Strange output from DNG files, JPG are normal - General Help and Assistance on using CHDK stable releases - CHDK Forum
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Strange output from DNG files, JPG are normal

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Offline stalker78

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Strange output from DNG files, JPG are normal
« on: 14 / February / 2012, 14:27:07 »
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Hello again.

I'm playing with making photos in RAW and saving as DNG files. I got very strange output - please see attached files. My camera (SX230HS) is saving two files, in JPG and DNG. JPG looks normal but DNG looks vignetted and distorted - vertical lines are clearly curved (I have more examples).

Why I'm seeing such behaviour and what can I do to avoid it?
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Offline waterwingz

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Re: Strange output from DNG files, JPG are normal
« Reply #1 on: 14 / February / 2012, 14:54:35 »
Quote from: stalker78 on 14 / February / 2012, 14:27:07
Why I'm seeing such behaviour and what can I do to avoid it?
What you are seeing is perfectly normal.  RAW & DNG images are exactly what the camera gets from its sensor - warts & all.   So what you see is what the lens in your camera produces.  The camera processes that data, making various corrections for optical distortions internally and then compresses it into a JPG file format. 

So,  you asked for RAW - you got RAW.  Anything beyond that requires image editing software on your PC.
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Offline outslider

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Re: Strange output from DNG files, JPG are normal
« Reply #2 on: 14 / February / 2012, 16:17:42 »
There should be a wiki page to describe this, since this question appears again and again :)

BTW this can be used for funny effects - you can make a photo with the highest zoom, then change zoom to minimum and then develop RAW you have obtained before. Camera will perform 'correction' as for the present state, not for the state, when RAW was made. This also applies to the other order. The effect is a little simmilar to the fish eye or re-fish eye.
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Offline reyalp

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Re: Strange output from DNG files, JPG are normal
« Reply #3 on: 14 / February / 2012, 16:23:03 »
Quote from: outslider on 14 / February / 2012, 16:17:42
There should be a wiki page to describe this, since this question appears again and again :)
I just added
http://chdk.wikia.com/wiki/FAQ#Q._My_RAW.2FDNG_files_are_distorted.2C_what.27s_wrong.3F

Feel free to add additional details in http://chdk.wikia.com/wiki/Raw
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Offline lordhades

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Re: Strange output from DNG files, JPG are normal
« Reply #4 on: 15 / February / 2012, 14:00:43 »
Hey guys can someone help me with this one. The DNG file that chdk produces in my a3300 is totally purple, the jpeg is normal but the dng isn't. Someone help please.
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Offline lordhades

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Re: Strange output from DNG files, JPG are normal
« Reply #5 on: 15 / February / 2012, 14:02:46 »
This is how it looks like guys. Someone help!
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Offline Microfunguy

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Re: Strange output from DNG files, JPG are normal
« Reply #6 on: 15 / February / 2012, 14:57:04 »
I have not followed the A3300 porting thread but that degree of purple cast normally means the wrong colour-filter array has been specified by the porter.

If not, then it is up to YOU to determine the values for the colour matrix, if you are convinced (for some reason) that the result will be worth the effort.
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Offline fe50

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Re: Strange output from DNG files, JPG are normal
« Reply #7 on: 16 / February / 2012, 01:20:06 »
Quote from: lordhades on 15 / February / 2012, 14:00:43
The DNG file that chdk produces in my a3300 is totally purple, the jpeg is normal but the dng isn't.
Since there are no similar results reported on the A3300 porting thread (http://chdk.setepontos.com/index.php?topic=6972.240), this may be an issue with your image processing software.

You may try another RAW editor, e.g. RawTherapee or XNView for testing; try also different RAW settings in your software, e.g. the white balance setting...

* http://chdk.wikia.com/wiki/Software
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Offline Lebeau

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Re: Strange output from DNG files, JPG are normal
« Reply #8 on: 16 / February / 2012, 10:04:04 »
I don't have A3300 but, for DNG file, I always use Photoshop or Lightroom. You could also find a DNG CODEC to display within Windows Explorer at Adobe Labs, just to be sure of the DNG contents.
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Offline stalker78

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Re: Strange output from DNG files, JPG are normal
« Reply #9 on: 16 / February / 2012, 13:22:46 »
Quote from: waterwingz on 14 / February / 2012, 14:54:35
Quote from: stalker78 on 14 / February / 2012, 14:27:07
Why I'm seeing such behaviour and what can I do to avoid it?
What you are seeing is perfectly normal.  RAW & DNG images are exactly what the camera gets from its sensor - warts & all.   So what you see is what the lens in your camera produces.  The camera processes that data, making various corrections for optical distortions internally and then compresses it into a JPG file format. 

So,  you asked for RAW - you got RAW.  Anything beyond that requires image editing software on your PC.

RAW with such distortion? I have another camera - Nikon D40x - and when I'm taking photos in NEF (internal Nikon RAW format) I got same files as in JPG; maybe slightly different colours which I correct in DCRaw but without any barrel distortion.

I'm really confused...
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