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Canon SX40HS long expoisure noise problems

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Offline Recyclojunk64

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Re: Canon SX40HS long expoisure noise problems
« Reply #10 on: 14 / May / 2013, 11:31:38 »
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Here are some samples at lower ISOs.

The exposure time was increased proportionally with the lowered iso. For some reason the 2048second overide did not seem to work so I had to use 1625s.



I was planning on taking this one at 2 hours (1hour, 59minutes, 59s, with the new long exposure feature in the development trunk) but the camera crashed with an error code "e26" (guess I will save that problem for another thread though). No noticeable noise though, as expected.



Just the above with the brightness increased 5x to simulate a 2 hour exposure (although I'm sure there would be less noise though in it since it would average out somewhat)




A close up of the noise in my last post. What I don't understand is why there are those horizontal streaks with neatly-spaced dots though. It's exactly the same in the raw image as well. Any idea why it is showing up like that and not like conventional random  noise per individual pixel?
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Offline outslider

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Re: Canon SX40HS long expoisure noise problems
« Reply #11 on: 14 / May / 2013, 13:06:20 »
I'm not sure about the noise but it seems as something related to the sensor itself and I wouldn't expect that covering it with foil or something would help in this case (as Waterwingz said too).
Maybe other owners of sx40 could test that and check whether they have the same problem. Have you been using the dark frame substraction?

BTW - E26 is "CaptureTimeOut" or "WBCaptureTimeOut" so I  assume that your camera got bored after few thousands of seconds:)
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Offline philmoz

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Re: Canon SX40HS long expoisure noise problems
« Reply #12 on: 14 / May / 2013, 21:39:31 »
Quote from: Recyclojunk64 on 12 / May / 2013, 11:26:39
Sorry for resurrecting an old thread, but I want to be sure that I have the same issue with my SX40HS before I tear it apart to fix the grounding problem. I have been trying to take some long exposures, but in anything over several minutes produces a mosaic mess such as this example below taken with the lens cap on and dark frame subtraction enabled.

noise seems to almost increase exponentially with higher exposures.
Is this the same sort of problem that other people here have been talking about or is my camera just going psycho on me?

Somethings not right.

Was this the camera JPEG or converted from RAW/DNG? If converted what software did you use?
What was the ambient temperature?

Attached are crops of the JPEG images from my SX40 using the same settings (256sec, F/2.7, ISO3200). The first is with dark frame subtraction on, the second with it off.

Phil.
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Offline Recyclojunk64

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Re: Canon SX40HS long expoisure noise problems
« Reply #13 on: 16 / May / 2013, 08:16:08 »
Nice to see that this kind of extreme noise is not normal for the SX40.

Well, I decided to eliminate any other variables that I thought might be playing a part in it (with regards to CHDK), and installed the stable release version. Previously I had been using the development trunk that I had compiled myself (to get lua native calls enabled). Anyway, here are the results of the first experiment repeated:


Couldn't be bothered annotating/resizing it this time. It is 3200ISO, 2.7f, and 256seconds with dark-frame subtraction enabled. RAW image looks somewhat worse (but much better than the previous result), I assume this is because it does not have dark-frame subtraction enabled though.
BTW those yellow bright spots are from light getting past the lens cover (it was pointed at a ceiling light). I assume that the purple fringe on the right is that amp glow that this thread was started for. I can live with it though.

So now all I have to do is work out why it was giving out those terrible results before. I might have to recompile CHDK with another compiler and see if its still works then. no I guess that would probably have nothing to do with it. Probably some random obscure setting I accidentally enabled when I was playing around with it.

Cheers
« Last Edit: 16 / May / 2013, 08:20:55 by Recyclojunk64 »
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Offline blackhole

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Re: Canon SX40HS long expoisure noise problems
« Reply #14 on: 16 / May / 2013, 08:43:00 »
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It is 3200ISO, 2.7f, and 256seconds
This looks great for such extreme settings. Amp glow you can  easily solved with dark frame.
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Offline waterwingz

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Re: Canon SX40HS long expoisure noise problems
« Reply #15 on: 16 / May / 2013, 09:08:22 »
Quote from: Recyclojunk64 on 16 / May / 2013, 08:16:08
RAW image looks somewhat worse (but much better than the previous result), I assume this is because it does not have dark-frame subtraction enabled though.
I did a little test a while ago - shot two image in the dark (15 second exposure - jpg & dng).  One had dark frame on,  the other had it off.   I put the four results in a composite image and annotated them.  I think  they speak for themselves (click for a larger image) :

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