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Long exposure NR

Discussion in 'X-Pro2 and X-Pro1' started by markopa, Apr 13, 2012.

  1. markopa

    markopa Premium Member

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    Hi,

    Recently I've been doing some long exposure (>5s) with the xpro1. I've enabled the "Long exposure NR" option in the menu. AS I understand (from my Nikon) with this option ON the camera should take two images. The first one exposing to the scene and the second on with the shutter closed. Basically the second image measures the noise generated (same exposure length) on a pure black scene. Later the in-camera firmware subtracts the two images and you get a perfectly clean image.

    However the "quirky gem" is taking just one exposure with this option turned on.

    Does anybody know how "long exposure NR" works in xpro1 ?

    Marko
     
  2. Arjay

    Arjay Admin Staff Member

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    Your general description is correct.

    But how do you know the camera isn't taking a second exposure? The second exposure does not require a mechanical shutter cycle. The only indicator that "Long exposure NR" is occurring is the fact that the camera will roughly take twice the measured exposure time before you can view the image the camera has taken.
     
  3. markopa

    markopa Premium Member

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    I know that is not taking the second exposure as when the first exposure ends I can review the image immediately. If it would take two exposures the whole procedure would take 2x (+post processing) the time of the exposure time.
     
  4. Arjay

    Arjay Admin Staff Member

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    Hm, that's interesting. Maybe somebody else can do a little long-exposure test with his X-Pro1 to verify. I'll probably be able to verify this next week, when I'll have the camera in my hands.
     
  5. rift_zone

    rift_zone Member

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    I've done several long exposures with Long Exposure NR on my X-Pro1 and it certainly does take 2 exposures. I took a 15 minute exposure and it took 15 minutes after the first exposure before I could take another shot. I've just taken another test shot to verify this, this time a 1 minute exposure with a resulting 1 minute second exposure. All seems to be working as intended on my camera.
     
  6. markopa

    markopa Premium Member

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    Ok, I've just redo another test.

    With the camera set to 'T' mode, M focus mode, exposure of 15s and Long exposure set to ON I the LCD becomes active (I can see the scene) just after 15 seconds, which tells me the camera isn't taking two exposures.

    @rift_zone: how do you know is taking 2 exposures ? What are your camera settings ?

    It would be great if somebody else could confirm.
     
  7. rift_zone

    rift_zone Member

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    From the tests I have done it looks like the noise reduction doesn't kick in until exposures are longer than 1 minute 15 seconds. Try setting your camera to bulb and holding the shutter for 1 minute 16 seconds and see if the camera "processes" the picture for the same amount of time. The fact that the camera processes the picture for the exact same time as the shutter has been depressed (after 1 minute 15 anyway) tells me it's taking a second exposure.
     
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  8. Bigkidneys

    Bigkidneys New Member

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    Yep, I noticed it happening after 1 minute plus exposures. Same happened to me with my K5. Anything less than a minute or so was literally available immediately. Anything over and it started a countdown.
     
  9. markopa

    markopa Premium Member

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    Ok. That's maybe explains it. I was used to my D700 which applies NR (2nd shot) after you go beyond 2 seconds.
     
  10. Quitsa

    Quitsa New Member

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    I just tried it on my X Pro 1 and it appears there are some nuances to how it works. With a 30 second "B" exposure and aperture ring set to "A", after the shutter closed, the display said "Processing" for another 30 seconds and the camera would not allow any operations. The same is true of a 30 second exposure at "T" with the aperture rind manually set to f/1.4. However, a 30 second exposure under B mode with a manual aperture setting does not seem to trigger the noise reduction processing.
     
  11. Mr SMW

    Mr SMW Triple Platinum Member

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    Have you tried any comparable long exposures with in camera NR to off at all...and if so, how do they compare?

    Pain in the neck waiting 30 mins for what was a 15 min exposure...if the difference can be corrected in post?

    But then I am a novice when it comes to long exposure and waiting on an ND10 :)
     
  12. rift_zone

    rift_zone Member

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    I've tried a few comparable exposures with Long Exposure NR set to off, up to about 5 minutes, and the photo is almost immediately processed, no long waits. However image quality is noticeably poorer. No doubt it is a hassle having to wait double the time of the exposure, but the results make it worthwhile. I quite often take a couple of beers with me when I'm doing long exposures, it helps pass the time. :)
     
  13. cbwerner

    cbwerner New Member

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    If the delay when shooting is troublesome, this is easy to do in post processing. It's called dark reduction, and we do it all the time in astrophotography. You basically take and keep exposures of differing durations with the lens cap on to create a library of dark frames at various exposure lengths to apply in Photoshop or whatever. There may even be some plugins that will batch process the exposures if you have a bunch.

    Edit: I forgot to make it clear that you a series of exposures for each ISO/gain setting that you are going to use, so 2 mins @ 1600, 2 mins @3200, etc..
     
  14. jlaronge

    jlaronge Premium Member

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    There's a good explanation of how to do this in post here: http://photo.net/learn/dark_noise/
     
  15. rift_zone

    rift_zone Member

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    That sounds very interesting. But it would mean I would have less time for drinking beer. :p I'll check it out. Thanks.
     
  16. rift_zone

    rift_zone Member

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    I'll look into that. Thanks.
     
  17. markopa

    markopa Premium Member

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    Ok, it would be ok if we end up with a procedure to explain to the support so they can fix this issue. NR should be applied to any photo regardless of the mode setting if 'Long exposure NR' is turned on. At least I've paid 2500€ for this, damn !
     
  18. jlaronge

    jlaronge Premium Member

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    I don't think there's an issue. I just ran a test. I did a 28min 50 sec. exposure @ ISO 200 with long exposure NR ON. I did this using the lcd screen. When the exposure finished, on the top left of the screen a message "M processing..." appeared and no other functions on the camera were possible. This lasted for ~28min. 50 sec.. I repeated this with 90 sec., and 5 min. exposures with the same results.
     
  19. markopa

    markopa Premium Member

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    AS reported above, it seems this is very dependent of the aperture setting and on the B and T setting.
     
  20. jlaronge

    jlaronge Premium Member

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    I just did a test reproducing what was above, here's the results:

    All @ISO 200, Manual focus, Long Exposure NR On

    T @30sec. f1.4 - ready to shoot right away

    T @ 30sec. Aperture set to A - ready to shoot right away (camera chose f1.4)

    B @ 30sec. f1.4 - ready to shoot right away

    If you put the camera on B and set the Aperture ring to A, you get a 30sec. f1.4 exposure. It functions like it's in T mode.

    I also tried B for 30sec., 45sec., 1min. all @ f16 ISO 200 and all were ready to shoot right away. At 1min.15sec. the M Processing message comes up.

    In T or B at ISO 6400 f16 the M Processing message comes up at 2sec. and longer.
     
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