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Canon XSi Processor and features

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Offline genosmm

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Canon XSi Processor and features
« on: 03 / March / 2008, 18:08:42 »
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Was reading the latest info for Canon XSi.  Canon EOS 450D Rebel XSi Digital Camera - Preview - The Imaging Resource!

Was especially interested in the "Use of the DIGIC III processor allows 14-bit analog to digital image processing, as well as capture of 14-bit RAW files, which promises smoother, more flexible tone curves. We also confirmed that the DIGIC processors are the same chip across the product line, from PowerShot to Canon's Mark III professional cameras: when it says DIGIC III, it's the same processor, just used for different purposes depending on the camera."

Has anyone been able to get "14-bit RAW files" from PowerShot cameras?

Gene
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Offline wontolla

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Re: Canon XSi Processor and features
« Reply #1 on: 04 / March / 2008, 07:59:31 »
Interesting. I guess Canon uses the same DIGIC III processor in DSLR and P&S because it is cheaper to design only one.

If I'm not mistakeing, if the Powershot's sensor outputs 10 bits only, there is nothing the processor can do but process 10 bits only.
« Last Edit: 04 / March / 2008, 08:02:25 by wontolla »
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Offline hydrogen

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Re: Canon XSi Processor and features
« Reply #2 on: 05 / March / 2008, 01:07:19 »
Quote from: wontolla on 04 / March / 2008, 07:59:31
Interesting. I guess Canon uses the same DIGIC III processor in DSLR and P&S because it is cheaper to design only one.

If I'm not mistakeing, if the Powershot's sensor outputs 10 bits only, there is nothing the processor can do but process 10 bits only.

The processor will process 14bits.  The A/D converter in Powershot is only 10bit though.  I think that is where the quality loss occurs.  Maybe CHDK can implement a software A/D converter?

"Another image quality enhancement is the upgrade of the Analog-to-Digital (A/D) conversion process to a 14-bit A/D processor."
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Offline brainwash

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Re: Canon XSi Processor and features
« Reply #3 on: 11 / August / 2008, 10:08:53 »
Well, the cost of DSLRs is being pushed mainly by optics and sensors (and of course the whole mirror-thing). I doubt you will get a difference out of a P&S by increasing the sensor resolution since those bits are designed from the start to not be read. So, optics are cheaper and lower-quality and even the A/D converter is not wired on its lower two bits, check for a thread here that shows the schematic.
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Offline reyalp

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Re: Canon XSi Processor and features
« Reply #4 on: 11 / August / 2008, 15:54:48 »
Quote from: genosmm on 03 / March / 2008, 18:08:42
We also confirmed that the DIGIC processors are the same chip across the product line, from PowerShot to Canon's Mark III professional cameras: when it says DIGIC III, it's the same processor, just used for different purposes depending on the camera."

Has anyone been able to get "14-bit RAW files" from PowerShot cameras?
As others have said, it doesn't mean the sensor, amplifiers and ADC is the same. We know the sensor is very different, and the associated hardware is almost certainly different as well.

All it really means is that DIGIC-III has enough CPU power to deal with that much data, which might indicate it's a little over spec'd for a P&S. OTOH, they don't say that the memory subsystems or clock speeds are the same. If nothing else, I'd suspect the larger, partly metal design of a DSL allows them to clock it quite a bit higher than the subcompacts.
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Offline brainwash

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Re: Canon XSi Processor and features
« Reply #5 on: 11 / August / 2008, 16:32:13 »
My thoughts exactly, but as far as I might guess DIGIC-III might only be a platform, unified processor architecture, which might be powered by different processors. If the processors are identical then probably the P&S will be 'dumbed down' to avoid competing with DSLRs.
In graphic cards usually the R&D comes up with the faster high-end chip and incorporates that into low-end cards to avoid having specific R&D for that.
This also happens in automotive industry with car stereos and such.
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Offline lukg

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Re: Canon XSi Processor and features
« Reply #6 on: 20 / August / 2008, 05:48:56 »
You are right, these are marketing choices to lower costs and for market segmentation at the same time!
But I think that 10bit are enough for P&S with sensors of 1./1.8" - 1/2.5". Noise in these camera is always present (maybe not much noticeable at low iso, but still there), so there's no need to choose a primary color between 16384 values instead of 1024.
Without considering the quantization error always present, a 10bit A/D converter could give "less wrong" result when signal noise is high enough (not too much) for compensate the error with the approximation due to its 10bit limitation.
Obviously if the noise is low or not present a 14bit A/D converter will always provide more accurate results.
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