three shutter clicks heard with long exposure times on an M10-D

[fenykepesz]

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i expect to hear (and feel) two clicks with each picture taken with my M10-D - which is the case for all exposure times down to one second : a first strong click, and a second strong click.

THREE CLICKS issue : however when setting 2-8 seconds on the dial things sound strange :  for 8 seconds for example i hear a first strong click for opening the shutter curtain, then a second soft/faint click after 8s, and then a third strong click after another 8s (altogether approx 16sec) for closing the shutter curtain supposedly.  how do i explain these triplet of clicks and these two phases ('episodes') of picture taking ???  i never really payed attention to such slow exposure times, so i am not sure if this is a new 'feature'.  moreover i experience the same click behaviour at 2s and 4s, just proportionally shorter.  finally, which 8s 'episode' generates then my photo, the first or the second one ?

DARK BAND issue : now, pictures taken look alright - although the 8s landscape versions (iso=400) show today all a dark band at the top 10% of the photo : here an example (landscape width rescaled to 1K pixels) after i applied my usual b&w conversion protocol using gimp/gegl/c2g.  how do i explain that dark band at iso400/8s when at iso6400/1s no such artifact is visible, except for the expectedly increased picture noise ?

FW : 3.22.23.52

CORRECTION : this triple shutter click issue reported here i only seem to hear with the 8s exposure time - while 4s 2s 1s and shorter settings all sound as expected...

Edited December 27, 2023 by fenykepesz

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[AndreasG]

My M10-D does not show above symptoms at long exposure times, seems, there is something wrong with your camera. Note, the camera does not run the latest firmware, but one version back.

[robbie3]

My M10-D does the same thing as the original poster reports.

If I take an 8 sec exposure with the lens removed at 8 seconds I see an all black shutter close, then at 16 secs the main shutter curtain closes.

I believe this is to enable the dark frame that's taken for long exposure noise reduction (LENR) processing for exposures of 8 secs and longer.

Edited December 27, 2023 by robbie3

[fenykepesz]

this triple click thingy is getting more interesting, and thank your @robbie3 for pointing me in the right direction !  me too thought about looking onto the shutter itself but it was a bit late last night and then i hate to take off the camera lens in my dusty apartment.

in any case, i can confirm your observation : at 8s exposure AS WELL AS with the B aperture mode there is this dark curtain closing first, the middle click, while the third click comes with the closing of the usual black-gray-white curtain.  the only difference is that in B-mode the two symmetrically-spaced time phases between the three clicks are as long as set (anything from very short to many seconds or longer) while for the preset fix 8s exposure both these two phases are equally 8s long.

now, does this mean that the camera is unresponsive during that 2nd shutter closing phase for further camera actions, i.e. taking a new next photo ?  that may not be very practical for very long B-shots because then the camera would be 'bizi' (unresponsive) for double the length of the chosen exposure time...?  i guess it makes sense to delay a bit that 2nd curtain closure to avoid the associated vibrations - just why do so after such a long waiting time, instead of a default one-second delay for example ?

i will as suggested by @AndreasG try at some point that newest firmware i wasn't aware of - perhaps that will fix this triple-click 'feature' !

[fenykepesz]

to @robbie3 : what is this "long exposure noise reduction (LENR)" ?  a special digital process ?  which may be the culprit for that dark band artifact i described initially ?  it's visible already in the color RAW DNG file and hence unrelated to my c2g processing pipeline, correct ?

[fenykepesz]

oops - i just saw that others in the past had dealt with the same 'triple-click' and LENR issues...

[jimofnyc]

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once the initial exposure is complete the shutter closes again for the same amount of time needed for the actual exposure.  A "blank" black image is created with all the pixels that may have gone awry ~ being anything but black.  This image is subtracted from your actual image exposure to remove any glitches of the sensor created during long exposure time.

 

[fenykepesz]

wow, thank you, @jimofnyc - very informative, learned a lot !  that means one is luckily immune to camera movements or changes in the scenery during the 2nd exposure phase, while the blank black image is recorded and the camera itself is locked.

in any case, this dual exposure routine as sophisticated as it sounds is unfortunately in principle unable to clean out those dust devils from my picture taken if you look at my link above that reveals quite a few distinct soft dark spots on the white bathroom tiles... while the situation here a year earlier turned out a bit 'cleaner'...

[AndreasG]

vor 22 Stunden schrieb AndreasG:

My M10-D does not show above symptoms at long exposure times, seems, there is something wrong with your camera. Note, the camera does not run the latest firmware, but one version back.

I need to correct my above statement: My camera also shows the "double" exposure, but only if a lens is mounted. Without lens, only one exposure as I stated in #2.

[adan]

Just for clarification, the LENR (long exposure noise reduction) detects pixels that produce current or charge from other sources than the light/photons coming through the lens.

It can be a "stuck pixel" that is always producing a signal, regardless of whether electromagnetic radiation (EMR) is hitting it.

Or it can be EMR "noise" in the near-visible parts of the EMR spectrum (e.g. infrared photons for nearby warm camera electronics)

Or it can even be "radiowave" radiation emissions from camera parts (running wifi?) - or even just the cosmos (random cosmic-ray particles that are sleeting down on us all the time).

The second "dark" exposure will register such "non-image" pixel output as inappropriate bright spots/pixels, which can be used to mask out those same spots in the original image before sending it on to the SD card.

Always remember that image sensors are "quantum devices" (as are most silicon chips) - they are subject to the Heisenberg Uncertainty Principle. The more precisely we try to measure the position of a photon (it hit THIS exact pixel), the less certain we can be of its energy.

But an error-checking system (in this case the dark exposure) can rein in the uncertainty - something that appears in both the dark exposure and in the intended picture is likely an artifact of the device, not a representation of reality.

It is not perfect - the image of a bright star may very well have fallen on a pixel that is also "stuck," and be mistakenly erased. But the odds (Bog DOES play dice with the Universe!) are that it is an artifact.