Long exposure test - Day 1 - page 2 - General Help and Assistance on using CHDK stable releases - CHDK Forum

Long exposure test - Day 1

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Re: Long exposure test - Day 1
« Reply #10 on: 23 / March / 2015, 19:42:19 »
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These are canon RAW files
Well that explains the lens vignetting correction factors applied to your original images. Photoshop RAW and Bridge CS6 both have lens corrections for popular cameras like the SX50.   The image you saw on the upload site are what the actual CR2 flle looks like prior to those corrections.  Although even these image may have some "in camera" correction applied.

As blackhole posted earlier,  it would be quite interesting to see a CHDK DNG image taken the same way.   That would give you some idea of what the sensor is actually producing.  If you get another clear night,  can you enable CHDK DNG and take a shot?  It would be interesting to see the DNG, CR2 and JPG that results.
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline ahmad

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Re: Long exposure test - Day 1
« Reply #11 on: 24 / March / 2015, 11:59:19 »
Quote from: waterwingz
it would be quite interesting to see a CHDK DNG image taken the same way.   That would give you some idea of what the sensor is actually producing.  If you get another clear night,  can you enable CHDK DNG and take a shot?  It would be interesting to see the DNG, CR2 and JPG that results.

YES, I will try several things soon as I get better view


Re: Long exposure test - Day 1
« Reply #13 on: 28 / March / 2015, 11:13:05 »
The DNG's confirm it.  No visible "amp glow" in a 60 second exposure using an SX50.

Nice.
Ported :   A1200    SD940   G10    Powershot N    G16


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Offline reyalp

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Re: Long exposure test - Day 1
« Reply #14 on: 28 / March / 2015, 14:57:46 »
The DNG's confirm it.  No visible "amp glow" in a 60 second exposure using an SX50.

Nice.
FWIW if darkframe subtraction is active (as it is by default for long exposures without CHDK overrides), it will take care of most of the amp glow, at the expense of making each shot take 2x as long as the requested exposure time.

That said, it appears Canon has greatly reduced the amount of amp glow in recent cameras, my elph130 and sx160 both show very little in exposures of a couple minutes. A dark frame is still desirable to get rid of hot pixels normal dark current.

Some examples
https://app.box.com/s/sjj9a6kiyx95qeda9ixubxpkmuhuol3u
3992 is 4 minutes, 3993 is 2 minutes, elph130. Canon DFS was off.

From comparison, 3724 is a 64 second exposure with D10 (note the exif in the canon jpeg says 15 sec but it's wrong :-[) Fuzzy green spot is comet C/2014 Q2 (Lovejoy)

For both cameras, the CRW_*.jpg files are processed in raw therapee, using a separately created dark frame as described in http://chdk.setepontos.com/index.php?topic=10159.msg101969#msg101969

Edit:
Interestingly, someone complained about what appeared to be bad amp glow or something similar on sx50hs in http://chdk.setepontos.com/index.php?topic=11062.0
« Last Edit: 28 / March / 2015, 15:02:03 by reyalp »
Don't forget what the H stands for.

 

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