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SX40HS, black ring when shooting RAW

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SX40HS, black ring when shooting RAW
« on: 18 / April / 2014, 15:49:13 »
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Hello, how are you?
I´m new using the CHDK and when I take pictures in RAW when I view on my PC I see a black ring (or black vignette) in the angles. Know what? How can I fix it? (I don´t see it when i am shooting) :( :(

Canon SX40HS
Firmware 100I

Thanks !!!  :)

Re: SX40HS, black ring when shooting RAW
« Reply #1 on: 18 / April / 2014, 16:28:04 »
I attach an image as example

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Offline srsa_4c

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Re: SX40HS, black ring when shooting RAW
« Reply #2 on: 18 / April / 2014, 16:49:30 »
What you see is perfectly normal for your camera, the strong vignetting only appears at wide angle. To see what's happening, compare a camera jpeg with the corresponding raw image. You can get rid of it if you apply some lens distortion correction to your wide angle raw images.
If you're using Adobe products, you can find a user-made lens profile for your cam here.

Re: SX40HS, black ring when shooting RAW
« Reply #3 on: 18 / April / 2014, 21:56:34 »
Thanks for the reply!!
Is there any setting in CHDK menu to avoid this effect?


Re: SX40HS, black ring when shooting RAW
« Reply #4 on: 18 / April / 2014, 22:05:24 »
Thanks for the reply!!  Is there any setting in CHDK menu to avoid this effect?
When you record RAW/DNG images,  you are recording EXACTLY what the image sensor sees.  No corrections. cropping, filtering, or any other changes.  Pure raw image.   

So no,  there is nothing in the CHDK menus that changes this.

Here's some reading on CHDK RAW you might find interesting :
link> CHDK Wiki Page about RAW
link> CHDK Forum thread on RAW
link> CHDK Wiki Page about Raw Software
link> CHDK Forum Board for RAW
link> How do you fix lens distortion with CHDK RAW files?
link> msl’s collection of lens profiles for adobe products
link> Decoding CHDK RAW images from a new cameras
link> rawconvert utility to allow manipulation of CHDK RAW files
link> DNG4PS-2 utility to convert CHDK RAW images to DNG format
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: SX40HS, black ring when shooting RAW
« Reply #5 on: 18 / April / 2014, 22:38:12 »
Thanks for the reply!!
Is there any setting in CHDK menu to avoid this effect?
Not in CHDK, but you can correct it in processing. Some software has vignetting correction, or you can use a flat frame http://chdk.setepontos.com/index.php?topic=10921.msg107098#msg107098
Don't forget what the H stands for.

Re: SX40HS, black ring when shooting RAW
« Reply #6 on: 19 / April / 2014, 00:52:40 »
I will try to remove it in the post processing
Thank you both !

 

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