Dynamic Range & CHDK RAW Bits?

KenO

122

« on: 31 / July / 2012, 11:06:27 »

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Recently have been reading some DYNAMIC RANGE articles
http://www.cambridgeincolour.com/tutorials/dynamic-range.htm
http://www.normankoren.com/digital_tonality.html
http://www.dpreview.com/learn/?/Glossary/Digital_Imaging/dynamic_range_01.htm
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Photo_p014.shtml
http://en.wikipedia.org/wiki/High_dynamic_range_imaging
http://www.anyhere.com/gward/papers/cic98.pdf

Since I have an older CHDK camera that gives a RAW file of ~ 10 bits, wonder if the newer 14 bit CHDK cameras will give an additional 4 bits of usable Dynamic Range?

While have found DSLR reviews comparing RAW Dynamic Range, I have yet to find a RAW Dynamic Range for the various CHDK cameras.

Since most of the CHDK cameras never had a RAW option, I do not expect to find this information in a regular review.

Did some searches using CHDK Dynamic Range but to date have found nothing.

Has anyone seen this information or decided to run some CHDK Dynamic Range tests?

Ken

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outslider

762

Re: Dynamic Range & CHDK RAW Bits?

« Reply #1 on: 31 / July / 2012, 13:15:32 »

One that comes to my mind:

http://chdk.wikia.com/wiki/Samples:_RAW

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KenO

122

Re: Dynamic Range & CHDK RAW Bits?

« Reply #2 on: 31 / July / 2012, 13:17:41 »

Since posting read Review: Nokia 808 PureView

Conclusion - Pros:

Excellent detail resolution in all modes
Very good image quality - detailed, colorful JPEGs
Impressive photographic feature set - controllable ISO, WB, scene modes et al
Generally reliable AF and metering
Automatic white balance works well in all but the trickiest of light
PureView allows 'zoom' without penalty in image quality
Excellent video quality (and sound)

Conclusion - Cons:

Highlight clipping problematic in scenes with wide tonal range
No one-shot HDR/dynamic range expansion function (but bracketing is available)
Metering can be rather wayward in bright light
On-screen histogram only available while exposure compensation dialog is open
Interface somewhat dense in 'creative' mode
Obscure on-screen icons for ND filter and white balance in creative mode
On-screen ISO indication just shows 'M' when any setting other than Auto is selected
Non-optical 'zooming' doesn't allow control over depth of field
No image stabilization in still capture mode
Red-eye can be an issue in flash shots (but red-eye reduction works well)

http://www.dpreview.com/articles/8083837371/review-nokia-808-pureview/5

"Highlight clipping problematic in scenes with wide tonal range" Could not find any information concerning its Dynamic Range? Also seems no RAW option is available.

Ken

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reyalp

13944

Re: Dynamic Range & CHDK RAW Bits?

« Reply #3 on: 31 / July / 2012, 13:19:39 »

AFAIK g1x is the only CHDK camera with a 14 bit sensor. Other recent powershots are 12 bit, but that doesn't necessarily mean there is any additional DR, or even any extra precision: http://chdk.setepontos.com/index.php?topic=2468.msg30570#msg30570

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KenO

122

Re: Dynamic Range & CHDK RAW Bits?

« Reply #4 on: 31 / July / 2012, 13:40:45 »

Hi reyalp,

"AFAIK g1x is the only CHDK camera with a 14 bit sensor." Hoped that the 14 bit sensors would have started to move down market to less expensive Canons.

"Other recent powershots are 12 bit, but that doesn't necessarily mean there is any additional DR, or even any extra precision: http://chdk.setepontos.com/index.php?topic=2468.msg30570#msg30570 "

Thanks for the comments and link!

ewavr said "Some investigations about 12-bit RAW. I inspected pixel values statistics for SX10 using show_stat program....You still think that the 12-bit ADC means 12-bit measurement accuracy?"

I am not that technical to interpret ewayr's data. Am guessing from your comment "powershots are 12 bit, but that doesn't necessarily mean there is any additional DR, or even any extra precision" that there is no real advantage over earlier ~ 10 bit cameras. Am I correct?

Thanks again for your help!

Ken

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KenO

122

Re: Dynamic Range & CHDK RAW Bits?

« Reply #5 on: 31 / July / 2012, 13:44:17 »

Hi outslider,

"One that comes to my mind: http://chdk.wikia.com/wiki/Samples:_RAW"

Thanks for the link but could not find any mention of dynamic range or RAW bits for CHDK cameras. Did I miss this?

Ken

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reyalp

13944

Re: Dynamic Range & CHDK RAW Bits?

« Reply #6 on: 31 / July / 2012, 16:04:08 »

Quote from: KenO on 31 / July / 2012, 13:40:45

Hi reyalp,

"AFAIK g1x is the only CHDK camera with a 14 bit sensor." Hoped that the 14 bit sensors would have started to move down market to less expensive Canons.

G1X is something of a special case, it's sensor is much closer to a DSLR sensor. I wouldn't expect regular P&S to necessarily follow suit, although enhanced DR is something of a marketing feature (e.g. the multi exposure HDR modes, iContrast etc), so it's not out of the question.

Of course, extra bits doesn't necessarily mean more DR, it could be the same range divided into more distinct values.

Quote

I am not that technical to interpret ewayr's data. Am guessing from your comment "powershots are 12 bit, but that doesn't necessarily mean there is any additional DR, or even any extra precision" that there is no real advantage over earlier ~ 10 bit cameras. Am I correct?

I think that statement is correct for ewavrs measurements. However, it's not clear if this applies to all 12 bit cameras, sx10 was one of the first and Canon uses quite a few different sensors.

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KenO

122

Re: Dynamic Range & CHDK RAW Bits?

« Reply #7 on: 03 / August / 2012, 12:40:10 »

Hi reyalp,

"I think that statement is correct for ewavrs measurements. However, it's not clear if this applies to all 12 bit cameras, sx10 was one of the first and Canon uses quite a few different sensors."

Was there a posting for "ewavrs measurements" that discussed what are considered "Good & Bad" measurements for 12 bit cameras? Did a quick read of http://chdk.setepontos.com/index.php?topic=2468.0 but did not find anything.

As previously mentioned I have no technical background concerning this, do you know of any good papers or postings to get up to speed?

Thanks

Ken

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reyalp

13944

Re: Dynamic Range & CHDK RAW Bits?

« Reply #8 on: 03 / August / 2012, 23:11:35 »

Quote from: KenO on 03 / August / 2012, 12:40:10

Was there a posting for "ewavrs measurements" that discussed what are considered "Good & Bad" measurements for 12 bit cameras?

I don't really understand what there is to discuss. ewavr just made a histogram of the raw values, and saw that even though the raw is 12 bit, there are only ~1000 distinct values (equivalent to a 10 bits)

As I said before, this observation was made for one camera, what other cameras do is unknown until someone cares enough to measure them.

Quote

As previously mentioned I have no technical background concerning this, do you know of any good papers or postings to get up to speed?

I don't understand what "this" refers to.

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KenO

122

Re: Dynamic Range & CHDK RAW Bits?

« Reply #9 on: 07 / August / 2012, 11:20:04 »

Hi reyalp,

"I don't really understand what there is to discuss. ewavr just made a histogram of the raw values, and saw that even though the raw is 12 bit, there are only ~1000 distinct values (equivalent to a 10 bits)"

Thanks for answering this question.

"As previously mentioned I have no technical background concerning this" This refers to digital camera bits.

Since posting did some more searches and found
"14-bit A/D Conversion in DIGIC 4 Cameras...The DIGIC 4 image processor’s 14-bit converter (with 16,384 shades per channel) is capable of higher precision when describing the tonal gradations in a scene than less sophisticated 12-bit converters (with only 4,096 shades per channel). This extra image information might be overkill if it weren’t for the advanced CMOS image sensors found on both the EOS 50D and EOS 5D Mark II. The pixels on both of these sensors have improved fill factors and lower read noise than those in previous Canon sensors in their class, with the larger-sized pixels on the EOS 5D Mark II providing low-noise performance that’s a notch better than the EOS 50D at every comparable ISO setting. In combination with the camera’s lower levels of background noise and amplifier noise, the EOS 5D Mark II’s 14-bit A/D converter helps to provide smoother tonal gradations, along with the potential to increase detail in bright highlights with the Highlight Tone Priority option. The EOS 5D Mark II also maintains a slightly higher dynamic range at high ISOs than the EOS 50D and the older EOS 5D it replaces.

The expanded dynamic range provides increased detail in deep shadow areas and a superior ability to open up shadows in post processing without banding and excessive noise. Detail is also improved in highlight regions, but the difference is less noticeable as a result of inherently lower noise levels in bright tones and highlight areas. However, having extra bit depth and detail in highlight areas allows a photographer to adjust exposure and contrast in post processing to reduce blown out areas without blocking up shadow areas...As technology progresses, more and more display devices and printers will be compatible with the higher bit-depth image data captured by the EOS 50D, and EOS 5D Mark II, and similar cameras, and use it to automatically fine tune image quality while taking advantage of expanded dynamic range these cameras offer."
http://learn.usa.canon.com/resources/articles/2011/14-bit_ad_conversion_digic4_article.shtml

As previously mentioned, had hoped that these newer tech developments had begun to be incorporated in the down market P&S cameras.

From the data presented seems this has yet to occur.

Thanks again for your detailed answers!

Ken

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