

Hello all,

Congratulations to everyone on here who already has a 645Z - I am very jealous!

One thing that would be very interesting to me in weighing up the camera is its dark frame behaviour with long exposures (especially with multiple, consecutive long exposures). The 645D was odd in this respect - a custom function suggested the long exposure noise reduction could be turned off, but in practice, it would continue to shoot in some circumstances.

Does anyone who has a 645Z fancy testing this and sharing the results with the group please? I would be massively appreciative and I know I am not the only one interested in this. It is very relevant to shooting star trails pictures.

Essentially, the questions are:
1. Is the a custom function to turn off long exposure noise reduction?
2. If there is, please disable the long exposure noise reduction. If there is not, the following questions still apply.
3. If you shoot an exposure longer than 30 secs (say 45 secs, 1 minute and 2 minutes) does the camera shoot a dark frame immediately afterwards?
4. if you shoot a consecutive sequence of exposures of those lengths, does it shoot a dark frame after each of them, after only some of them or not at all?

It would be awesome to know!

Many thanks,

Ed

06-30-2014, 07:37 PM   #2
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QuoteOriginally posted by Ed Hurst Quote
Hello all,

Congratulations to everyone on here who already has a 645Z - I am very jealous!

One thing that would be very interesting to me in weighing up the camera is its dark frame behaviour with long exposures (especially with multiple, consecutive long exposures). The 645D was odd in this respect - a custom function suggested the long exposure noise reduction could be turned off, but in practice, it would continue to shoot in some circumstances.

Does anyone who has a 645Z fancy testing this and sharing the results with the group please? I would be massively appreciative and I know I am not the only one interested in this. It is very relevant to shooting star trails pictures.

Essentially, the questions are:
1. Is the a custom function to turn off long exposure noise reduction?
2. If there is, please disable the long exposure noise reduction. If there is not, the following questions still apply.
3. If you shoot an exposure longer than 30 secs (say 45 secs, 1 minute and 2 minutes) does the camera shoot a dark frame immediately afterwards?
4. if you shoot a consecutive sequence of exposures of those lengths, does it shoot a dark frame after each of them, after only some of them or not at all?

It would be awesome to know!

Many thanks,

Ed
Dear Ed, I will test for you wednesday and put up a full sized image through flickr. Will use the tripod and 25 F4.
07-01-2014, 01:13 AM   #3
Pentaxian




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Original Poster
Thank you so much! That's very kind of you. The behaviour of the 645D was interesting in this respect. Even with the long exposure noise reduction turned off, if behaved like this:
- Any exposure of longer than 30 secs would generate a dark frame after each shot;
- With exposures of shorter than 30 secs, there is no dark frame after the first frame, but if you shoot a sequence of consecutive frames (without gaps in between - either by locking the cable release shut or using the interval shooting mode on the camera), then it will shoot a dark frame after some shots but not others. This seems to be based on an algorithm looking at exposure length, number of shots taken and perhaps temperature. So it will unpredictably take a dark frame - which is very bad if you are shooting a sequence of shots to stack in star trail photography. I am hoping that the 645Z will not behave like this (i.e. that you can turn off the function in a way that actually does turn it off) or at least that there is a zone of exposure lengths that will reliably not lead to a dark frame (for example, that you can shoot limitless numbers of 45 sec exposures back to back without a dark frame, but if you shoot something longer, than it's a risk).

For you to establish this, it will take quite a lot of testing - shooting differing numbers of consecutive pictures with no gap between them, of differing lengths, and observing its behaviour. Do let me know if I can advise any further on the issue :-)

Many thanks again,

Ed
07-01-2014, 05:13 PM   #4
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thanks for asking, Ed. I too am very interested in being able to turn off the compulsory dark frame subtraction. I find it pretty much the only drawback of using my 645D. As a result, I have switched to my K5 for the star photos.

07-03-2014, 08:02 AM   #5
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Star trails are so yesterday With the clean high ISO of the Z, I suspect you can do some really sweet astrolandscaps where the goal is to freeze the the stars and get the landscape in one shot with a shutter speed just long enough. I tried it at ISO 3200 on 35mm format with good low light capability and the results were pretty good. I bet you could go ISO 6400 on the Z. Personally, I find the multiple exposures thing is more like data collection that photography to me.
07-03-2014, 08:27 AM   #6
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QuoteOriginally posted by tuco Quote
Star trails are so yesterday With the clean high ISO of the Z, I suspect you can do some really sweet astrolandscaps where the goal is to freeze the the stars and get the landscape in one shot with a shutter speed just long enough. I tried it at ISO 3200 on 35mm format with good low light capability and the results were pretty good. I bet you could go ISO 6400 on the Z. Personally, I find the multiple exposures thing is more like data collection that photography to me.
I'm with you on that last sentence.
07-03-2014, 09:03 AM   #7
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That is the $8,499 question - can this camera do real "pinpoint stars"/MilkyWay without using a tracker? The issue is that you will have to go much higher than ISO 6400 to get pinpoint stars or the exposure will be too long - there are no f2.8 wide angle lenses, nor any wide angle lenses for this system that are all that good wide open to begin with - so we'll have to stop down to probably f5.6 to get any real image quality out of those stars - which means a very long exposure and trailed stars, not pinpoint (unless you are just shooting to post on Facebook). So what does it look like at 12,800, or 25,600 in a nighttime scene? I'll be shooting the Milky Way tonight and will have my fingers crossed and just see what happens. I'll be using it with and without a tracker.
07-03-2014, 09:26 AM   #8
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...and still no answer to the question...

could someone with [access to] a 645Z please:
1) turn on camera. leave lenscap on
2) set to Bulb mode
3) press and hold down shutter for 35 seconds
4) observe what happens next

thanks!


Last edited by mikeSF; 07-03-2014 at 09:53 AM.
07-03-2014, 10:13 AM   #9
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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-MW-Ym7TnNUGh3a3BPeXdSZkk/edit?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.
07-03-2014, 10:15 AM   #10
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QuoteOriginally posted by jonojono Quote
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-MW-Ym7TnNUGh3a3BPeXdSZkk/edit?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.
and there it is. thanks for this info!
07-03-2014, 10:24 AM   #11
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QuoteOriginally posted by mikeSF Quote
...and still no answer to the question...

could someone with [access to] a 645Z please:
1) turn on camera. leave lenscap on
2) set to Bulb mode
3) press and hold down shutter for 35 seconds
4) observe what happens next

thanks!
Mike to answer this question. I did a one minute exposure specially for you all. Here is the link guys. https://drive.google.com/file/d/0B6-MW-Ym7TnNMDVfQXhhYjRTcjA/edit?usp=sharing

In short, after the exposure is done, the image is show for a brief period before you return back to the menu screen. Hope that helps.

And guys, all I ask is you support me in my site and write up and I am doing for this please. It is to help the community who were friendly enough to advice me

Last edited by jonojono; 07-03-2014 at 10:51 AM.
07-03-2014, 10:51 AM   #12
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QuoteOriginally posted by jonojono Quote
Mike to answer this question. I did a one minute exposure specially for you all.

In short, after the exposure is done, the image is show for a brief period before you return back to the menu screen. Hope that helps.

And guys, all I ask is you support me in my site and write up and I am doing for this please. It is to help the community who were friendly enough to advice me
yes, that means there is no one minute countdown for the dark frame exposure, so mystery is solved. thanks
07-03-2014, 10:54 AM   #13
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QuoteOriginally posted by mikeSF Quote
yes, that means there is no one minute countdown for the dark frame exposure, so mystery is solved. thanks
56 ISO 100, AWB, Landscape OOC JPEG, Auto LR, F8, MF, 30s
69 ISO 100, AWB, Landscape OOC JPEG, Auto LR, F8, MF, 1 minute.

Glad to report no dark frame substraction, NR can be switched for long exposure and you can continue after one long exposure shot. Photo preview will show and Menu will pop up .
07-03-2014, 10:57 AM   #14
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my only niggle with the 645D has been that an 8-minute night exposure takes a full 16 minutes before you can review the shot or shoot again.

Here's an 8-minute moonlight exposure:

see it on flickr: https://www.flickr.com/photos/mikeoria/13203307063/

It is a 2-exposure bracket, so it took over 24 minutes to capture with the 645D
07-03-2014, 11:15 AM   #15
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QuoteOriginally posted by mikeSF Quote
my only niggle with the 645D has been that an 8-minute night exposure takes a full 16 minutes before you can review the shot or shoot again.

Here's an 8-minute moonlight exposure:

see it on flickr: https://www.flickr.com/photos/mikeoria/13203307063/

It is a 2-exposure bracket, so it took over 24 minutes to capture with the 645D
great photos. followed you on flickr. do follow me as well.
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