Are there differences between A650IS and G9 RAW? - RAW Shooting and Processing - CHDK Forum

Are there differences between A650IS and G9 RAW?

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Are there differences between A650IS and G9 RAW?
« on: 03 / December / 2008, 05:35:08 »
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Hi,

The RAW files from my A650IS using CHDK were 15,270 KB and a sample RAW file from a G9 was 14,216 KB (not using CHDK, native RAW).  From the various postings on this forum and my search of the internet, my understanding is that the bit depth of each channel of the RAW file for the A650IS is 10 bits while the G9 RAW file bit depth for each channel is 12 bits.

1.  Why are the A650IS RAW files larger than the G9 RAW files if the files contain less bit depth and do not have the EXIF information?
2.  I thought that both cameras use the same sensor.  If this is so, why would the two cameras generate different RAW bit depth files if the RAW files are just unprocessed data from the sensor?
3.  What is the size of the G9 RAW files generated using CHDK?
4.  Are the G9 RAW files generated using CHDK the same as the native G9 RAW files (other than the missing EXIF data)?
5.  Can Adobe Photoshop provide the bit depth per channel information (from a CHDK RAW file converted to DNG) and if not, what software (preferably free) can provide that information?



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Offline vit40

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Re: Are there differences between A650IS and G9 RAW?
« Reply #1 on: 03 / December / 2008, 06:55:14 »
1) Native Canon raw is compressed (jpeg lossless compression - like in compressed dng files). CHDK RAW isn't compressed
2) CCD sensor "generates" analog output values, so I suppose A/D converter in G9 is different, but since noise is higher than rounding error, it doesn't make big difference
4) see 1)
5) bit depth is written in dng, along with other EXIF tags

Re: Are there differences between A650IS and G9 RAW?
« Reply #2 on: 03 / December / 2008, 15:34:59 »
Thanks for replying to my post.

I checked with Adobe Bridge and bit depth is a displayable metadata information.  However, the A650IS DNG file did not have bit depth information.

Is the A/D converter part of the sensor circuitry?

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Offline vit40

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Re: Are there differences between A650IS and G9 RAW?
« Reply #3 on: 04 / December / 2008, 01:47:09 »
From my knowledge, in case of CCD sensor (like in most compact cameras), A/D converter is separate circuitry, while in case of CMOS sensor (in most DSLR-s), you get digital output, so A/D converter is a part of sensor


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Offline dzsemx

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Re: Are there differences between A650IS and G9 RAW?
« Reply #4 on: 04 / December / 2008, 15:44:44 »
i don't think that the g9 works really with 12 bits.
really it has no sense because of noise.
or does it?

 

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