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Re: [OM] Oddball solution to reduce long exposure noise

Subject: Re: [OM] Oddball solution to reduce long exposure noise
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 17 Dec 2017 00:49:37 -0800
On 12/14/2017 4:46 PM, Mike Gordon via olympus wrote:
...Wayne writes:

<<Do you think something like a heavy block of metal screwed to the camera via
<<the tripod thread would work to keep the electronics cool ?  You could
<<always keep it in the fridge for a while prior to use.


The battery business adding to noise is hearsay, but from a good source.

Michael Covington, in Digital SLR Astrophotography?

"Cool-down between long exposures -
Like all electronic devices, the sensor in your camera emits some heat while 
it’s
being used. As the sensor warms up, its noise level increases, leading to more
speckles in your pictures. This effect is usually slight and, in my experience,
often unnoticeable; it is counteracted by the fact that the temperature of the 
air
is usually falling as the night wears on.
Nonetheless, for maximum quality in images of faint objects, it may be 
beneficial
to let the sensor cool down for 30 to 60 seconds, or possibly even longer,
between long exposures"

"Effect of temperature -
Leakage, or dark current, is affected by temperature; that’s why astronomical
CCD cameras have thermoelectric coolers. Even DSLRs are noticeably less noisy
in the winter than in the summer; that’s why dark frames should always be taken
at the same temperature as the images from which they will be subtracted.
Theoretically, the dark current of a silicon CCD sensor doubles for every 8◦ C
(15◦ F) rise in temperature.3 This relationship is affected by the way the 
sensor
is fabricated, and I have not investigated whether it is accurate for the 
latest DSLR sensors.
What is definite is that there’s less noise in the winter than in the summer.
At this point you may be thinking of chilling the camera. This has been tried,
but one obvious drawback is that moisture from the atmosphere will condense
on the sensor if the sensor is cold enough"

There should be a more elegant engineering solution but that does
not appear to be  Sonnie's style.  The A7R sensor is intrinsically much less 
noisy --something to do with BSI structure on later models perhaps. One would 
have though thermoelectric cooling  (Peltier) for that scenario could have been 
added, or some other cooling feature.

Battery problem.

They did not even bother to add lossless compressed raw
or fix the star eater issue which should have been a piece of cake and a few 
lines of code in the firmware.   The weather sealing on a teardown of the OM  
A7RIII is at least there, but not very robust.
IMO, still by far the best digital back for Zuikos for many purposes.  It is a 
dust magnet too  and now spoiled  by E-M1 Mk11 which is just the opposite.

Yes, enough time with Oly 4/3 and µ4/3 makes going back a shock. Panny must have something similar, as I've had almost no trouble with GX7, GM1 and GM5. There is a short delay when turning off . . .

Les D. Moose

--
What if the Hokey Pokey *IS* what it's all about?
--
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