Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-01-2012, 07:41 AM   #16
Veteran Member
Ryan Tischer's Avatar

Join Date: Feb 2012
Location: Duluth, Minnesota
Photos: Albums
Posts: 434
Original Poster
QuoteOriginally posted by alunfoto Quote
I experimented with really long exposures this winter, and found that the 645D sensor is sensitive to what the astronomers call "spurious noise".
Thank you for those interesting tidbits. I'm assuming they are a minor pain and pretty easy to clone out, much like sensor dust in most cases. Before I print, I always zoom into 100% and scan the image for any problematic dust, etc. and do a little cloning.

05-01-2012, 07:48 AM   #17
Veteran Member




Join Date: Feb 2011
Photos: Gallery
Posts: 573
QuoteOriginally posted by jwoodland Quote
<<That is your dark-noise frame which you can subtract from your actual exposure and can be done in post processing.>>

How do you actually subtract the dark frame in Photoshop? Thanks....
In Photoshop, you can subtract images in the layers palette. Simply set the layer to be subtracted from the image below it. There is a drop-down menu to set that in the palette.
05-01-2012, 08:07 AM   #18
Forum Member




Join Date: Dec 2011
Posts: 90
Got it - thanks! I never noticed "subtract" on the list before!
05-02-2012, 08:46 AM   #19
Forum Member




Join Date: Apr 2008
Location: Norway
Photos: Gallery
Posts: 72
QuoteOriginally posted by Ryan Tischer Quote
Thank you for those interesting tidbits. I'm assuming they are a minor pain and pretty easy to clone out, much like sensor dust in most cases. Before I print, I always zoom into 100% and scan the image for any problematic dust, etc. and do a little cloning.
The effect is cumulative, and In my experience it got annoying with exposures at 8 minutes and longer. But I suppose the amount of spurious noise accumulated will depend on many things. At my latitude there are sometimes auroras. It seemed to me that the spurious noise became more abundant then, but it may have been a coincidence.

Hope for your sake that you continue to be un-annoyed. Apart from the spurious noise, the image quality is certainly soothing.

05-03-2012, 11:36 PM   #20
Forum Member




Join Date: Feb 2012
Location: QLD 4165
Photos: Albums
Posts: 67
Hi guys, can someone confirm the NR system on 645D, i have downloaded latest FW from site and updated camera.

The NR still takes another DARK exposure, i CANNOT turn it off, ie take one exposure at 60 secs,(BULB MODE) it auto takes another(Dark) when first one is taken fro same or similar time. !!
I have tried changing the NR settings in the menu but to no avail.. no matter wether switched on or off it does the same thing..

Any help or feedback is much appreciated.

Cheers.
PS i thought i had read somewhere becuase of sensor type and the heat it generates it was not possible to turn tis feature off , but then why have the option. ??
05-05-2012, 09:38 AM   #21
Forum Member




Join Date: Apr 2008
Location: Norway
Photos: Gallery
Posts: 72
QuoteOriginally posted by Bigvern1263 Quote
Hi guys, can someone confirm the NR system on 645D, i have downloaded latest FW from site and updated camera.

The NR still takes another DARK exposure, i CANNOT turn it off, ie take one exposure at 60 secs,(BULB MODE) it auto takes another(Dark) when first one is taken fro same or similar time. !!
I have tried changing the NR settings in the menu but to no avail.. no matter wether switched on or off it does the same thing..
I can confirm that my camera does the same thing. In "B" mode, the camera will do a dark-frame after every shot no matter what.

I think the workaround is to take multiple 30-second shots and stack them in the computer afterwards, using astrophoto software. Some plugins for Lightroom or Photoshop may also do the job, I think.

I have tried to use multi-exposure too, but the camera is not as good as computer software at separating true detail from noise.
05-06-2012, 10:42 PM   #22
Forum Member




Join Date: Feb 2012
Location: QLD 4165
Photos: Albums
Posts: 67
Many thanks Alunfoto, i would be interested to hear what any others have to say on this matter? re the B mode and Dark exposures on anything over 30 secs . Ie NR cannot be turned off ..

Cheers Guys.
05-09-2012, 07:15 PM   #23
Forum Member




Join Date: Feb 2012
Location: QLD 4165
Photos: Albums
Posts: 67
Hi, in regards to post above, have any other 645D users switched there camera to BULB mode and taken an exposure over 30 secs ??? if so does it take another DARK exposure for NR purposes ? can you turn off NR ?? Or i will rephrase that, SW says you can turn it off, but does it actually turn off ? i have latest FW and my 645D continues to take a NR exposure regardless of settings....

Cheers.

05-11-2012, 07:22 AM   #24
Junior Member




Join Date: Jan 2011
Location: United States
Posts: 36
I was doing some 4-8 min exposures the other night using B. I can confirm the camera does take a similar length dark exposure immediately after. I haven't tried turning it off though, so I'm not sure long exposure noise reduction is on or off. I'll take a look when I get home tonight.

Jeff
05-11-2012, 07:05 PM   #25
Pentaxian




Join Date: May 2011
Location: All over the place
Posts: 2,467
I have posted about this before and have spoken to pentax europe about it. Pentax Europe had no clue about it whatsoever. I won't be calling them for advice in future! I'm still waiting for my 645D to be repaired but it was up to date and the NR frame happened regardless of what I had set in settings
05-11-2012, 10:19 PM   #26
New Member




Join Date: Sep 2010
Location: Pebble Beach, CA
Posts: 12
Why does your 645D need repair?
05-12-2012, 01:11 AM   #27
Pentaxian




Join Date: May 2011
Location: All over the place
Posts: 2,467
There is a whole thread on it! Impact damage so expensive repair although not a major repair
05-12-2012, 05:11 AM   #28
Junior Member




Join Date: Jan 2011
Location: United States
Posts: 36
QuoteOriginally posted by Bigvern1263 Quote
Hi, in regards to post above, have any other 645D users switched there camera to BULB mode and taken an exposure over 30 secs ??? if so does it take another DARK exposure for NR purposes ? can you turn off NR ?? Or i will rephrase that, SW says you can turn it off, but does it actually turn off ? i have latest FW and my 645D continues to take a NR exposure regardless of settings....

Cheers.
I tested my camera. Slow shutter speed noise reduction only effects exposures <= 30 sec. If you take an exposure over 30 sec (using B) it will do a dark frame regardless of the setting.
05-12-2012, 09:00 AM   #29
Forum Member




Join Date: Apr 2008
Location: Norway
Photos: Gallery
Posts: 72
QuoteOriginally posted by jwjohnson Quote
I tested my camera. Slow shutter speed noise reduction only effects exposures <= 30 sec. If you take an exposure over 30 sec (using B) it will do a dark frame regardless of the setting.
One more; Thanks jwjohnson.

Dunno what it is about his own camera that Bigvern doesn't trust...
05-12-2012, 11:30 PM   #30
Forum Member




Join Date: Feb 2012
Location: QLD 4165
Photos: Albums
Posts: 67
Thanks guys, i was curious thats all, as i do a few LE seascapes etc, which can run into minutes, and all the while the sky etc is changing, so the extra dark frame is more a pain than anyhting.
If it cant be turned off why have it in the software suggesting you can ?
And also in this earlier thread some posters had suggested it didnt do a dark exposure ??

Thanks itshimitis, can you point me to the thread you started on this? cheers.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
645d, camera, exposures, medium format, nr, results, shutter
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Slow shutter speed comovartia Troubleshooting and Beginner Help 7 07-29-2011 02:45 PM
Winners - P-52 Week 49 Shutter Speed -Slow casil403 Weekly Photo Challenges 8 07-13-2011 03:11 PM
Pentax KX Shutter starting to stuck at slow shutter speed. Spirit722 Pentax Film SLR Discussion 7 03-03-2011 09:49 PM
Rear curtain and slow shutter speed flash sync question for the 645D Warped Pentax Medium Format 9 01-28-2011 11:36 AM
67 shutter lock for long exposures? Mike Pentax Medium Format 15 12-09-2010 05:45 PM



All times are GMT -7. The time now is 03:14 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top